- Directeur de la Fédération Fabri de Peiresc
- Directeur de l'Institut de Mécanique et Ingénierie
- Membre du Comité Scientifique de l'EUROFUSION - Theory and Advanced Simulation Coordination
- Editorial board Journal of Engineering
Activités
Ecoulements en rotation: Taylor-Couette, rotor-stator, éclatement tourbillonnaire, couches limites,...
Plasmas de tokamak: Modélisation, transport turbulent, plasma de bord
Méthodes numériques d'ordre élevé
Publications scientifiques au M2P2
2024
Jingtao Ma, Lincheng Xu, Jérôme Jacob, Eric Serre, Pierre Sagaut. An averaged mass correction scheme for the simulation of high subsonic turbulent internal flows using a lattice Boltzmann method. Physics of Fluids, 2024, 36 (3), ⟨10.1063/5.0192360⟩. ⟨hal-04514161⟩ Plus de détails...
This paper addresses the simulation of internal high-speed turbulent compressible flows using lattice Boltzmann method (LBM) when it is coupled with the immersed boundary method for non-body-fitted meshes. The focus is made here on the mass leakage issue. The recent LBM pressure-based algorithm [Farag et al. Phys. Fluids 32, 066106 (2020)] has shown its superiority on classical density-based algorithm to simulate high-speed compressible flows. Following our previous theoretical work on incompressible flows [Xu et al. Phys. Fluids 34, 065113 (2022)], we propose an averaged mass correction technique to mitigate mass leakage when simulating high-Mach-number compressible flows. It is adapted to deal here with a density, which is decoupled from the zero-moment definition. The simulations focus on two generic but canonical configurations of more complex industrial devices, the straight channel at different angles of inclination at Mach numbers (Ma) ranging from 0.2 to 0.8, and the National Aeronautics and Space Administration Glenn S-duct at Ma = 0.6. The present results show that mass leakage can be a critical issue for the accuracy of the solution and that the proposed correction technique effectively mitigates it and leads to significant improvements in the prediction of the solution.
Jingtao Ma, Lincheng Xu, Jérôme Jacob, Eric Serre, Pierre Sagaut. An averaged mass correction scheme for the simulation of high subsonic turbulent internal flows using a lattice Boltzmann method. Physics of Fluids, 2024, 36 (3), ⟨10.1063/5.0192360⟩. ⟨hal-04514161⟩
Raffael Düll, Hugo Bufferand, Eric Serre, Guido Ciraolo, Virginia Quadri, et al.. Introducing electromagnetic effects in Soledge3X. Contributions to Plasma Physics, 2024, pp.e202300147. ⟨10.1002/ctpp.202300147⟩. ⟨hal-04474339⟩ Plus de détails...
In the pedestal region, electromagnetic effects affect the evolution of micro‐instabilities and plasma turbulence. The transport code Soledge3X developed by the CEA offers an efficient framework for turbulent 3D simulation on an electrostatic model with a fixed magnetic field. The physical accuracy of the model is improved with electromagnetic induction, driven by the local value of the parallel component of the electromagnetic vector potential , known from Ampère's law. It is solved implicitly in a coupled system with the vorticity equation on the electric potential . The consequence is a basic electromagnetic behavior in the form of shear Alfvén waves. A finite electron mass prevents unphysical speeds but requires solving for the time evolution of the parallel current density in the generalized Ohm's law. This term can be analytically included with little computational overhead in the system on and and improves its numerical condition, facilitating the iterative solving procedure. Simulations on a periodic slab case let us observe the predicted bifurcation of the wave propagation speed between the Alfvén wave and the electron thermal wave speeds for varying perpendicular wavenumbers. The first results on a circular geometry with a limiter attest to the feasibility of turbulent electromagnetic scenarios.
Raffael Düll, Hugo Bufferand, Eric Serre, Guido Ciraolo, Virginia Quadri, et al.. Introducing electromagnetic effects in Soledge3X. Contributions to Plasma Physics, 2024, pp.e202300147. ⟨10.1002/ctpp.202300147⟩. ⟨hal-04474339⟩
Frédéric Schwander, Eric Serre, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih. Global fluid simulations of edge plasma turbulence in tokamaks: a review. Computers and Fluids, 2024, 270, pp.106141. ⟨10.1016/j.compfluid.2023.106141⟩. ⟨hal-04352255⟩ Plus de détails...
With ITER, the largest tokamak ever built, and the growing number of fusion energy startups in the world, the need for numerical simulations has never been more crucial to progress towards the successful operation of fusion reactors. From fundamental plasma physics to engineering, a hierarchy of models exists from high-fidelity (gyro-)kinetic models in (5D) 6D to 0D fluid transport models. In this paper, we review the state-of-the-art of 3D turbulence fluid simulations in edge tokamak configurations. The widely used drift-reduced Braginskii equations are introduced together with the dedicated boundary conditions modelling plasma wall interactions. If until recently most of the models were focused on electrostatic turbulence driven by interchange-like instabilities, in recent years models have incorporated electromagnetic effects allowing fluctuations of the magnetic field. Specific features of the edge plasma configurations, which make these equations specially challenging to resolve and stressful for the numerical methods, are detailed. In particular, the strong anisotropy of the flow as well as the complex geometric characteristics lead to the development of dedicated discretization schemes and meshing, which are implemented in state-of-the-art codes reviewed here. It appears that the latter can be differentiated by their mesh construction as well by the manner in which they handle parallel gradients (aligned or not along the magnetic field). The review shows that no consensus on the optimal combination between meshing and discretization schemes, if it exists, has been found. Finally, examples of recent achievements show that 3D turbulence simulations of medium-sized tokamaks are currently achievable, but that ITERsize tokamaks and thermonuclear plasmas still require significant progress.
Frédéric Schwander, Eric Serre, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih. Global fluid simulations of edge plasma turbulence in tokamaks: a review. Computers and Fluids, 2024, 270, pp.106141. ⟨10.1016/j.compfluid.2023.106141⟩. ⟨hal-04352255⟩
L. Cappelli, N. Fedorczak, J. P. Gunn, S. Di Genova, J. Guterl, et al.. Study of the erosion and redeposition of W considering the kinetic energy distribution of incident ions through a semi-analytical model. Plasma Physics and Controlled Fusion, 2023, 65 (9), pp.095001. ⟨10.1088/1361-6587/ace282⟩. ⟨hal-04190861⟩ Plus de détails...
In today’s nuclear fusion devices, erosion of high-Z metallic plasma-facing materials (PFMs) is mainly caused by physical sputtering. That is, by the exchange of energy between plasma ions and the atoms in the walls. In most of the numerical codes currently in use impinging plasma is approximated as a fluid. By averaging the incident particles’ energy distribution the high-energy population of the eroded material is underestimated. For heavy materials such as W, high-energy eroded particles tend to ionize far from the wall and they are less affected by the sheath electric field hence, not being attracted back to the wall, they have a higher chance to contaminate the core plasma. This could in turn result in an underestimation of the net erosion sources. In this work, a semi-analytical model was developed to include the energy distribution of the incident particles. Then, by Monte Carlo method, the net erosion of tungsten from a smooth PFM was calculated. The results show that the kinetic description in energy is important only for incident particles ionized once. For instance, it is particularly important for plasma ions such as Deuterium. It is seen that Deuterium contribution to the W net sources is not always negligible if compared to light impurities or to tungsten self-sputtering in the range of plasma parameters tested. Finally, results show that the difference between the fluid and kinetic models becomes more pronounced for high-screening plasma conditions.
L. Cappelli, N. Fedorczak, J. P. Gunn, S. Di Genova, J. Guterl, et al.. Study of the erosion and redeposition of W considering the kinetic energy distribution of incident ions through a semi-analytical model. Plasma Physics and Controlled Fusion, 2023, 65 (9), pp.095001. ⟨10.1088/1361-6587/ace282⟩. ⟨hal-04190861⟩
Richard M Lueptow, Rainer Hollerbach, Eric Serre. Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper: part 1. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2023, 381 (2243), ⟨10.1098/rsta.2022.0140⟩. ⟨hal-03989060⟩ Plus de détails...
In 1923, the Philosophical Transactions published G. I. Taylor’s seminal paper on the stability of what we now call Taylor–Couette flow. In the century since the paper was published, Taylor’s ground-breaking linear stability analysis of fluid flow between two rotating cylinders has had an enormous impact on the field of fluid mechanics. The paper’s influence has extended to general rotating flows, geophysical flows and astrophysical flows, not to mention its significance in firmly establishing several foundational concepts in fluid mechanics that are now broadly accepted. This two-part issue includes review articles and research articles spanning a broad range of contemporary research areas, all rooted in Taylor’s landmark paper. This article is part of the theme issue ‘Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper (part 1)’.
Richard M Lueptow, Rainer Hollerbach, Eric Serre. Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper: part 1. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2023, 381 (2243), ⟨10.1098/rsta.2022.0140⟩. ⟨hal-03989060⟩
Journal: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Rainer Hollerbach, Richard M Lueptow, Eric Serre. Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper: part 2. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2023, 381 (2246), ⟨10.1098/rsta.2022.0359⟩. ⟨hal-04057399⟩ Plus de détails...
In 1923, the Philosophical Transactions published G. I. Taylor’s seminal paper on the stability of what we now call Taylor–Couette flow. In the century since the paper was published, Taylor’s ground-breaking linear stability analysis of fluid flow between two rotating cylinders has had an enormous impact on the field of fluid mechanics. The paper’s influence has extended to general rotating flows, geophysical flows and astrophysical flows, not to mention its significance in firmly establishing several foundational concepts in fluid mechanics that are now broadly accepted. This two-part issue includes review articles and research articles spanning a broad range of contemporary research areas, all rooted in Taylor’s landmark paper. This article is part of the theme issue ‘Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper (part 2)’.
Rainer Hollerbach, Richard M Lueptow, Eric Serre. Taylor–Couette and related flows on the centennial of Taylor’s seminal Philosophical Transactions paper: part 2. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2023, 381 (2246), ⟨10.1098/rsta.2022.0359⟩. ⟨hal-04057399⟩
Journal: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
S. Di Genova, G. Ciraolo, A. Gallo, J. Romazanov, N. Fedorczak, et al.. First 3D modeling of tungsten erosion and migration in WEST discharges adopting a toroidally non-symmetric wall geometry. Nuclear Materials and Energy, 2023, 34, pp.101340. ⟨10.1016/j.nme.2022.101340⟩. ⟨hal-03988791⟩ Plus de détails...
Numerical analyses are a key tool to investigate tungsten (W) sources and contamination in W Environment steady-state tokamak (WEST) plasma discharges. Modelling activity was performed in order to study W erosion and migration at WEST plasma-facing components (PFCs), using for the first time a toroidally asymmetric wall geometry provided by toroidally localized objects representing WEST outer limiter or antennae. 3D non-axisymmetric SOLEDGE transport simulations were performed with simplifying assumptions (pure Deuterium plasma, fluid model for neutrals) to reproduce WEST boundary plasma, and used as background for ERO2.0 simulations modelling W erosion, re-deposition, and migration. On the sides of the toroidally localized limiters/antennae, two thin W stripes were considered in order to model WEST W antennae protections. Simulations suggest antennae protections contribution to dominate W contamination in the considered simulations settings, highlighting the need of further analyses with different configurations using this kind of tools.
S. Di Genova, G. Ciraolo, A. Gallo, J. Romazanov, N. Fedorczak, et al.. First 3D modeling of tungsten erosion and migration in WEST discharges adopting a toroidally non-symmetric wall geometry. Nuclear Materials and Energy, 2023, 34, pp.101340. ⟨10.1016/j.nme.2022.101340⟩. ⟨hal-03988791⟩
Ivan Kudashev, Anna Medvedeva, Nicolas Fedorszak, David Zarzoso, Manuel Scotto d’ Abusco, et al.. Development of a set of synthetic diagnostics for the WEST tokamak to confront 2D transport simulations and experimental data. Journal of Instrumentation, 2023, 18 (02), pp.C02058. ⟨10.1088/1748-0221/18/02/C02058⟩. ⟨hal-04010344⟩ Plus de détails...
Significant scientific effort has been focused on optimizing the scenarios and plasma parameters for tokamak operations. The lack of comprehensive understanding of underlying physical processes leads to simplifications used both in plasma simulation codes and for diagnostics, which is also complicated by the harsh plasma environment. One of the main tools to couple, check and verify these assumptions are the synthetic diagnostics. In this work we demonstrate current results of the development of the set of synthetic diagnostics for the WEST tokamak to couple experimental data with the SolEdge3X-HDG 2D transport code.
Ivan Kudashev, Anna Medvedeva, Nicolas Fedorszak, David Zarzoso, Manuel Scotto d’ Abusco, et al.. Development of a set of synthetic diagnostics for the WEST tokamak to confront 2D transport simulations and experimental data. Journal of Instrumentation, 2023, 18 (02), pp.C02058. ⟨10.1088/1748-0221/18/02/C02058⟩. ⟨hal-04010344⟩
Thomas Cartier-Michaud, Philippe Ghendrih, Virginie Grandgirard, Eric Serre. Verification and accuracy check of simulations with PoPe and iPoPe. Journal of Computational Physics, 2023, 474, pp.111759. ⟨10.1016/j.jcp.2022.111759⟩. ⟨hal-03871954⟩ Plus de détails...
The theoretical background of the PoPe and iPoPe verification scheme is presented. Verification is performed using the simulation output of production runs. The computing overhead is estimated to be at most 10%. PoPe or iPoPe calculations can be done offline provided the necessary data is stored, for example additional time slices, or online where iPoPe is more effective. The computing overhead is mostly that of storing the necessary data. The numerical error is determined and split into a part proportional to the operators, which are combined to form the equations to be solved, thus modifying their control parameters, completed by a residual error orthogonal to these operators. The accuracy of the numerical solution is determined by this modification of the control parameters. The PoPe and iPoPe methods are illustrated in this paper with simulations of a simple mechanical system with chaotic trajectories evolving into a strange attractor with sensitivity to initial conditions. We show that the accuracy depends on the particular simulation both because the properties of the numerical solution depend on the values of the control parameter, and because the target accuracy will depend on the problem that is addressed. One shows that for a case close to bifurcations between different states, the accuracy is determined by the level of detail of the bifurcation phenomena one aims at describing. A unique verification index, the PoPe index, is proposed to characterise the accuracy, and consequently the verification, of each production run. The PoPe output allows one to step beyond verification and analyse for example the numerical scheme efficiency. For the chosen example at fixed PoPe index, therefore at fixed numerical error, one finds that the higher order integration scheme, comparing order 4 to order 2 Runge-Kutta time stepping, reduces the computation cost by a factor 4.
Thomas Cartier-Michaud, Philippe Ghendrih, Virginie Grandgirard, Eric Serre. Verification and accuracy check of simulations with PoPe and iPoPe. Journal of Computational Physics, 2023, 474, pp.111759. ⟨10.1016/j.jcp.2022.111759⟩. ⟨hal-03871954⟩
D. Martinand, E. Serre, B. Viaud. Instabilities and routes to turbulence in rotating disc boundary layers and cavities. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2023, 381 (2243), pp.20220135. ⟨10.1098/rsta.2022.0135⟩. ⟨hal-03989074⟩ Plus de détails...
Studied for more than a century, first in the field of geophysics, flows over rotating discs present a great diversity of complex instability behaviours that are not yet fully understood. While the primary instabilities are now well characterized experimentally, theoretically and numerically, their role in the transition mechanisms to turbulence remains an open question that still challenges the scientific community. This article brings together the main results of the literature related to the instabilities over rotating discs, but also in the connected problem of rotating cavities, and reviews the main scenarios currently assumed to describe the flow breakdown to turbulence. A particular focus is on more recent studies of generic flows in rotating cavities bounded by two coaxial rotating discs, that occur in many industrial systems, the performances of which and their improvement are linked to a better understanding of these mechanisms. This article is part of the theme issue ‘Taylor–Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (part 1)’.
D. Martinand, E. Serre, B. Viaud. Instabilities and routes to turbulence in rotating disc boundary layers and cavities. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2023, 381 (2243), pp.20220135. ⟨10.1098/rsta.2022.0135⟩. ⟨hal-03989074⟩
Journal: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Philippe Ghendrih, Guilhem Dif-Pradalier, Olivier Panico, Yanick Sarazin, Hugo Bufferand, et al.. Role of avalanche transport in competing drift wave and interchange turbulence. Journal of Physics: Conference Series, 2022, 2397 (1), pp.012018. ⟨10.1088/1742-6596/2397/1/012018⟩. ⟨hal-04498387⟩ Plus de détails...
Abstract We complete the 2D 2-fields turbulence model previously used with an interchange-like instability by slightly modifying the parallel loss terms to drive drift wave instabilities. We show that the instability driven by temperature fluctuations of the sheath losses is identical to that of the drift wave turbulence. The linear analysis is performed and used to select control parameters that yield identical maximum growth rates for the interchange alone and drift wave alone instability. Combining the two instabilities doubles the maximum growth rate. The non-linear simulations are used to analyse the SOL width. The simulations allow one to identify a low field side SOL region where interchange and drift wave are unstable and a high field side SOL region where only the drift wave is unstable. The SOL profiles appear exponential in the region close to the source but depart from a simple exponential fall-off in the far SOL. The low field side SOL width is found to be larger in the interchange alone case, slightly smaller when both instabilities are present and finally narrower when only the drift waves. For the high field side SOL, without interchange, the drift wave SOL width is observed to be identical to that on the low field side and larger than that when both instabilities at play. The Sherwood dimensionless parameter, ratio of convective particle flux divided by the diffusive particle flux, is used to compare the efficiency of turbulent transport. The profiles of the Sherwood parameter for time and flux surface averaged transport indicate that turbulent transport is dominant close to the separatrix but is less effective towards the far SOL. The Sherwood parameter evolution, determined with the flux-surface averaged transport, indicates that outward avalanche transport with corrugations governs the case with interchange only. When combining the two instabilities, outward avalanche transport is less pronounced and inward avalanche transport is observed, reducing the overall turbulent transport efficiency. The avalanche transport with drift waves only compared to interchange only is found to be inhibited.
Philippe Ghendrih, Guilhem Dif-Pradalier, Olivier Panico, Yanick Sarazin, Hugo Bufferand, et al.. Role of avalanche transport in competing drift wave and interchange turbulence. Journal of Physics: Conference Series, 2022, 2397 (1), pp.012018. ⟨10.1088/1742-6596/2397/1/012018⟩. ⟨hal-04498387⟩
Ivan Kudashev, Anna Medvedeva, Manuel Scotto D’abusco, Nicolas Fedorszak, Stefano Di Genova, et al.. Development of a set of synthetic diagnostics for the confrontation between 2D transport simulations and WEST tokamak experimental data. Applied Sciences, 2022, 12 (19), pp.9807. ⟨10.3390/app12199807⟩. ⟨hal-03982630⟩ Plus de détails...
Transport codes are frequently used for describing fusion plasmas with the aim to prepare tokamak operations. Considering novel codes, such as SolEdge3X-HDG, synthetic diagnostics are a common technique used to validate new models and confront them with experimental data. The purpose of this study is to develop a set of synthetic diagnostics, starting from bolometer and visible cameras for the WEST tokamak, in order to compare the code results with the experimental data. This research is done in the framework of Raysect and Cherab Python libraries. This allows us to process various synthetic diagnostics in the same fashion in terms of 3D ray tracing with volume emitters developed specifically for fusion plasmas. We were able to implement the WEST tokamak model and the design of bolometer and visible cameras. Synthetic signals, based on full-discharge WEST plasma simulation, were used for to compare the SolEdge3X-HDG output plasma with experimental data. The study also considers the optical properties of the plasma-facing components (PFCs) and their influence on the performance of diagnostics. The paper shows a unified approach to synthetic diagnostic design, which will be further extended to cover the remaining diagnostics on the WEST tokamak.
Ivan Kudashev, Anna Medvedeva, Manuel Scotto D’abusco, Nicolas Fedorszak, Stefano Di Genova, et al.. Development of a set of synthetic diagnostics for the confrontation between 2D transport simulations and WEST tokamak experimental data. Applied Sciences, 2022, 12 (19), pp.9807. ⟨10.3390/app12199807⟩. ⟨hal-03982630⟩
D Auroux, P Ghendrih, L Lamerand, F Rapetti, E Serre. Asymptotic behaviour, non-local dynamics and data assimilation tailoring of the reduced κ − ε model to address turbulent transport of fusion plasmas. Physics of Plasmas, 2022. ⟨hal-03811621⟩ Plus de détails...
The high-dimensional and multiscale nature of fusion plasma flows require the development of reduced models to be implemented in numerical codes capable of capturing the main features of turbulent transport in a sufficiently short time to be useful during tokamak operation. This paper goes further in the analysis of the dynamics of the κ − ε model based on the turbulent kinetic energy κ and its dissipation rate ε [Baschetti et al., Nuc. Fus 61, 106020 (2021)] to improve the predictability of the transverse turbulent transport in simulation codes. Present 1D results show further capabilities with respect to current models (based on constant effective perpendicular diffusion) and on the standard quasi-linear approach. The nonlinear dependence of D in κ and ε estimated from two additional transport equations allow to introduce some non-locality in the transport model. This is illustrated by the existence of parameter ranges with turbulence spreading. The paper also addresses another issue related to the uncertainties on the inherent free parameters of such reduced model. The study proposes a new approach in the fusion community based on a variational data assimilation involving the minimisation of a cost function defined as the distance between the reference data and the calculated values. The results are good, and show the ability of the data assimilation to reduce uncertainties on the free parameters, which remains a critical point to ensure the total reliability of such an approach.
D Auroux, P Ghendrih, L Lamerand, F Rapetti, E Serre. Asymptotic behaviour, non-local dynamics and data assimilation tailoring of the reduced κ − ε model to address turbulent transport of fusion plasmas. Physics of Plasmas, 2022. ⟨hal-03811621⟩
Guanxiong Wang, Song Zhao, Pierre Boivin, Eric Serre, Pierre Sagaut. A new hybrid lattice-Boltzmann method for thermal flow simulations in low-Mach number approximation. Physics of Fluids, 2022, 34 (4), pp.046114. ⟨10.1063/5.0091517⟩. ⟨hal-03796386⟩ Plus de détails...
A new low-Mach algorithm for the thermal lattice Boltzmann method (LBM) is proposed aiming at reducing the computational cost of thermal flow simulations in the low Mach number limit. The well-known low Mach number approximation is adopted to accelerate the simulations by enlarging the time step through re-scaling the psuedoacoustic speed to the same order of the fluid motion velocity. This specific process is inspired by the similarity between the artificial compressibility method and the isothermal LBM and is further extended to its thermal counterpart. It must be emphasized that such low-Mach acceleration strategy is in a general form, thus can be easily applied to other compressible LB methods. The present method overcomes the drawback of the classical pressure gradient scaling method due to the pressure gradient changing. The new algorithm is validated by various well-documented academic test cases in laminar [one dimensional gravity column, 2D (two dimensional) rising thermal bubble, and 2D differentially heated square cavity] and turbulent [3D (three dimensional) Taylor–Green vortex and 3D heated cylinder] regimes. All the results show excellent agreement with the reference data and high computational efficiency.
Guanxiong Wang, Song Zhao, Pierre Boivin, Eric Serre, Pierre Sagaut. A new hybrid lattice-Boltzmann method for thermal flow simulations in low-Mach number approximation. Physics of Fluids, 2022, 34 (4), pp.046114. ⟨10.1063/5.0091517⟩. ⟨hal-03796386⟩
H Bufferand, J Balbin, S Baschetti, J Bucalossi, G Ciraolo, et al.. Implementation of multi-component Zhdanov closure in SOLEDGE3X. Plasma Physics and Controlled Fusion, 2022, 64 (5), pp.055001. ⟨10.1088/1361-6587/ac4fac⟩. ⟨hal-03981783⟩ Plus de détails...
The multi-component fluid closure derived by Zhdanov (2002 Transport Processes in Multicomponent Plasma (London: Taylor and Francis)) is implemented in the fluid code SOLEDGE3X-EIRENE to deal with arbitrary edge plasma composition. The closure assumes no distinction between species such as light versus heavy species separation. The work of Zhdanov is rewritten in a matricial form in order to clearly link friction forces and heat fluxes to the different species velocities and temperature gradients.
H Bufferand, J Balbin, S Baschetti, J Bucalossi, G Ciraolo, et al.. Implementation of multi-component Zhdanov closure in SOLEDGE3X. Plasma Physics and Controlled Fusion, 2022, 64 (5), pp.055001. ⟨10.1088/1361-6587/ac4fac⟩. ⟨hal-03981783⟩
M Raghunathan, Y Marandet, H Bufferand, G Ciraolo, Ph Ghendrih, et al.. Multi-temperature Generalized Zhdanov Closure for Scrape-Off Layer/Edge Applications. Plasma Physics and Controlled Fusion, 2022. ⟨hal-03810579⟩ Plus de détails...
The derivation of the multi-temperature generalized Zhdanov closure is provided starting from the most general form of the left hand side of the moment averaged kinetic equation with the Sonine-Hermite polynomial ansatz for an arbitrary number of moments. The process of arriving at the reduced higher-order moment equations, with its assumptions and approximations, is explicitly outlined. The generalized multi-species, multi-temperature coefficients from the authors' previous article are used to compute values of higher order moments such as heat flux in terms of the lower order moments. Transport coefficients and the friction and thermal forces for magnetic confinement fusion relevant cases with the generalized coefficients are compared to the scheme with the single-temperature coefficients previously provided by Zhdanov et al. It is found that the 21N-moment multi-temperature coefficients are adequate for most cases relevant to fusion. Furthermore, the 21N-moment scheme is also tested against the trace approximation to determine the range of validity of the trace approximation with respect to fusion relevant plasmas. Possible refinements to the closure scheme are illustrated as well, in order to account for quantities which might be significant in certain schemes such as the drift approximation.
M Raghunathan, Y Marandet, H Bufferand, G Ciraolo, Ph Ghendrih, et al.. Multi-temperature Generalized Zhdanov Closure for Scrape-Off Layer/Edge Applications. Plasma Physics and Controlled Fusion, 2022. ⟨hal-03810579⟩
X Litaudon, F Jenko, D Borba, D Borodin, B J Braams, et al.. EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing. Plasma Physics and Controlled Fusion, 2022, 64 (3), pp.034005. ⟨10.1088/1361-6587/ac44e4⟩. ⟨hal-03562886⟩ Plus de détails...
Abstract This paper is a written summary of an overview oral presentation given at the 1st Spanish Fusion High Performance Computer (HPC) Workshop that took place on the 27 November 2020 as an online event. Given that over the next few years ITER 24 24 ITER (‘The Way’ in Latin) is the world’s largest tokamak under construction in the south of France: a magnetic fusion device that has been designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy ( https://www.iter.org/ ). will move to its operation phase and the European-DEMO design will be significantly advanced, the EUROfusion consortium has initiated a coordination effort in theory and advanced simulation to address some of the challenges of the fusion research in Horizon EUROPE (2021–2027), i.e. the next EU Framework Programme for Research and Technological Development. This initiative has been called E-TASC, which stands for EUROfusion-Theory and Advanced Simulation Coordination. The general and guiding principles of E-TASC are summarized in this paper. In addition, an overview of the scientific results obtained in the pilot phase (2019–2020) of E-TASC are provided while highlighting the importance of the required progress in computational methods and HPC techniques. In the initial phase, five pilot theory and simulation tasks were initiated: towards a validated predictive capability of the low to high transition and pedestal physics; runaway electrons in tokamak disruptions in the presence of massive material injection; fast code for the calculation of neoclassical toroidal viscosity in stellarators and tokamaks; development of a neutral gas kinetics modular code; European edge and boundary code for reactor-relevant devices. In this paper, we report on recent progress made by each of these projects.
X Litaudon, F Jenko, D Borba, D Borodin, B J Braams, et al.. EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing. Plasma Physics and Controlled Fusion, 2022, 64 (3), pp.034005. ⟨10.1088/1361-6587/ac44e4⟩. ⟨hal-03562886⟩
D. Galassi, C. Theiler, T. Body, F. Manke, P. Micheletti, et al.. Validation of edge turbulence codes in a magnetic X-point scenario in TORPEX. Physics of Plasmas, 2022, 29 (1), pp.012501. ⟨10.1063/5.0064522⟩. ⟨hal-03566373⟩ Plus de détails...
D. Galassi, C. Theiler, T. Body, F. Manke, P. Micheletti, et al.. Validation of edge turbulence codes in a magnetic X-point scenario in TORPEX. Physics of Plasmas, 2022, 29 (1), pp.012501. ⟨10.1063/5.0064522⟩. ⟨hal-03566373⟩
M Scotto d'Abusco, G Giorgiani, J F Artaud, H Bufferand, G Ciraolo, et al.. Core-edge 2D fluid modeling of full tokamak discharge with varying magnetic equilibrium: from WEST start-up to ramp-down. Nuclear Fusion, 2022, ⟨10.1088/1741-4326/ac47ad⟩. ⟨hal-03509800⟩ Plus de détails...
In the present work we investigate for the first time the 2D fluid transport of the plasma in WEST during an entire discharge from the start-up to the ramp-down (shot #54487). The evolution of density profile, electron and ion temperatures together with the experimental magnetic equilibrium, total current and gas-puff rate is investigated. Comparisons with the interferometry diagnostic show a remarkable overall qualitative agreement during the discharge that can be quantitative at some locations in the plasma core. If at the onset of the X-points during the ramp-up the electron heat flux is dominant at the target, present results show that the ion heat flux becomes dominant during the stationary phase of the discharge. Using a simple model for erosion, present results assess the tungsten sputtering due to deuterium ions during the start-up and ramp-up phases of the discharge and confirms the need to consider full discharge simulation to accurately treat the W source of contamination. This work also demonstrates the interest of developing magnetic equilibrium free solver including efficient time integration to step toward predictive capabilities in the future for fusion operation.
M Scotto d'Abusco, G Giorgiani, J F Artaud, H Bufferand, G Ciraolo, et al.. Core-edge 2D fluid modeling of full tokamak discharge with varying magnetic equilibrium: from WEST start-up to ramp-down. Nuclear Fusion, 2022, ⟨10.1088/1741-4326/ac47ad⟩. ⟨hal-03509800⟩
D.S. Oliveira, T. Body, D. Galassi, C. Theiler, E. Laribi, et al.. Validation of edge turbulence codes against the TCV-X21 diverted L-mode reference case. Nuclear Fusion, 2022, 62 (9), pp.096001. ⟨10.1088/1741-4326/ac4cde⟩. ⟨hal-03740877⟩ Plus de détails...
Self-consistent full-size turbulent-transport simulations of the divertor and scrape-off-layer (SOL) of existing tokamaks have recently become feasible. This enables the direct comparison of turbulence simulations against experimental measurements. In this work, we perform a series of diverted ohmic L-mode discharges on the tokamak à configuration variable (TCV) tokamak, building a first-of-a-kind dataset for the validation of edge turbulence models. This dataset, referred to as TCV-X21 , contains measurements from five diagnostic systems from the outboard midplane (OMP) to the divertor targets—giving a total of 45 one- and two-dimensional comparison observables in two toroidal magnetic field directions. The experimental dataset is used to validate three flux-driven 3D fluid-turbulence models—GBS, GRILLIX and TOKAM3X. With each model, we perform simulations of the TCV-X21 scenario, individually tuning the particle and power source rates to achieve a reasonable match of the upstream separatrix value of density and electron temperature. We find that the simulations match the experimental profiles for most observables at the OMP—both in terms of profile shape and absolute magnitude—while a comparatively poorer agreement is found towards the divertor targets. The match between simulation and experiment is seen to be sensitive to the value of the resistivity, the heat conductivities, the power injection rate and the choice of sheath boundary conditions. Additionally, despite targeting a sheath-limited regime, the discrepancy between simulations and experiment also suggests that the neutral dynamics should be included. The results of this validation show that turbulence models are able to perform simulations of existing devices and achieve reasonable agreement with experimental measurements. Where disagreement is found, the validation helps to identify how the models can be improved. By publicly releasing the experimental dataset and validation analysis, this work should help to guide and accelerate the development of predictive turbulence simulations of the edge and SOL.
D.S. Oliveira, T. Body, D. Galassi, C. Theiler, E. Laribi, et al.. Validation of edge turbulence codes against the TCV-X21 diverted L-mode reference case. Nuclear Fusion, 2022, 62 (9), pp.096001. ⟨10.1088/1741-4326/ac4cde⟩. ⟨hal-03740877⟩
Guanxiong Wang, Song Zhao, Pierre Boivin, Eric Serre, Pierre Sagaut. A new hybrid Lattice-Boltzmann method for thermal flow simulations in low-Mach number approximation. Physics of Fluids, 2022, Physics of fluids, 34 (046114). ⟨hal-03636905⟩ Plus de détails...
Guanxiong Wang, Song Zhao, Pierre Boivin, Eric Serre, Pierre Sagaut. A new hybrid Lattice-Boltzmann method for thermal flow simulations in low-Mach number approximation. Physics of Fluids, 2022, Physics of fluids, 34 (046114). ⟨hal-03636905⟩
Giacomo Piraccini, Marcello Capasso, Manuel Scotto d'Abusco, Giorgio Giorgiani, Frédéric Schwander, et al.. Recent upgrades in a 2D turbulent transport solver based on a hybrid discontinuous Galerkin method for the simulation of fusion plasma in tokamak. Fluids, 2022, ⟨10.3390/fluids7020063⟩. ⟨hal-03562497⟩ Plus de détails...
The simulation of fusion plasmas in realistic magnetic configurations and tokamak ge-1 ometries still requires the development of advanced numerical algorithms owing to the complexity 2 of the problem. In this context, we propose a Hybrid Discontinuous Galerkin (HDG) method to 3 solve 2D transport fluid equations in realistic magnetic and tokamak wall geometries. This high-4 order solver can handle magnetic equilibrium free structured and unstructured meshes allowing a 5 much more accurate discretization of the plasma facing components than current solvers based 6 on magnetic field aligned methods associated to finite-differences (volumes) discretization. In 7 addition, the method allows to handle realistic magnetic equilibrium, eventually non steady, a 8 critical point in the modelling of full discharges including ramp up and ramp down phases. In 9 this paper, we introduce the HDG algorithm with a special focus on recent developments related 10 to the treatment of the cross-field diffusive terms, and to an adaptive mesh refinement technique 11 improving the numerical efficiency and robustness of the scheme. The updated solver is verified 12 with a manufactured solution method, and numerical tests are provided to illustrate the new 13 capabilities of the code.
Giacomo Piraccini, Marcello Capasso, Manuel Scotto d'Abusco, Giorgio Giorgiani, Frédéric Schwander, et al.. Recent upgrades in a 2D turbulent transport solver based on a hybrid discontinuous Galerkin method for the simulation of fusion plasma in tokamak. Fluids, 2022, ⟨10.3390/fluids7020063⟩. ⟨hal-03562497⟩
Lincheng Xu, Eric Serre, Pierre Sagaut. A theoretical analysis of mass leakage at boundaries within the lattice Boltzmann method. Physics of Fluids, 2022, Physics of fluids, 34 (065113). ⟨hal-03683744⟩ Plus de détails...
Mass leakage at boundaries can be a critical issue for reliability of the lattice Boltzmann (LB) method based on Cartesian grids. Despite numerous work based on the LB method, the intrinsic macroscopic mechanisms causing mass leakage are still not fully charac- terised, but are essential to improve the mass conservation of LB simulations. In this paper, an original theoretical investigation of mass leakage at boundaries is proposed within the general LB framework. It is demonstrated that the mass leakage originates from the in- trinsic deficiency of the wall-cut LB links at boundary nodes in recovering macroscopic momenta. From a mesoscopic-level definition, i.e. the net loss of distribution functions during the streaming process, the local mass leakage at individual boundary nodes and its averaged value along smooth boundaries are mathematically expressed using macroscopic variables. The local mass leakage is shown to be dominated by terms proportional to the tangential momentum component. In contrast, the averaged mass leakage is shown to be contributed from various terms including the boundary curvature, the tangential momen- tum, and the gradients of density, momentum and momentum flux. Meanwhile, amplitude of the averaged mass leakage is theoretically estimated to be proportional to the local grid spacing, based on which a first-order accurate correction scheme is proposed. In addition, both the local and averaged mass leakage are demonstrated to be significantly dependent on boundary orientation with respect to the grid. The proposed theoretical analysis is assessed by performing numerical experiments. Two-dimensional weakly compressible flows through straight and curved moving channels are considered to estimate each term appearing in the theoretical analysis. The numerical results are in very good agreement with the proposed analysis, and the proposed mass correction scheme based on the av- eraged mass leakage effectively cures the mass leakage problems in the considered test cases.
Lincheng Xu, Eric Serre, Pierre Sagaut. A theoretical analysis of mass leakage at boundaries within the lattice Boltzmann method. Physics of Fluids, 2022, Physics of fluids, 34 (065113). ⟨hal-03683744⟩
Guanxiong Wang, Lincheng Xu, Eric Serre, Pierre Sagaut. Large temperature difference heat dominated flow simulations using a pressure-based lattice Boltzmann method with mass correction. Physics of Fluids, 2021, 33 (11), pp.116107. ⟨10.1063/5.0073178⟩. ⟨hal-03438869⟩ Plus de détails...
This paper addresses simulation of heat dominated compressible flows in a closed cavity using a pressure-based lattice Boltzmann (LB) method, in which thermal effects are modeled by applying a pressure-featured zero-order moment of distribution functions. A focus is made on the conservation of mass at boundary nodes, which is a challenging issue that significantly complicated by the density-decoupled zero-order moment here. The mass leakage at boundary nodes is mathematically quantified, which enables an efficient local mass correction scheme. The performance of this solver is assessed by simulating buoyancy-driven flows in a closed deferentially heated cavity with large temperature differences (non-Boussinesq) at Rayleigh numbers ranging from 103 to 107. Simulations show that mass leakage at solid walls in such configurations is a critical issue to obtain reliable solutions, and it eventually leads to simulations overflow when the cavity is inclined. The proposed mass correction scheme is, however, shown to be effective to control the mass leakage and get accurate solutions. Thus, associated with the proposed mass conservation scheme, the pressure-based LB method becomes reliable to study natural convection dominated flows at large temperature differences in closed geometries with mesh aligned boundaries or not
Guanxiong Wang, Lincheng Xu, Eric Serre, Pierre Sagaut. Large temperature difference heat dominated flow simulations using a pressure-based lattice Boltzmann method with mass correction. Physics of Fluids, 2021, 33 (11), pp.116107. ⟨10.1063/5.0073178⟩. ⟨hal-03438869⟩
H. Bufferand, J. Bucalossi, G. Ciraolo, G. Falchetto, A. Gallo, et al.. Progress in edge plasma turbulence modelling hierarchy of models from 2D transport application to 3D fluid simulations in realistic tokamak geometry. Nuclear Fusion, 2021, 61 (11), pp.116052. ⟨10.1088/1741-4326/ac2873⟩. ⟨hal-03377162⟩ Plus de détails...
This contribution presents the recent effort at CEA and French federation for Fusion to simulate edge plasma transport with the new code SOLEDGE3X. The latter can be used both as a 2D transport code or as a 3D turbulence code. It makes possible simulating edge plasma up to the first wall including the complex wall geometry. It also includes neutral recycling and impurity sputtering, seeding and transport. In order to improve turbulence description in transport simulation, a reduced model for turbulence intensity prediction has been derived and implemented, based on "kepsilon" like models from the neutral fluid community. Applications to a JET L-mode detached plasma and to a WEST plasma are used as illustration of the code abilities
H. Bufferand, J. Bucalossi, G. Ciraolo, G. Falchetto, A. Gallo, et al.. Progress in edge plasma turbulence modelling hierarchy of models from 2D transport application to 3D fluid simulations in realistic tokamak geometry. Nuclear Fusion, 2021, 61 (11), pp.116052. ⟨10.1088/1741-4326/ac2873⟩. ⟨hal-03377162⟩
S. Baschetti, H. Bufferand, G. Ciraolo, Ph Ghendrih, E. Serre, et al.. Self-consistent cross-field transport model for core and edge plasma transport. Nuclear Fusion, 2021, 61 (10), pp.106020. ⟨10.1088/1741-4326/ac1e60⟩. ⟨hal-03380310⟩ Plus de détails...
A two-equation model to self-consistently determine cross-field fluxes in the edge and scrape-off layer region of diverted plasma is used to complete 2D mean-field edge transport description of plasma wall interaction. Inspired by the Reynolds Average Navier-Stokes simulations for neutral fluids, this model is based on the local evolution of the turbulent kinetic energy κ and its dissipation rate ε. These two equations are algebraically derived for RANS modeling and are very slightly modified and adapted to describe self-consistent plasma turbulent transport. The general features of the model are discussed and bridged to the well-known predatorprey and quasilinear models commonly used to investigate plasma transport. Specific closures are proposed based on the interchange turbulence. Results of the 1D model are confronted to experimental evidence by analyzing the computed SOL width and comparing the results to the existing scaling law for L-mode plasmas. Introducing a dependence on the shear of large scale flows, typically the zonal flows, 1D simulations can exhibit an H-mode like transition when increasing the input power, generating an increased stored energy thanks to an interface barrier located at the separatrix. Further 2D plasma-wall interaction simulations for WEST are analyzed that show a good match with the experimental profiles, as well as a ballooned transport driving turbulent transport in the divertor SOL and nearly no transport in the private flux region. The SOL width of WEST is also recovered. These results show the remarkable capability of the κ-ε model to capture key aspects of the physics of turbulent transport throughout the plasma knowing that a unique scalar free parameter is available to tune cross field transport in the whole 2D cross section of the plasma.
S. Baschetti, H. Bufferand, G. Ciraolo, Ph Ghendrih, E. Serre, et al.. Self-consistent cross-field transport model for core and edge plasma transport. Nuclear Fusion, 2021, 61 (10), pp.106020. ⟨10.1088/1741-4326/ac1e60⟩. ⟨hal-03380310⟩
S. Di Genova, A. Gallo, N. Fedorczak, H. Yang, G. Ciraolo, et al.. Modelling of tungsten contamination and screening in WEST plasma discharges. Nuclear Fusion, 2021, 61 (10), pp.106019. ⟨10.1088/1741-4326/ac2026⟩. ⟨hal-03380329⟩ Plus de détails...
The WEST experiment is currently operating with tungsten plasma-facing components and testing ITER-like divertor monoblocks. In order to support WEST experiments interpretation, numerical analyses were carried out. Starting from WEST experimental data, realistic background plasma conditions were reproduced through SolEdge-EIRENE and used as input for ERO2.0 simulations to investigate tungsten migration. Tungsten contamination due to the different plasma-facing components was modelled under different plasma conditions, highlighting a non-negligible contribution of tungsten coming from the tokamak main chamber. Tungsten penetration factor was computed and used as an indication for tungsten screening by the background plasma at the different tokamak plasma-facing components. Simulations showed the main chamber components to be very weakly screened. Light impurities charge was showed to influence not only tungsten sputtering, but also its probability to enter the confined plasma. Simulations results indicated that even when the tungsten source is not heavily influenced by self-sputtering, contamination of the confined plasma can be strongly impacted by it in low density background plasma conditions. Finally, a one-to-one comparison between tungsten visible spectroscopy at the lower divertor from experimental data and from synthetic diagnostics was performed, showing that it is possible to reproduce a realistic lower divertor signal following experimental evidence on light impurities asymmetry between the targets.
S. Di Genova, A. Gallo, N. Fedorczak, H. Yang, G. Ciraolo, et al.. Modelling of tungsten contamination and screening in WEST plasma discharges. Nuclear Fusion, 2021, 61 (10), pp.106019. ⟨10.1088/1741-4326/ac2026⟩. ⟨hal-03380329⟩
M Raghunathan, Y Marandet, H Bufferand, G Ciraolo, Ph Ghendrih, et al.. Generalized Collisional Fluid Theory for Multi-Component, Multi-Temperature Plasma Using The Linearized Boltzmann Collision Operator for Scrape-Off Layer/Edge Applications. Plasma Physics and Controlled Fusion, 2021, 63 (6), pp.064005. ⟨10.1088/1361-6587/abf670⟩. ⟨hal-03384547⟩ Plus de détails...
M Raghunathan, Y Marandet, H Bufferand, G Ciraolo, Ph Ghendrih, et al.. Generalized Collisional Fluid Theory for Multi-Component, Multi-Temperature Plasma Using The Linearized Boltzmann Collision Operator for Scrape-Off Layer/Edge Applications. Plasma Physics and Controlled Fusion, 2021, 63 (6), pp.064005. ⟨10.1088/1361-6587/abf670⟩. ⟨hal-03384547⟩
E. Laribi, E. Serre, P. Tamain, H. Yang. Impact of negative triangularity on edge plasma transport and turbulence in TOKAM3X simulations. Nuclear Materials and Energy, 2021, pp.101012. ⟨10.1016/j.nme.2021.101012⟩. ⟨hal-03214958⟩ Plus de détails...
The impact of triangularity on edge plasma transport and turbulence is addressed from full 3D turbulence simulations performed with TOKAM3X. Flux driven fluid simulations are run on analytical magnetic equilibria generated with positive and negative triangularity δ in a bottom limiter configuration. The conservation of the energy is assured by the increase of the bottom limiter radial position from δ > 0 to δ < 0. Changing the triangularity impacts both the plasma equilibrium and the turbulence. In particular, negative triangularity leads to a reduction of the density and electron temperature decay lengths in agreement with the literature. Concerning the turbulence, in all the simulations, it remains ballooned with an enhanced level of fluctuations at low field side in comparison to the high field one. Moreover, no clear trend is visible on the relative level of fluctuations of both density and electron temperature in the CFR whereas an enhancement (resp. reduction) is visible in the scrape-off layer at the low field side midplane for the negative (resp. positive) triangularity simulations. This behaviour differs from TCV and DIII-D measurements which show the benefit of negative triangularity in terms of turbulence reduction and increased confinement. However, no conclusion is drawn from our preliminary study concerning the impact of triangularity on the turbulent transport. Change in triangularity impacts many simulation control parameters, as in the experiments, and that the analysis of its impact alone on the dynamics of the plasma is not obvious in this configuration.
E. Laribi, E. Serre, P. Tamain, H. Yang. Impact of negative triangularity on edge plasma transport and turbulence in TOKAM3X simulations. Nuclear Materials and Energy, 2021, pp.101012. ⟨10.1016/j.nme.2021.101012⟩. ⟨hal-03214958⟩
G. Ciraolo, S. Di Genova, H. Yang, A. Gallo, N. Fedorczak, et al.. INTERPRETATIVE MODELING OF IMPURITY TRANSPORT AND TUNGSTEN SOURCES IN WEST BOUNDARY PLASMA. Nuclear Fusion, 2021, 61 (12), pp.126015. ⟨10.1088/1741-4326/ac2439⟩. ⟨hal-03420146⟩ Plus de détails...
The contamination of core plasma by high-Z impurities, especially tungsten (W), is the main reason of very high level of radiated power in WEST experiments. Intrinsic light impurities, mainly oxygen and carbon, play a dominant role in the sputtering of W on plasma facing components. In this contribution, we present a detailed analysis of WEST experiments supported by numerical modeling performed with the transport code SOLEDGE-EIRENE providing a clear picture of light impurities transport and poloidal distribution. Moreover, making use of SOLEDGE-ERO2.0 simulations, possible strategies to reduce core contamination due to W penetration are presented. .
G. Ciraolo, S. Di Genova, H. Yang, A. Gallo, N. Fedorczak, et al.. INTERPRETATIVE MODELING OF IMPURITY TRANSPORT AND TUNGSTEN SOURCES IN WEST BOUNDARY PLASMA. Nuclear Fusion, 2021, 61 (12), pp.126015. ⟨10.1088/1741-4326/ac2439⟩. ⟨hal-03420146⟩
Raffaele Tatali, Eric Serre, Patrick Tamain, Davide Galassi, Philippe Ghendrih, et al.. Impact of collisionality on turbulence in the edge of tokamak plasma using 3D global simulations. Nuclear Fusion, 2021, ⟨10.1088/1741-4326/abe98b⟩. ⟨hal-03182318⟩ Plus de détails...
Collisionality is one of the key parameters in determining turbulent transport in the plasma edge, regulating phenomena such as "shoulder formation", separation of scale lengths in the scrape-off layer, turbulence damping and zonal flow dynamics. Understanding its role is therefore of primary importance for future reactors like ITER. Obtaining reliable predictions and a better characterization of plasma flow properties when varying collisionality remains, however, a critical challenge for the simulations. This paper focuses on the impact of varying collisionality in a nonisothermal three-dimensional fluid model of the plasma edge. A high field side limited configuration encompassing open and closed magnetic field lines with parameters typical of a medium-sized tokamak is considered. The present model can consistently account for the variations of collisionality and its impact on both the parallel resistivity η and the ion and electron parallel thermal conductivities χ e,i. Details on mean flow and turbulence properties are given. Changing collisionality leads to significant changes in the flow properties both on the mean and fluctuating quantities. In particular, lowering collisionality decreases the size of coherent structures, the fluctuation levels of turbulence, and steepens the density and temperature equilibrium profiles around the separatrix leading to a global reduction of the turbulent transport. The scrape-off layer (SOL) width is observed to increase with collisionality, eventually resulting in the disappearance of the scale lengths separation between near and far SOL, consistently with previous experimental observations. At low collisionality, where the presence of narrow feature is well-established, a contribution of heat conduction increases up to compete with heat convection.
Raffaele Tatali, Eric Serre, Patrick Tamain, Davide Galassi, Philippe Ghendrih, et al.. Impact of collisionality on turbulence in the edge of tokamak plasma using 3D global simulations. Nuclear Fusion, 2021, ⟨10.1088/1741-4326/abe98b⟩. ⟨hal-03182318⟩
B D Dudson, W A Gracias, R Jorge, A H Nielsen, J M B Olsen, et al.. Edge turbulence in ISTTOK: a multi-code fluid validation. Plasma Physics and Controlled Fusion, 2021. ⟨hal-03179634⟩ Plus de détails...
B D Dudson, W A Gracias, R Jorge, A H Nielsen, J M B Olsen, et al.. Edge turbulence in ISTTOK: a multi-code fluid validation. Plasma Physics and Controlled Fusion, 2021. ⟨hal-03179634⟩
B Luce, P Tamain, G Ciraolo, Ph Ghendrih, G Giorgiani, et al.. Impact of three-dimensional magnetic perturbations on turbulence in tokamak edge plasmas. Plasma Physics and Controlled Fusion, 2021, ⟨10.1088/1361-6587/abf03f⟩. ⟨hal-03144400⟩ Plus de détails...
The impact of resonant magnetic perturbations (RMP) on the plasma edge equilibrium and on the turbulence is investigated in a circular limited configuration. The study is based on a Braginski-based isothermal fluid model. The flow response of an unperturbed case to a small amplitude three-dimensional single mode RMP is studied and a scan in amplitude and poloidal and toroidal mode number is performed. Special attention is given when magnetic islands appear in the simulation domain on flux surfaces of rational safety factor. Results show an impact of Magnetic Perturbations (MPs) on both the plasma equilibrium and on the turbulence properties, with a deviation to the reference solution which depends on the MPs amplitude and on their wavenumbers. The impact of MPs on turbulence is however globally weaker than on the plasma equilibrium, suggesting a stabilizing effect of the MP on turbulent transport. Experimental trends are recovered such as the density pump-out and the increase of the radial electric field as well as the reorganization of the parallel velocity. The ballooning of the transport is modified under the effect of the perturbations, with a shift of the peaked poloidal region from the upper to the lower outer midplane. In the present model, the SOL width is observed decreasing in the presence of MPs. Turbulence properties are also impacted with the density fluctuations level decreasing in perturbed solutions and the intermittency is globally weakened.
B Luce, P Tamain, G Ciraolo, Ph Ghendrih, G Giorgiani, et al.. Impact of three-dimensional magnetic perturbations on turbulence in tokamak edge plasmas. Plasma Physics and Controlled Fusion, 2021, ⟨10.1088/1361-6587/abf03f⟩. ⟨hal-03144400⟩
G Giorgiani, H. Bufferand, F. Schwander, E. Serre, P. Tamain. A high-order non field-aligned approach for the discretization of strongly anistropic diffusion operators in magnetic fusion. Computer Physics Communications, 2020, 254, pp.107375. ⟨10.1016/j.cpc.2020.107375⟩. ⟨hal-02613709⟩ Plus de détails...
In this work we present a hybrid discontinuous Galerkin scheme for the solution of extremely anisotropic diffusion problems arising in magnetized plasmas for fusion applications. Unstructured meshes, non-aligned with respect to the dominant diffusion direction, allow an unequalled flexibility in discretizing geometries of any shape, but may lead to spurious numerical diffusion. Curved triangles or quadrangles are used to discretize the poloidal plane of the machine, while a structured discretization is used in the toroidal direction. The proper design of the numerical fluxes guarantees the correct convergence order at any anisotropy level. Computations performed on well-designed 2D and 3D numerical tests show that non-aligned discretizations are able to provide spurious diffusion free solutions as long as high-order interpolations are used. Introducing an explicit measure of the numerical diffusion, a careful investigation is carried out showing an exponential increase of this latest with respect to the non-alignment of the mesh with the diffusion direction, as well as an exponential decrease with the polynomial degree of interpolation. A brief assessment of the method with respect to two finite-difference schemes using non-aligned discretization, but classically used in fusion modeling, is also presented.
G Giorgiani, H. Bufferand, F. Schwander, E. Serre, P. Tamain. A high-order non field-aligned approach for the discretization of strongly anistropic diffusion operators in magnetic fusion. Computer Physics Communications, 2020, 254, pp.107375. ⟨10.1016/j.cpc.2020.107375⟩. ⟨hal-02613709⟩
T. Cartier-Michaud, D. Galassi, Ph Ghendrih, P. Tamain, F. Schwander, et al.. A posteriori error estimate in fluid simulations of turbulent edge plasmas for magnetic fusion in tokamak using the data mining iPoPe method. Physics of Plasmas, 2020. ⟨hal-02613800⟩ Plus de détails...
Progressing towards more reliable numerical solutions in the simulation of plasma for magnetic confinement fusion has become a critical issue for the success of the ITER operation. This requires developing rigorous and efficient methods of verification of the numerical simulations in any relevant flow regimes of the operation. The paper introduces a new formulation of the PoPe 1 method, namely the independent Projection on Proper elements method (iPoPe) to quantify the numerical error by performing a data-driven identification of the mathematical model from the simulation outputs. Based on a statistical postprocessing of the outputs database, the method provides a measure of the error by estimating the distance between the (numerical) effective and (analytical) theoretical weights of each operator implemented in the mathematical model. The efficiency of the present method is illustrated on turbulent edge plasma simulations based on a drift-reduced Braginskii fluid model in realistic magnetic geometries. Results show the effective order of the numerical method in these multiscale flow regimes as well as the values of the plasma parameters which can be safely simulated with respect to a given discretization. In this sense, the method goes one step further than the Method of Manufactured Solution (MMS 2-4), recently introduced in fusion, and provides an efficient verification procedure of the numerical simulations in any regimes, including turbulent ones that could be generalized to other scientific domains.
T. Cartier-Michaud, D. Galassi, Ph Ghendrih, P. Tamain, F. Schwander, et al.. A posteriori error estimate in fluid simulations of turbulent edge plasmas for magnetic fusion in tokamak using the data mining iPoPe method. Physics of Plasmas, 2020. ⟨hal-02613800⟩
R. Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios. Nuclear Fusion, 2019, 59 (10), pp.106019. ⟨10.1088/1741-4326/ab3005⟩. ⟨hal-02468022⟩ Plus de détails...
The SOLEDGE-EIRENE edge plasma code provides solutions for particle and energy transport in the plasma edge within complex and realistic 2D geometries (Bufferand et al 2015 Nucl. Fusion 55 053025). In this work, divertor detachment is simulated on HL-2M alternative magnetic configurations in pure deuterium plasma. Starting from a typical HL-2M low single-null configuration, the snowflake plus (SF+) and snowflake minus (SF-) configurations have then been investigated. Detachment of the outer target is studied in these configurations during plasma density ramps controlled by a fueling source, with constant input power and constant radial transport coefficients. Some typical characteristics of detachment, like threshold, depth and upstream window of detachment are investigated. In the three geometries, detachment onset and evolution with upstream plasma density is characterized by the gradual displacement of a radiation front from the outer target to the main X-point, as observed in experiments. It is found that, whatever the detachment in terms of particle, momentum or power dissipation, the detachment threshold is dominated primarily by the geometrical structure of the divertor plate and does not exhibit dependence on the magnetic configuration of the diverted plasma volume. In particular, the parallel connection length in the divertor is not found to affect the detachment threshold, in contrast with simple expectations from the two-point model, but in agreement with experimental findings.
R. Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios. Nuclear Fusion, 2019, 59 (10), pp.106019. ⟨10.1088/1741-4326/ab3005⟩. ⟨hal-02468022⟩
F. Nespoli, P. Tamain, N. Fedorczak, G. Ciraolo, D. Galassi, et al.. 3D structure and dynamics of filaments in turbulence simulations of WEST diverted plasmas. Nuclear Fusion, 2019. ⟨hal-02364554⟩ Plus de détails...
We study the effect of a diverted magnetic geometry on edge plasma turbulence, focusing on the three-dimensional structure and dynamics of filaments, also called blobs, in simulations of the WEST tokamak, featuring a primary and secondary X-point. For this purpose, in addition to classical analysis techniques, we apply here a novel fully 3D Blob Recognition And Tracking (BRAT) algorithm, allowing for the first time to resolve the three-dimensional structure and dynamics of the blobs in a turbulent 3D plasma featuring a realistic magnetic geometry. The results are tested against existing theoretical scalings of blob velocity [Myra et al, Physics of Plasmas 2006]. The complementary analysis of the 3D structure of the filaments shows how they disconnect from the divertor plate in the vicinity of the X-points, leading to a transition from a sheath-connected regime to the ideal-interchange one. Furthermore, the numerical results show non-negligible effects of the turbulent background plasma: approximately half of the detected filaments are involved in mutual interactions, eventually resulting in negative radial velocities, and a fraction of the filaments is generated by turbulence directly below the X-point.
F. Nespoli, P. Tamain, N. Fedorczak, G. Ciraolo, D. Galassi, et al.. 3D structure and dynamics of filaments in turbulence simulations of WEST diverted plasmas. Nuclear Fusion, 2019. ⟨hal-02364554⟩
G. Ciraolo, A. Thin, H. Bufferand, J. Bucalossi, N. Fedorczak, et al.. First modeling of strongly radiating WEST plasmas with SOLEDGE-EIRENE. Nuclear Materials and Energy, 2019, 20, pp.100685. ⟨10.1016/j.nme.2019.100685⟩. ⟨hal-02468035⟩ Plus de détails...
We present first results of SOLEDGE-EIRENE modeling a strongly radiating plasma in the WEST tokamak. Using measurements from a reciprocating Langmuir probe we have determined the SOLEDGE input parameters, i.e. separatrix density at outboard midplane and radial transport coefficients typical of L-mode plasma. We have performed deuterium plasma simulations with presence of oxygen, injected from the core boundary into the simulation domain. The comparison between the radiated power measured from the bolometry in the divertor region and the one computed from SOLEDGE simulations seems to indicate a concentration of oxygen of about 2%. Moreover we have obtained good agreement between simulation results and experimental measurements on electron density and electron temperature profiles at the outer strike point. First qualitative analysis of spectroscopic synthetic diagnostic on D-alpha signals is also presented.
G. Ciraolo, A. Thin, H. Bufferand, J. Bucalossi, N. Fedorczak, et al.. First modeling of strongly radiating WEST plasmas with SOLEDGE-EIRENE. Nuclear Materials and Energy, 2019, 20, pp.100685. ⟨10.1016/j.nme.2019.100685⟩. ⟨hal-02468035⟩
R Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of alternative divertor configuration on plasma detachment: pure Deuterium simulations with SolEdge2D-EIRENE edge transport code for HL-2M scenario. Nuclear Fusion, 2019. ⟨hal-02370418⟩ Plus de détails...
The SOLEDGE-EIRENE edge plasma code provides solutions for particle & energy transport in the plasma edge within complex and realistic 2D geometries [1]. In this work, divertor detachment is simulated on the HL-2M alternative magnetic configurations in pure Deuterium plasma. Starting from typical HL-2M low single-null (SN) configuration, the snowflake plus (SF+) and snowflake minus (SF-) configurations have been investigated. Detachment of the outer target is studied in these configurations during plasma density ramps controlled by a fueling source, at constant input power and constant radial transport coefficients. Some typical characteristics of detachment, like threshold, depth and upstream window of detachment are investigated. In the three geometries, detachment onset and evolution with upstream plasma density is characterized by the gradual displacement of a radiation front from the outer target to the main X-point, as observed in experiments. It is found that, whatever the detachment in terms of particle, momentum or power dissipation, the detachment threshold is dominated primarily by the geometrical structure of divertor plate and it does not exhibit dependence on the magnetic configuration of the diverted plasma volume. In particular, the parallel connection length in the divertor is not found to affect the detachment threshold, in contrast with simple expectations from the 2-point model, but in agreement with experimental findings.
R Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of alternative divertor configuration on plasma detachment: pure Deuterium simulations with SolEdge2D-EIRENE edge transport code for HL-2M scenario. Nuclear Fusion, 2019. ⟨hal-02370418⟩
S. Baschetti, H. Bufferand, G. Ciraolo, N. Fedorczak, P. Ghendrih, et al.. A κ − ε model for plasma anomalous transport in tokamaks: closure via the scaling of the global confinement. Nuclear Materials and Energy, 2019, 19, pp.200-204. ⟨10.1016/j.nme.2019.02.032⟩. ⟨hal-02177039⟩ Plus de détails...
A reduced model for radial anomalous transport of plasma in tokamaks, inspired by the Reynolds-Averaged Navier-Stokes (RANS) approach, is presented assuming diffusion as governing mechanism. In order to self-consistently calculate transport coefficients, an empirical equation is built for the turbulent kinetic energy and the system is closed via the scaling law of global confinement. In such way the SOL width appears to recover experimental dependencies with respect to machine parameters and interestingly, when the model is implemented in a 2D transport code for a realistic study-case, mean fields retrieve some features already observed in 1st-principle turbulent codes.
S. Baschetti, H. Bufferand, G. Ciraolo, N. Fedorczak, P. Ghendrih, et al.. A κ − ε model for plasma anomalous transport in tokamaks: closure via the scaling of the global confinement. Nuclear Materials and Energy, 2019, 19, pp.200-204. ⟨10.1016/j.nme.2019.02.032⟩. ⟨hal-02177039⟩
Julien Denis, J. Bucalossi, G. Ciraolo, Etienne A Hodille, B. Pégourié, et al.. Dynamic modelling of local fuel inventory and desorption in the whole tokamak vacuum vessel for auto-consistent plasma-wall interaction simulations. Nuclear Materials and Energy, 2019, 19, pp.550-557. ⟨10.1016/j.nme.2019.03.019⟩. ⟨hal-02902060⟩ Plus de détails...
An extension of the SolEdge2D-EIRENE code package, named D-WEE, has been developed to add the dynamics of thermal desorption of hydrogen isotopes from the surface of plasma facing materials. To achieve this purpose, D-WEE models hydrogen isotopes implantation, transport and retention in those materials. Before launching auto-consistent simulation (with feedback of D-WEE on SolEdge2D-EIRENE), D-WEE has to be initialised to ensure a realistic wall behaviour in terms of dynamics (pumping or fuelling areas) and fuel content. A methodology based on modelling is introduced to perform such initialisation. A synthetic plasma pulse is built from consecutive SolEdge2D-EIRENE simulations. This synthetic pulse is used as a plasma background for the D-WEE module. A sequence of plasma pulses is simulated with D-WEE to model a tokamak operation. This simulation enables to extract at a desired time during a pulse the local fuel inventory and the local desorption flux density which could be used as initial condition for coupled plasma-wall simulations. To assess the relevance of the dynamic retention behaviour obtained in the simulation, a confrontation to post-pulse experimental pressure measurement is performed. Such confrontation reveals a qualitative agreement between the temporal pressure drop obtained in the simulation and the one observed experimentally. The simulated dynamic retention during the consecutive pulses is also studied.
Julien Denis, J. Bucalossi, G. Ciraolo, Etienne A Hodille, B. Pégourié, et al.. Dynamic modelling of local fuel inventory and desorption in the whole tokamak vacuum vessel for auto-consistent plasma-wall interaction simulations. Nuclear Materials and Energy, 2019, 19, pp.550-557. ⟨10.1016/j.nme.2019.03.019⟩. ⟨hal-02902060⟩
Giorgio Giorgiani, H. Bufferand, G. Ciraolo, Eric Serre, P. Tamain. A magnetic-field independent approach for strongly anisotropic equations arising plasma-edge transport simulations. Nuclear Materials and Energy, 2019, 19, pp.340-345. ⟨10.1016/j.nme.2019.03.002⟩. ⟨hal-02177048⟩ Plus de détails...
A [Summary] The control of the power exhaust in tokamaks is still an open issue for the future fusion operations. The heat loads on divertor and limiter PFCs is largely determined by the physics of the Scrape-Off Layer (SOL), and therefore it depends mainly on the geometry of the magnetic surfaces and on the geometry of wall components. A better characterization of the heat exhaust mechanisms requires therefore to improve the capabilities of the transport codes in terms of geometrical description of the wall components and in terms of the description of the magnetic geometry. The possibility of dealing with evolving magnetic configurations becomes also critical: during start-up or control operations, for example, the evolution of particles and heat fluxes is little known, although being critical for the safety of the machine. Hence, among the new capabilities of future transport codes will be the possibility of accurately describe the reactor chamber, and the flexibility with respect the magnetic configuration. In particular, avoiding expensive re-meshing of the computational domain in case of evolving equilibrium is mandatory. In order to fulfill these requirements, in this work a fluid solver based on non-aligned discretization is used to solve the plasma-edge transport equations for density, momentum and energies. Preliminary tests on non-structured meshes and realistic geometries/physical parameters show the pertinency of this novel approach.
Giorgio Giorgiani, H. Bufferand, G. Ciraolo, Eric Serre, P. Tamain. A magnetic-field independent approach for strongly anisotropic equations arising plasma-edge transport simulations. Nuclear Materials and Energy, 2019, 19, pp.340-345. ⟨10.1016/j.nme.2019.03.002⟩. ⟨hal-02177048⟩
Davide Galassi, Guido Ciraolo, Patrick Tamain, Hugo Bufferand, Philippe Ghendrih, et al.. Tokamak edge plasma turbulence interaction with magnetic X-point in 3D global simulations. Fluids, 2019, 4 (1), pp.50. ⟨10.3390/fluids4010050⟩. ⟨hal-02176982⟩ Plus de détails...
Turbulence in the edge plasma of a tokamak is a key actor in the determination of the confinement properties. The divertor configuration seems to be beneficial for confinement, suggesting an effect on turbulence of the particular magnetic geometry introduced by the X-point. Simulations with the 3D fluid turbulence code TOKAM3X are performed here to evaluate the impact of a diverted configuration on turbulence in the edge plasma, in an isothermal framework. The presence of the X-point is found, locally, to affect both the shape of turbulent structures and the amplitude of fluctuations, in qualitative agreement with recent experimental observations. In particular, a quiescent region is found in the divertor scrape-off layer (SOL), close to the separatrix. Globally, a mild transport barrier spontaneously forms in the closed flux surfaces region near the separatrix, differently from simulations in limiter configuration. The effect of turbulence-driven Reynolds stress on the formation of the barrier is found to be weak by dedicated simulations, while turbulence damping around the X-point seems to globally reduce turbulent transport on the whole flux surface. The magnetic shear is thus pointed out as a possible element that contributes to the formation of edge transport barriers.
Davide Galassi, Guido Ciraolo, Patrick Tamain, Hugo Bufferand, Philippe Ghendrih, et al.. Tokamak edge plasma turbulence interaction with magnetic X-point in 3D global simulations. Fluids, 2019, 4 (1), pp.50. ⟨10.3390/fluids4010050⟩. ⟨hal-02176982⟩
Davide Galassi, Guido Ciraolo, Patrick Tamain, Hugo Bufferand, Philippe Ghendrih, et al.. Tokamak Edge Plasma Turbulence Interaction with Magnetic X-Point in 3D Global Simulations. Fluids, 2019, 4 (1), pp.50. ⟨10.3390/fluids4010050⟩. ⟨hal-02176982⟩ Plus de détails...
Turbulence in the edge plasma of a tokamak is a key actor in the determination of the confinement properties. The divertor configuration seems to be beneficial for confinement, suggesting an effect on turbulence of the particular magnetic geometry introduced by the X-point. Simulations with the 3D fluid turbulence code TOKAM3X are performed here to evaluate the impact of a diverted configuration on turbulence in the edge plasma, in an isothermal framework. The presence of the X-point is found, locally, to affect both the shape of turbulent structures and the amplitude of fluctuations, in qualitative agreement with recent experimental observations. In particular, a quiescent region is found in the divertor scrape-off layer (SOL), close to the separatrix. Globally, a mild transport barrier spontaneously forms in the closed flux surfaces region near the separatrix, differently from simulations in limiter configuration. The effect of turbulence-driven Reynolds stress on the formation of the barrier is found to be weak by dedicated simulations, while turbulence damping around the X-point seems to globally reduce turbulent transport on the whole flux surface. The magnetic shear is thus pointed out as a possible element that contributes to the formation of edge transport barriers.
Davide Galassi, Guido Ciraolo, Patrick Tamain, Hugo Bufferand, Philippe Ghendrih, et al.. Tokamak Edge Plasma Turbulence Interaction with Magnetic X-Point in 3D Global Simulations. Fluids, 2019, 4 (1), pp.50. ⟨10.3390/fluids4010050⟩. ⟨hal-02176982⟩
Marco Martins Afonso, Philippe Meliga, Eric Serre. Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step. Fluids, 2019, 4 (1), pp.33. ⟨10.3390/fluids4010033⟩. ⟨hal-02176963⟩ Plus de détails...
With the aim of providing a first step in the quest for a reduction of the aerodynamic drag on the rear-end of a car, we study the phenomena of separation and reattachment of an incompressible flow by focusing on a specific aerodynamic geometry, namely a backward-slanted step at 25 circle of inclination. The ensuing recirculation bubble provides the basis for an analytical and numerical investigation of streamwise-streak generation, lift-up effect, and turbulent-wake and Kelvin-Helmholtz instabilities. A linear stability analysis is performed, and an optimal control problem with a steady volumic forcing is tackled by means of a variational formulation, adjoint methods, penalization schemes, and an orthogonalization algorithm. Dealing with the transient growth of spanwise-periodic perturbations, and inspired by the need of physically-realizable disturbances, we finally provide a procedure attaining a kinetic-energy maximal gain on the order of 106, with respect to the power introduced by the external forcing.
Marco Martins Afonso, Philippe Meliga, Eric Serre. Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step. Fluids, 2019, 4 (1), pp.33. ⟨10.3390/fluids4010033⟩. ⟨hal-02176963⟩
J. Soler, F. Schwander, G Giorgiani, J Liandrat, P Tamain, et al.. A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain. Journal of Computational Physics, 2019, ⟨10.1016/j.jcp.2019.109093⟩. ⟨hal-02477007⟩ Plus de détails...
Highly anisotropic elliptic problems occur in many physical models that need to be solved numerically. A direction of dominant diffusion is thus introduced (called here parallel direction) along which the diffusion coefficient is several orders larger of magnitude than in the perpendicular one. In this case, finite-difference methods based on misaligned stencils are generally not designed to provide an optimal discretization, and may lead the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. This paper proposes an original scheme using non-aligned Cartesian grids and interpolations aligned along a parallel diffusion direction. Here, this direction is assumed to be supported by a divergence-free vector field which never vanishesand it is supposed to be stationary in time. Based on the Support Operator Method (SOM), the self-adjointness property of the parallel diffusion operator is maintained on the discrete level. Compared with existing methods, the present formulation further guarantees the conservativity of the fluxes in both parallel and perpendicular directions. In addition, when the flow intercepts a boundary in the parallel direction, an accurate discretization of the boundary condition is presented that avoids the uncertainties of extrapolated far ghost points classicaly used and ensures a better accuracy of the solution. Numerical tests based on manufactured solutions show the method is able to provide accurate and stable numerical approximations in both periodic and bounded domains with a drastically reduced number of degrees of freedom with respect to non-aligned approaches.
J. Soler, F. Schwander, G Giorgiani, J Liandrat, P Tamain, et al.. A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain. Journal of Computational Physics, 2019, ⟨10.1016/j.jcp.2019.109093⟩. ⟨hal-02477007⟩
H. Bufferand, P. Tamain, S. Baschetti, J. Bucalossi, G. Ciraolo, et al.. Three-dimensional modelling of edge multi-component plasma taking into account realistic wall geometry. Nuclear Materials and Energy, 2019, 18, pp.82-86. ⟨10.1016/j.nme.2018.11.025⟩. ⟨hal-02176521⟩ Plus de détails...
H. Bufferand, P. Tamain, S. Baschetti, J. Bucalossi, G. Ciraolo, et al.. Three-dimensional modelling of edge multi-component plasma taking into account realistic wall geometry. Nuclear Materials and Energy, 2019, 18, pp.82-86. ⟨10.1016/j.nme.2018.11.025⟩. ⟨hal-02176521⟩
F. Nespoli, H. Bufferand, M. Valentinuzzi, N. Fedorczak, G. Ciraolo, et al.. Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma. Nuclear Materials and Energy, 2019, 18, pp.29-34. ⟨10.1016/j.nme.2018.11.026⟩. ⟨hal-02176505⟩ Plus de détails...
The edge and scrape-off layer (SOL) plasma of the inter-ELM phase of an H-mode discharge from the TCV tokamak is modeled with the transport code SolEdge2D-EIRENE (Bufferand et al. Nuclear Fusion 55 (2015)). The numerical simulations, in presence and in absence of C impurities sputtered from the first wall, are presented and compared with the experiments, finding an overall good agreement. The application of the standard two-point model to the simulation results leads to an apparent momentum gain along the divertor leg. A two-fluid two-point model featuring thermally decoupled ions and electrons is introduced and applied to the simulation results, overcoming this apparent discrepancy.
F. Nespoli, H. Bufferand, M. Valentinuzzi, N. Fedorczak, G. Ciraolo, et al.. Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma. Nuclear Materials and Energy, 2019, 18, pp.29-34. ⟨10.1016/j.nme.2018.11.026⟩. ⟨hal-02176505⟩
D.M. Fan, Y. Marandet, P. Tamain, H. Bufferand, G. Ciraolo, et al.. Effect of turbulent fluctuations on neutral particles transport with the TOKAM3X-EIRENE turbulence code. Nuclear Materials and Energy, 2019, 18, pp.105-110. ⟨10.1016/j.nme.2018.12.011⟩. ⟨hal-02176529⟩ Plus de détails...
The effect of turbulent fluctuations on the transport of neutral particles (atoms, molecules) in tokamak plasmas is investigated with the 3D global turbulence code TOKAM3X-EIRENE in limiter geometry. The statistical properties of turbulent fields relevant to this work are discussed, including the recycling flux. The neutral particle transport is recalculated on the mean field plasma, and compared to the mean neutral particle density/flows obtained from the turbulent simulation, so as to assess the effects of the fluctuations, in particular on the ionization balance. The latter effects are remarkably modest in the simulation presented here, but are expected to become more and more pronounced as the high recycling regime is approached, in particular because the plasma temperature becomes low enough so that ionization is strongly non-linear. However, the turbulent fluctuations in the SOL do have a substantial effect on the neutral densities on the low field side of the limiter, including in the confined plasma. These effects are traced back to non-linearities in the plasma flux at the wall, and the fluctuations in the latter are identified as an important contributor both to neutral particle density fluctuations and to deviations from mean neutral particle density/flows in the turbulent simulation with respect to the same quantities recalculated on the mean plasma fields.
D.M. Fan, Y. Marandet, P. Tamain, H. Bufferand, G. Ciraolo, et al.. Effect of turbulent fluctuations on neutral particles transport with the TOKAM3X-EIRENE turbulence code. Nuclear Materials and Energy, 2019, 18, pp.105-110. ⟨10.1016/j.nme.2018.12.011⟩. ⟨hal-02176529⟩
Giorgio Giorgiani, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Frédéric Schwander, et al.. A hybrid discontinuous Galerkin method for tokamak edge plasma simulations in global realistic geometry. Journal of Computational Physics, 2018, 374, pp.515-532. ⟨10.1016/j.jcp.2018.07.028⟩. ⟨hal-02114246⟩ Plus de détails...
Progressing toward more accurate and more efficient numerical codes forthe simulation of transport and turbulence in the edge plasma of tokamaks,we propose in this work a new hybrid discontinous Galerkin solver. Basedon 2D advection-diffusion conservation equations for the ion density and theparticle flux in the direction parallel to the magnetic field, the code simulatesplasma transport in the poloidal section of tokamaks, including the open fieldlines of the Scrape-off Layer (SOL) and the closed field lines of the core re-gion. The spatial discretization is based on a high-order hybrid DG schemeon unstructured meshes, which provides an arbitrary high-order accuracywhile reducing considerably the number of coupled degrees of freedom witha local condensation process. A discontinuity sensor is employed to identifycritical elements and regularize the solution with the introduction of artificialdiffusion. Based on a finite-element discretization, not constrained by a flux-aligned mesh, the code is able to describe plasma facing components of anycomplex shape using Bohm boundary conditions and to simulate the plasmain versatile magnetic equilibria, possibly extended up to the center. Nu-merical tests using a manufacturated solution show appropriate convergenceorders when varying independently the number of elements or the degree ofinterpolation. Validation is performed by benchmarking the code with thewell-referenced edge transport code SOLEDGE2D (Bufferandet al.2013,2015 [1, 2]) in the WEST geometry. Final numerical experiments show thecapacity of the code to deal with low-diffusion solutions.
Giorgio Giorgiani, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Frédéric Schwander, et al.. A hybrid discontinuous Galerkin method for tokamak edge plasma simulations in global realistic geometry. Journal of Computational Physics, 2018, 374, pp.515-532. ⟨10.1016/j.jcp.2018.07.028⟩. ⟨hal-02114246⟩
Philippe Ghendrih, Y. Asahi, E. Caschera, Guilhem Dif-Pradalier, P. Peter Donnel, et al.. Generation and dynamics of SOL corrugated profiles. Journal of Physics: Conference Series, 2018, 1125, pp.012011. ⟨10.1088/1742-6596/1125/1/012011⟩. ⟨hal-02196677⟩ Plus de détails...
The staircase transport regime reported in kinetic simulations of plasma turbulent transport in magnetic confinement is recovered with a simple 2D fluid model allowing for reduced damping of the zonal flows. Some of the complex dynamics of the kinetic zonation regime are recovered but the pattern of the corrugation appears to be sinusoidal with a characteristic scale comparable to that of turbulence modes with largest spectral energy, in contrast to regimes observed in global and flux-driven kinetic simulations. Enhanced zonal flows govern both an overall reduction of the SOL width and a gradual steepening of the gradients with distance to the separatrix.
Philippe Ghendrih, Y. Asahi, E. Caschera, Guilhem Dif-Pradalier, P. Peter Donnel, et al.. Generation and dynamics of SOL corrugated profiles. Journal of Physics: Conference Series, 2018, 1125, pp.012011. ⟨10.1088/1742-6596/1125/1/012011⟩. ⟨hal-02196677⟩
Eunok Yim, J.-M. Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor–stator cavity. Journal of Fluid Mechanics, 2018, 848, pp.631 - 647. ⟨10.1017/jfm.2018.239⟩. ⟨hal-02116221⟩ Plus de détails...
The transition to turbulence in the rotating disk boundary layer is investigated in a closed cylindrical rotor-stator cavity via direct numerical simulation (DNS) and linear stability analysis (LSA). The mean flow in the rotor boundary layer is qualitatively similar to the von Karman self-similarity solution. The mean velocity profiles, however, slightly depart from theory as the rotor edge is approached. Shear and centrifugal effects lead to a locally more unstable mean flow than the self-similarity solution, which acts as a strong source of perturbations. Fluctuations start rising there, as the Reynolds number is increased, eventually leading to an edge-driven global mode, characterized by spiral arms rotating counter-clockwise with respect to the rotor. At larger Reynolds numbers, fluctuations form a steep front, no longer driven by the edge, and followed downstream by a saturated spiral wave, eventually leading to incipient turbulence. Numerical results show that this front results from the superposition of several elephant front-forming global modes, corresponding to unstable azimuthal wavenumbers m, in the range m is an element of [32, 78 ]. The spatial growth along the radial direction of the energy of these fluctuations is quantitatively similar to that observed experimentally. This superposition of elephant modes could thus provide an explanation for the discrepancy observed in the single disk configuration, between the corresponding spatial growth rates values measured by experiments on the one hand, and predicted by LSA and DNS performed in an azimuthal sector, on the other hand.
Eunok Yim, J.-M. Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor–stator cavity. Journal of Fluid Mechanics, 2018, 848, pp.631 - 647. ⟨10.1017/jfm.2018.239⟩. ⟨hal-02116221⟩
L Valade, A. Ekedahl, P Ghendrih, Y. Sarazin, Y. Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02196679⟩ Plus de détails...
Hot spot generation by Lower Hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D-1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function with an island structure in the suprathermal part at the phase velocity of the external electrostatic drive. The non-linear features enhance the plasma response driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function with extent up to one thermal velocity is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of 1
L Valade, A. Ekedahl, P Ghendrih, Y. Sarazin, Y. Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02196679⟩
Laurent Valade, Annika Ekedahl, Philippe Ghendrih, Yanick Sarazin, Yuuichi Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02116142⟩ Plus de détails...
Hotspot generation by lower-hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D-1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function. An island structure is formed in the suprathermal part at the phase velocity of the external electrostatic drive. The non-linear features enhance the plasma response, driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function, with extent reaching one thermal velocity, is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of the small-scale features generated by the LH launchers, which are responsible for the interaction with the cold electrons. This mechanism can trigger hotspot generation further in the scrape-off layer than otherwise expected.
Laurent Valade, Annika Ekedahl, Philippe Ghendrih, Yanick Sarazin, Yuuichi Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02116142⟩
Guido Ciraolo, Hugo Bufferand, Pierfrancesco Di Cintio, Philippe Ghendrih, Stefano Lepri, et al.. Fluid and kinetic modelling for non-local heat transport in magnetic fusion devices. Contributions to Plasma Physics, 2018, 58 (6-8), pp.457-464. ⟨10.1002/ctpp.201700222⟩. ⟨hal-02113953⟩ Plus de détails...
In order to improve the presently used ad hoc flux limiter treatment of parallel heat flux transport in edge plasma fluid codes, here, we consider a generalized version of the Fourier law implementing a non-local kernel for the heat flux computation. The Bohm boundary condition at the wall is recovered, introducing a volumetric loss term representing the contribution of suprathermal particles to the energy out flux. As expected, this contribution is negligible in the strongly collisional regime, while it becomes more and more dominant for marginally and low-collisional regimes. In the second part of the paper, we consider a kinetic approach where collisions are considered using the multi-particle collision algorithm. Kinetic simulation results at medium and low collisionality are also reported.
Guido Ciraolo, Hugo Bufferand, Pierfrancesco Di Cintio, Philippe Ghendrih, Stefano Lepri, et al.. Fluid and kinetic modelling for non-local heat transport in magnetic fusion devices. Contributions to Plasma Physics, 2018, 58 (6-8), pp.457-464. ⟨10.1002/ctpp.201700222⟩. ⟨hal-02113953⟩
Serafina Baschetti, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Optimization of turbulence reduced model free parameters based on L-mode experiments and 2D transport simulations. Contributions to Plasma Physics, 2018, 58 (6-8), pp.511-517. ⟨10.1002/ctpp.201700163⟩. ⟨hal-02111708⟩ Plus de détails...
In this paper, a κ−ϵ transport model is presented as a turbulence reduction tool for a typical ohmic L‐mode discharge plasma in a divertor‐configurated tokamak. Taking a Tokamak à configuration variable (TCV) study case, a feedback loop procedure is performed using the SolEdge2D code to acquire plasma diffusivity at the outer mid‐plane. The κ−ϵ model is calibrated through its free parameters with the aim of recovering the diffusivity calculated in the feedback procedure. Finally, it is shown that the model can self‐consistently calculate diffusivity in the whole domain, recovering the poloidal asymmetries due to interchange instabilities.
Serafina Baschetti, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Optimization of turbulence reduced model free parameters based on L-mode experiments and 2D transport simulations. Contributions to Plasma Physics, 2018, 58 (6-8), pp.511-517. ⟨10.1002/ctpp.201700163⟩. ⟨hal-02111708⟩
Dongmei Fan, Yannick Marandet, Patrick Tamain, Hugo Bufferand, Guido Ciraolo, et al.. Self-consistent coupling of the three-dimensional fluid turbulence code TOKAM3X and the kinetic neutrals code EIRENE. Contributions to Plasma Physics, 2018, 58 (6-8), pp.490-496. ⟨10.1002/ctpp.201700216⟩. ⟨hal-02114027⟩ Plus de détails...
The three-dimensional (3D) turbulence code TOKAM3X-EIRENE, coupling the 3D non-isothermal version of TOKAM3X to the EIRENE Monte Carlo solver has been developed with the ability to simulate self-consistently the interactions between large-scale flows and turbulence both in limited and diverted plasmas, including recycling. This is especially important for diverted plasmas, where neutrals play a key role and where the recycling source is strongly dominant. The code package relies on the same interface as the Soledge2D-EIRENE code, which retains state-of-the-art plasma-wall interaction, as well as atomic and molecular physics. In this paper, we present the first results obtained in WEST divertor geometry, in laminar mode, with the aim of verifying the new code package. The divertor density regimes are recovered, and the code results are shown to be consistent with the results of the two-point model, thus opening the way for turbulent simulations.
Dongmei Fan, Yannick Marandet, Patrick Tamain, Hugo Bufferand, Guido Ciraolo, et al.. Self-consistent coupling of the three-dimensional fluid turbulence code TOKAM3X and the kinetic neutrals code EIRENE. Contributions to Plasma Physics, 2018, 58 (6-8), pp.490-496. ⟨10.1002/ctpp.201700216⟩. ⟨hal-02114027⟩
Matteo Valentinuzzi, Giorgio Giorgiani, Yannick Marandet, Hugo Bufferand, Guido Ciraolo, et al.. Fluid description of neutral particles in divertor regimes in WEST. Contributions to Plasma Physics, 2018, 58 (6-8), pp.710-717. ⟨10.1002/ctpp.201700211⟩. ⟨hal-02116176⟩ Plus de détails...
A new neutral fluid code has been developed as a necessary step towards a hybrid fluid/kinetic neutral model, to be used in ITER or DEMO simulations, where part of the divertor will be very collisional for neutrals. The neutral fluid code, which is able to handle complex geometries in view of the coupling to Soledge2D, is tested on plasma backgrounds obtained by Soledge2D‐Eirene in WEST geometry, for different divertor regimes, and is found to be in fair agreement with the kinetic Monte Carlo solver Eirene. The differences are due to the simplifications introduced in the fluid model and to the fact that a fluid description is not fully valid in these cases.
Matteo Valentinuzzi, Giorgio Giorgiani, Yannick Marandet, Hugo Bufferand, Guido Ciraolo, et al.. Fluid description of neutral particles in divertor regimes in WEST. Contributions to Plasma Physics, 2018, 58 (6-8), pp.710-717. ⟨10.1002/ctpp.201700211⟩. ⟨hal-02116176⟩
Hugo Bufferand, Guido Ciraolo, Pierfrancesco Di Cintio, Nicolas Fedorczak, Philippe Ghendrih, et al.. Non-local heat flux application for scrape-off layer plasma. Contributions to Plasma Physics, 2018, 58 (6-8), pp.563-569. ⟨10.1002/ctpp.201700162⟩. ⟨hal-02112673⟩ Plus de détails...
The non-local expression proposed by Luciani-Mora-Virmont is implemented in a one dimensional fluid model for the scrape-off layer. Analytical solutions for heat equation are discussed as well as the impact of sheath boundary conditions on the continuity of the temperature profile. The non-local heat flux is compared to the Spitzer-Härm heat flux for different collisionality. KEYWORDS heat conduction, non-local transport, plasma physics 1 INTRODUCTION At the entrance of the scrape-off layer, the plasma collisionality í µí¼ ⋆ defined as the ratio between the field line length and collision mean free path is found to be of order unity. Despite this low collisionality, the tokamak edge plasma modelling relies mostly on the fluid approach and collisional closures that are theoretically only valid at high collisionality. Departure between Braginskii fluid description and kinetic modelling has been highlighted, particularly an underestimation of temperature gradient by the fluid approach. [1] Several kinetic corrections have been proposed to improve the plasma description at intermediate collisionality. [2-5] In this contribution, we investigate kinetic corrections to the local Spitzer-Härm (Braginskii) closure for the heat flux; more precisely, we focus on applying the non-local expression for the heat flux proposed by Luciani-Mora-Virmont [6] to scrape-off layer physics. In particular, we adapt boundary conditions and implement the non-local expression into a 1D hydrodynamic model for the scrape-off layer.
Hugo Bufferand, Guido Ciraolo, Pierfrancesco Di Cintio, Nicolas Fedorczak, Philippe Ghendrih, et al.. Non-local heat flux application for scrape-off layer plasma. Contributions to Plasma Physics, 2018, 58 (6-8), pp.563-569. ⟨10.1002/ctpp.201700162⟩. ⟨hal-02112673⟩
Nicolas Nace, Patrick Tamain, Camille Baudoin, Hugo Bufferand, Guido Ciraolo, et al.. Impact of safety factor and magnetic shear profiles on edge turbulence in circular limited geometry. Contributions to Plasma Physics, 2018, 58 (6-8), pp.497-504. ⟨10.1002/ctpp.201700174⟩. ⟨hal-02115405⟩ Plus de détails...
The impact of magnetic configuration on edge turbulence properties in circular limiter geometry is investigated using TOKAM3X, a three-dimensional (3D), first-principle, fluid code for edge plasma. The theoretical spatial tilting of magnetic shear on turbulence fluctuations is recovered. Magnetic shear is found to generate or enhance poloidal high/low field sides (HFS/LFS) and up/down asymmetries. A simulation mimicking the impact of an X-point on circular limiter geometry leads to the formation of two transport barriers that are stable in time, thus leading to the improvement of core particle confinement and to reduction of radial turbulent transport. The magnetic shear, which also strongly enhances the E × B shear, is responsible for the barrier formation.
Nicolas Nace, Patrick Tamain, Camille Baudoin, Hugo Bufferand, Guido Ciraolo, et al.. Impact of safety factor and magnetic shear profiles on edge turbulence in circular limited geometry. Contributions to Plasma Physics, 2018, 58 (6-8), pp.497-504. ⟨10.1002/ctpp.201700174⟩. ⟨hal-02115405⟩
Eunok Yim, J.-M Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, 2018, 836, pp.43-71. ⟨10.1017/jfm.2017.771⟩. ⟨hal-02121890⟩ Plus de détails...
This paper proposes a resolution to the conundrum of the roles of convective and absolute instability in transition of the rotating-disk boundary layer. It also draws some comparison with swept-wing flows. Direct numerical simulations based on the incompressible Navier–Stokes equations of the flow over the surface of a rotating disk with modelled roughness elements are presented. The rotating-disk flow has been of particular interest for stability and transition research since the work by Lingwood (J. Fluid Mech., vol. 299, 1995, pp. 17–33) where an absolute instability was found. Here stationary disturbances develop from roughness elements on the disk and are followed from the linear stage, growing to saturation and finally transitioning to turbulence. Several simulations are presented with varying disturbance amplitudes. The lowest amplitude corresponds approximately to the experiment by Imayama et al. (J. Fluid Mech., vol. 745, 2014a, pp. 132–163). For all cases, the primary instability was found to be convectively unstable, and secondary modes were found to be triggered spontaneously while the flow was developing. The secondary modes further stayed within the domain, and an explanation for this is a proposed globally unstable secondary instability. For the low-amplitude roughness cases, the disturbances propagate beyond the threshold for secondary global instability before becoming turbulent, and for the high-amplitude roughness cases the transition scenario gives a turbulent flow directly at the critical Reynolds number for the secondary global instability. These results correspond to the theory of Pier (J. Engng Maths, vol. 57, 2007, pp. 237–251) predicting a secondary absolute instability. In our simulations, high temporal frequencies were found to grow with a large amplification rate where the secondary global instability occurred. For smaller radial positions, low-frequency secondary instabilities were observed, tripped by the global instability. The transition to turbulence in the rotating disk boundary layer is investigated in a closed cylindrical rotor-stator cavity via direct numerical simulation (DNS) and linear stability analysis (LSA). The mean flow in the rotor boundary layer is qualitatively similar to the von Kármán self-similarity solution. The mean velocity profiles, however, slightly depart from theory as the rotor edge is approached. Shear and centrifugal effects lead to a locally more unstable mean flow than the self-similarity solution, which acts as a strong source of perturbations. Fluctuations start rising there, as the Reynolds number is increased, eventually leading to an edge-driven global mode, characterized by spiral arms rotating counterclockwise with respect to the rotor. At larger Reynolds numbers, fluctuations form a steep front, no longer driven by the edge, and followed downstream by a saturated spiral wave, eventually leading to incipient turbulence. Numerical results show that this front results from the superposition of several elephant front-forming global modes, corresponding to unstable azimuthal wavenumbers m, in the range m ∈ [32, 78]. The spatial growth along the radial direction of the energy of these fluctuations is quantitatively similar to that observed experimentally. This superposition of elephant modes could thus provide an explanation for the discrepancy observed in the single disk configuration, between the corresponding spatial growth rates values measured by experiments on the one hand, and predicted by LSA and DNS performed in an azimuthal sector, on the other hand.
Eunok Yim, J.-M Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, 2018, 836, pp.43-71. ⟨10.1017/jfm.2017.771⟩. ⟨hal-02121890⟩
Eunok Yim, J.-M Chomaz, D Martinand, E Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, 2018. ⟨hal-02927579⟩ Plus de détails...
The transition to turbulence in the rotating disk boundary layer is investigated in a closed cylindrical rotor-stator cavity via direct numerical simulation (DNS) and linear stability analysis (LSA). The mean flow in the rotor boundary layer is qualitatively similar to the von Kármán self-similarity solution. The mean velocity profiles, however, slightly depart from theory as the rotor edge is approached. Shear and centrifugal effects lead to a locally more unstable mean flow than the self-similarity solution, which acts as a strong source of perturbations. Fluctuations start rising there, as the Reynolds number is increased, eventually leading to an edge-driven global mode, characterized by spiral arms rotating counterclockwise with respect to the rotor. At larger Reynolds numbers, fluctuations form a steep front, no longer driven by the edge, and followed downstream by a saturated spiral wave, eventually leading to incipient turbulence. Numerical results show that this front results from the superposition of several elephant front-forming global modes, corresponding to unstable azimuthal wavenumbers m, in the range m ∈ [32, 78]. The spatial growth along the radial direction of the energy of these fluctuations is quantitatively similar to that observed experimentally. This superposition of elephant-modes could thus provide an explanation for the discrepancy observed in the single disk configuration, between the corresponding spatial growth rates values measured by experiments on the one hand, and predicted by LSA and DNS performed in an azimuthal sector, on the other hand.
Eunok Yim, J.-M Chomaz, D Martinand, E Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, 2018. ⟨hal-02927579⟩
Giorgio Giorgiani, Hervé Guillard, Boniface Nkonga, Eric Serre. A stabilized Powell–Sabin finite-element method for the 2D Euler equations in supersonic regime. Computer Methods in Applied Mechanics and Engineering, 2018, 340, pp.216-235. ⟨10.1016/j.cma.2018.05.032⟩. ⟨hal-01865708⟩ Plus de détails...
In this paper a Powell–Sabin finite-element (PS-FEM) scheme is presented for the solution of the 2D Euler equations in supersonic regime. The spatial discretization is based on PS splines, that are piecewise quadratic polynomials with a global continuity, defined on conforming triangulations. Some geometrical issues related to the practical construction of the PS elements are discussed, in particular, the generation of the control triangles and the imposition of the boundary conditions. A stabilized formulation is considered, and a novel shock-capturing technique in the context of continuous finite-elements is proposed to reduce oscillations around the discontinuity, and compared with the classical technique proposed by Tezduyar and Senga (2006). The code is verified using manufactured solutions and validated using two challenging numerical examples, which allows to evaluate the performance of the PS discretization in capturing the shocks.
Giorgio Giorgiani, Hervé Guillard, Boniface Nkonga, Eric Serre. A stabilized Powell–Sabin finite-element method for the 2D Euler equations in supersonic regime. Computer Methods in Applied Mechanics and Engineering, 2018, 340, pp.216-235. ⟨10.1016/j.cma.2018.05.032⟩. ⟨hal-01865708⟩
Journal: Computer Methods in Applied Mechanics and Engineering
Dominique Morvan. Comprendre et prévenir les feux de végétation. Université Grenoble Alpes. Encyclopédie de l’Environnement, , 2018. ⟨hal-01678486⟩ Plus de détails...
L’amélioration des politiques de prévention et de réduction du risque incendie en milieu naturel et dans les zones périurbaines nécessite une compréhension approfondie des facteurs qui vont contribuer à l’ignition d’un premier foyer puis à sa propagation sous la forme d’un front de flamme. La dynamique d’un incendie et son impact sur un environnement donné dépendent de différents paramètres, tels que la structure de la strate combustible (herbe, arbustes, arbres), les facteurs de stress auxquels est soumise la végétation (teneur en eau, humidité relative et température de l’air ambiant, vent, pente du terrain), la nature exacte de l’espace impacté (savane, maquis, forêt, zone péri-urbaine). On sait déjà que la puissance maximale atteinte par certains feux dépasse très largement les limites d’efficacité des moyens de lutte les plus puissants (hélicoptères, bombardiers à eau). C’est pour cette raison que les services de lutte, un peu partout dans le monde, ont mis en place depuis de nombreuses années une stratégie basée sur l’attaque précoce des feux naissants. L’efficacité de cette approche semble à présent atteindre ses limites, elle commence même à produire des effets négatifs. En effet, l’élimination systématique des feux de faible intensité a pour première conséquence de favoriser l’accumulation de biomasse au sol et par ce biais d’aggraver un facteur de risque important.
Dominique Morvan. Comprendre et prévenir les feux de végétation. Université Grenoble Alpes. Encyclopédie de l’Environnement, , 2018. ⟨hal-01678486⟩
H. Riahi, Marcello Meldi, Julien Favier, Eric Serre, Eric Goncalves da Silva. A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows. Journal of Computational Physics, 2018, 374, pp.361-383. ⟨10.1016/j.jcp.2018.07.033⟩. ⟨hal-01859760⟩ Plus de détails...
The development of an improved new IBM method is proposed in the present article. This method roots in efficient proposals developed for the simulation of incompressible flows, and it is expanded for compressible configurations. The main feature of this model is the integration of a pressure-based correction of the IBM forcing which is analytically derived from the set of dynamic equations. The resulting IBM method has been integrated in various flow solvers available in the CFD platform OpenFOAM. A rigorous validation has been performed considering different test cases of increasing complexity. The results have been compared with a large number of references available in the literature of experimental and numerical nature. This analysis highlights numerous favorable characteristics of the IBM method, such as precision, flexibility and computational cost efficiency.
H. Riahi, Marcello Meldi, Julien Favier, Eric Serre, Eric Goncalves da Silva. A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows. Journal of Computational Physics, 2018, 374, pp.361-383. ⟨10.1016/j.jcp.2018.07.033⟩. ⟨hal-01859760⟩
Thomas Cartier-Michaud, Philippe Ghendrih, Guilhem Dif-Pradalier, Xavier Garbet, Virginie Grandgirard, et al.. Verification of turbulent simulations using PoPe: quantifying model precision and numerical error with data mining of simulation output. Journal of Physics: Conference Series, 2018, 1125, pp.012005. ⟨10.1088/1742-6596/1125/1/012005⟩. ⟨hal-02196674⟩ Plus de détails...
Verification of a 1D-1V kinetic code with the PoPe method [1] is presented. Investigation of the impact of reducing the precision of the numerical scheme is analysed by following 3 indicators of the physics solved by the code, namely the plasma response to an external high frequency electric field wave. The response of the distribution function in the vicinity of the particle-wave resonance is found to be most sensitive to the resolution. Consistently, a rapid growth of the error indicator determined with PoPe is observed. However, no critical value of this indicator allowing us to retain the physics in a situation of degraded precision could be observed. The response of the amplitude of the electric potential fluctuations is characterised by a transient growth followed by a plateau. It is found that the loss of this plateau is governed by the resolution in v-space, but due to the generation of a symmetry in the problem rather than to errors in the numerical scheme. The analysis of the transient indicates that the growth rate of the amplitude of the electric potential is very robust down to very low resolution, step in velocity of 2 thermal velocities. However, a transition prior to this resolution, with step 0.5 thermal velocity, can be identified corresponding to a PoPe indicator of order zero, namely for errors of order 100 %.
Thomas Cartier-Michaud, Philippe Ghendrih, Guilhem Dif-Pradalier, Xavier Garbet, Virginie Grandgirard, et al.. Verification of turbulent simulations using PoPe: quantifying model precision and numerical error with data mining of simulation output. Journal of Physics: Conference Series, 2018, 1125, pp.012005. ⟨10.1088/1742-6596/1125/1/012005⟩. ⟨hal-02196674⟩
Denis Martinand, Eric Serre, Richard M. Lueptow. Linear and weakly nonlinear analyses of cylindrical Couette flow with axial and radial flows. Journal of Fluid Mechanics, 2017, 824, pp.438 - 476. ⟨10.1017/jfm.2017.351⟩. ⟨hal-01592948⟩ Plus de détails...
Extending previous linear stability analyses of the instabilities developing in permeable Taylor-Couette-Poiseuille flows where axial and radial throughflows are superimposed on the usual Taylor-Couette flow, we further examine the linear behaviour and expand the analysis to consider the weakly nonlinear behaviour of convective-type instabilities by means of the derivation of the fifth-order amplitude equation together with direct numerical simulations. Special attention is paid to the influence of the radius ratio eta = r(in)/r(out), and particularly to wide gaps (small eta) and how they magnify the effects of the radial flow. The instabilities take the form of pairs of counter-rotating toroidal vortices superseded by helical ones as the axial flow is increased. Increasing the radial inflow draws these vortices near the inner cylinder, where they shrink relative to the annular gap, when this gap is wide. Strong axial and radial flows in a narrow annular gap lead to a very large azimuthal wavenumber with steeply sloped helical vortices. Strong radial outflow in a wide annular gap results in very large helical vortices. The analytical and numerical saturated vortices match quite well. In addition, radial inflows or outflows can turn the usually supercritical bifurcation from laminar to vortical flow into a subcritical one. The radial flow above which this change occurs decreases as the radius ratio eta decreases. A practical motivation for this weakly nonlinear analysis is found in modelling dynamic filtration devices, which rely on vortical instabilities to reduce the processes of accumulation on their membranes.
Denis Martinand, Eric Serre, Richard M. Lueptow. Linear and weakly nonlinear analyses of cylindrical Couette flow with axial and radial flows. Journal of Fluid Mechanics, 2017, 824, pp.438 - 476. ⟨10.1017/jfm.2017.351⟩. ⟨hal-01592948⟩
P. Tamain, C. Colin, L. Colas, C. Baudoin, G. Ciraolo, et al.. Numerical analysis of the impact of an RF sheath on the Scrape-Off Layer in 2D and 3D turbulence simulations. Nuclear Materials and Energy, 2017, 12, pp.1171 - 1177. ⟨10.1016/j.nme.2016.12.022⟩. ⟨hal-01702267⟩ Plus de détails...
Motivated by Radio Frequency (RF) heating studies, the response of the plasma of tokamaks to the presence of a locally polarized limiter is studied. In a first part, we use the TOKAM3X 3D global edge turbulence code to analyse the impact of such biasing in a realistic geometry. Key features of experimental observations are qualitatively recovered, especially the extension of a potential and density perturbation on long, but finite, distances along connected field lines. The perturbation is also found to extend in the transverse direction. Both observations demonstrate the influence of perpendicular current loops on the plasma confirming the need for an accurate description in reduced models. In a second part, we use the TOKAM2D slab turbulence code to determine the validity of using a transverse Ohm's law for this purpose. Results indicate that a local Ohm's law with a constant and uniform perpendicular resistivity appears at least as an oversimplified description of perpendicular charge transport in a turbulent Scrape-Off Layer.
P. Tamain, C. Colin, L. Colas, C. Baudoin, G. Ciraolo, et al.. Numerical analysis of the impact of an RF sheath on the Scrape-Off Layer in 2D and 3D turbulence simulations. Nuclear Materials and Energy, 2017, 12, pp.1171 - 1177. ⟨10.1016/j.nme.2016.12.022⟩. ⟨hal-01702267⟩
W.A. Gracias, P. Tamain, Eric Serre, R.A. Pitts, L. Garcia. The impact of magnetic shear on the dynamics of a seeded 3D filament in slab geometry. Nuclear Materials and Energy, 2017, 12, pp.798 - 807. ⟨10.1016/j.nme.2017.02.022⟩. ⟨hal-01702187⟩ Plus de détails...
Seeded filament simulations are used to study blob dynamics with the state-of-the-art TOKAM3X fluid code in the scrape-off layer (SOL) using a slab geometry. The filamentary dynamics recovered with the code are compared with previously predicted analytical blob velocity scalings while also studying the effect of field line pitch angle on these dynamics and are found to be similar. The effect of changing magnetic topology on filamentary motion is also investigated. Magnetic shear is introduced in the model by the sudden and localised variation of field line pitch angle for a narrow radially located region constituting effectively a shearing zone. Three such shear zones are tested to see how they affect filament motion. Filaments are initialised radially upstream from the shear zone and recorded as they convect towards the far-SOL side. The lowest intensity shear zone allows many of the higher amplitude filaments to pass through after dampening them. On the other hand, the highest intensity shear zones prevent all filaments from progressing to the wall beyond the shear zone and, in certain cases for high density amplitude filaments, is able to generate a new filament downstream from the shear zone.
W.A. Gracias, P. Tamain, Eric Serre, R.A. Pitts, L. Garcia. The impact of magnetic shear on the dynamics of a seeded 3D filament in slab geometry. Nuclear Materials and Energy, 2017, 12, pp.798 - 807. ⟨10.1016/j.nme.2017.02.022⟩. ⟨hal-01702187⟩
Y. Marandet, H. Bufferand, N. Nace, M. Valentinuzzi, G. Ciraolo, et al.. Towards a consistent modelling of plasma edge turbulence in mean field transport codes: Focus on sputtering and plasma fluctuations. Nuclear Materials and Energy, 2017, 12, pp.931 - 934. ⟨10.1016/j.nme.2017.02.007⟩. ⟨hal-01702229⟩ Plus de détails...
Transport codes are the main workhorses for global edge studies and modern divertor design. These tools do not resolve turbulent fluctuations responsible for the bulk of cross-field transport in the Scrape-off Layer (SOL), and solve mean field equations instead. Turbulent fluxes are modelled by diffusive transport along the gradients of the mean fields. Improvements of this description, on the basis of approaches developed in computational fluid dynamics are discussed, broadening the outlook given in Bufferand et al. (2016) [10]. This contribution focuses on additional closure issues related to non-linearities in sources/sinks from plasma-wall interactions, here sputtered fluxes from the plasma facing components. “Fluctuation dressed” sputtering yields Yeff are introduced and calculated from turbulence simulations. Properly taking fluctuations into account is shown to lead to higher sputtering at sub-threshold energies compared to mean field predictions. As a first step towards an implementation in a transport code, the possibility of parametrizing Yeff in terms of the mean fields is tentatively investigated.
Y. Marandet, H. Bufferand, N. Nace, M. Valentinuzzi, G. Ciraolo, et al.. Towards a consistent modelling of plasma edge turbulence in mean field transport codes: Focus on sputtering and plasma fluctuations. Nuclear Materials and Energy, 2017, 12, pp.931 - 934. ⟨10.1016/j.nme.2017.02.007⟩. ⟨hal-01702229⟩
Eddy Constant, Julien Favier, Marcello Meldi, Philippe Meliga, Eric Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers and Fluids, 2017, 157, pp.55 - 72. ⟨10.1016/j.compfluid.2017.08.001⟩. ⟨hal-01591562⟩ Plus de détails...
The present work proposes a modified Pressure-Implicit Split-Operator (PISO) solver integrating the recent Immersed Boundary Method (IBM) proposed by Pinelli et al. [1] in order to perform reliable simulations of incompressible flows around bluff bodies using the open source toolbox OpenFOAM version 2.2 (ESI-OpenCFD [2]). The (IBM) allows for a precise representation of fixed and moving solid obstacles embedded in the physical domain, using uniform or stretched Cartesian meshes. Owing to this feature, the maximum level of accuracy and scalability of the numerical solvers can be systematically achieved. An iterative scheme based on sub-iterations between (IBM) and pressure correction has been implemented in the native (PISO) solver of OpenFOAM. This allows one to use fast optimized Poisson solvers while satisfying simultaneously the divergence-free flow state and the no-slip condition at the body surface. To compute the divergence of the momentum equation (in the PISO loop) and the interpolation of the fluxes, we propose an hybrid calculation with an analytical resolution (using the kernel function equation) of the quantities involving the force term (singular quantities). A careful and original verification study has been carried out which allows to estimate three different errors related to the discretization and to the (IBM). Various 2D and 3D well-documented test cases of academic flows around fixed or moving cylinders have been simulated and carefully validated against existing data from the literature in a large range of Reynolds numbers, Re = 30 − 3900 and in the frame of DNS and DDES OpenFOAM native models.
Eddy Constant, Julien Favier, Marcello Meldi, Philippe Meliga, Eric Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers and Fluids, 2017, 157, pp.55 - 72. ⟨10.1016/j.compfluid.2017.08.001⟩. ⟨hal-01591562⟩
G. Ciraolo, H. Bufferand, J. Bucalossi, Ph. Ghendrih, P. Tamain, et al.. H-mode WEST tungsten divertor operation: deuterium and nitrogen seeded simulations with SOLEDGE2D-EIRENE. Nuclear Materials and Energy, 2017, 12, pp.187 - 192. ⟨10.1016/j.nme.2016.12.025⟩. ⟨hal-01702237⟩ Plus de détails...
Simulations of WEST H-mode divertor scenarios have been performed with SOLEDGE2D-EIRENE edge plasma transport code, both for pure deuterium and nitrogen seeded discharge. In the pure deuterium case, a target heat flux of 8 MW/m2 is reached, but misalignment between heat and the particle outflux yields 50 eV plasma temperature at the target plates. With nitrogen seeding, the heat and particle outflux are observed to be aligned so that lower plasma temperatures at the target plates are achieved together with the required high heat fluxes. This change in heat and particle outflux alignment is analysed with respect to the role of divertor geometry and the impact of vertical vs horizontal target plates on neutrals spreading.
G. Ciraolo, H. Bufferand, J. Bucalossi, Ph. Ghendrih, P. Tamain, et al.. H-mode WEST tungsten divertor operation: deuterium and nitrogen seeded simulations with SOLEDGE2D-EIRENE. Nuclear Materials and Energy, 2017, 12, pp.187 - 192. ⟨10.1016/j.nme.2016.12.025⟩. ⟨hal-01702237⟩
Davide Galassi, P. Tamain, C. Baudoin, H. Bufferand, G. Ciraolo, et al.. Flux expansion effect on turbulent transport in 3D global simulations. Nuclear Materials and Energy, 2017, 12, pp.953 - 958. ⟨10.1016/j.nme.2017.01.008⟩. ⟨hal-01702255⟩ Plus de détails...
The flux expansion effect on the Scrape-Off Layer equilibrium is inspected through TOKAM3X 3D turbulence simulations. Three magnetic equilibria with analytically controlled flux expansion are built, representing respectively a positive, a null and a negative Shafranov shift. Turbulent E × B fluxes across flux surfaces show similar amplitudes and poloidal distributions in all cases. The ballooning nature of the interchange instability is recovered, with an enhancement of turbulence in the vicinity of the limiter, probably due to a Kelvin–Helmoltz instability. Interestingly, the poloidally averaged density decay length is found to be shorter almost by a factor 2 in the case of flux surfaces compressed at the low-field side midplane, with respect to the opposite case, indicating the presence of unfavorable conditions for the turbulent transport. The difference in the magnetic field line shape is pointed out as a mechanism which affects the turbulent transport across the flux surfaces. Indeed the unstable region has a larger parallel extension when flux expansion in the low-field side is larger. Moreover, the configuration with a lower magnetic shear at the low-field side midplane shows a more unstable behavior. The role of this parameter in turbulence stabilization is qualitatively evaluated. The difference in the distribution of transport along the parallel direction is shown to affect also the parallel flows, which are analyzed for the three proposed cases.
Davide Galassi, P. Tamain, C. Baudoin, H. Bufferand, G. Ciraolo, et al.. Flux expansion effect on turbulent transport in 3D global simulations. Nuclear Materials and Energy, 2017, 12, pp.953 - 958. ⟨10.1016/j.nme.2017.01.008⟩. ⟨hal-01702255⟩
Congshan Zhuo, Pierre Sagaut. Acoustic multipole sources for the regularized lattice Boltzmann method: Comparison with multiple-relaxation-time models in the inviscid limit. Physical Review E , 2017, 95 (6), pp.063301. ⟨10.1103/PhysRevE.95.063301⟩. ⟨hal-01548424⟩ Plus de détails...
Congshan Zhuo, Pierre Sagaut. Acoustic multipole sources for the regularized lattice Boltzmann method: Comparison with multiple-relaxation-time models in the inviscid limit. Physical Review E , 2017, 95 (6), pp.063301. ⟨10.1103/PhysRevE.95.063301⟩. ⟨hal-01548424⟩
Alekseenko Elena, Bernard Roux. Submerged Aquatic Vegetation Restoration in Brackish Ecosystems Subject to Strong Winds and Coastal Jets. Oceanography & Fisheries Open access Journal, 2017, 2 (4), pp.555595. ⟨10.19080/OFOAJ.2017.02.555595⟩. ⟨hal-01813859⟩ Plus de détails...
The bottom shear stress (BSS) in a windy Mediterranean lagoon has been carefully investigated through numerical modelling. BSS maps have been obtained for the entire lagoon. The aim is to compare BSS with its critical value in the near shoreareas selected for SAV replanting which are subject to downwind coastal jets.
Alekseenko Elena, Bernard Roux. Submerged Aquatic Vegetation Restoration in Brackish Ecosystems Subject to Strong Winds and Coastal Jets. Oceanography & Fisheries Open access Journal, 2017, 2 (4), pp.555595. ⟨10.19080/OFOAJ.2017.02.555595⟩. ⟨hal-01813859⟩
Journal: Oceanography & Fisheries Open access Journal
Davide Galassi, P. Tamain, H. Bufferand, Guido Ciraolo, Ph. Ghendrih, et al.. Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry. Nuclear Fusion, 2017, 57 (3), pp.036029. ⟨10.1088/1741-4326/aa5332⟩. ⟨hal-01592945⟩ Plus de détails...
The poloidal asymmetries of parallel flows in edge plasmas are investigated by the 3D fluid turbulence code TOKAM3X. A diverted COMPASS-like magnetic equilibrium is used for the simulations. The measurements and simulations of parallel Mach numbers are compared, and exhibit good qualitative agreement. Small-scale turbulent transport is observed to dominate near the low field side midplane, even though it co-exists with significant large-scale cross-field fluxes. Despite the turbulent nature of the plasma in the divertor region, simulations show the low effectiveness of turbulence for the cross-field transport towards the private flux region. Nevertheless, a complex pattern of fluxes associated with the average field components are found to cross the separatrix in the divertor region. Large-scale and small-scale turbulent E x B transport, along with the del B drift, drive the asymmetries in parallel flows. A semian-alytical model based on mass and parallel momentum balances allows the poloidal drift effects on the asymmetry pattern to be evaluated. As in the experiments, a reversed B-T simulation provides a way of self-consistently separating the effects of turbulent transport and large-scale flows, which must be reversed for a reversed field. The large-scale contribution is found to be responsible for typically 50% of the effect on the Mach number, evaluated at the top of the machine. The presented picture shows the complex interplay between drifts and turbulence, underlining the necessity of a global approach to edge plasma modelling, including a self-consistent description of the turbulence.
Davide Galassi, P. Tamain, H. Bufferand, Guido Ciraolo, Ph. Ghendrih, et al.. Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry. Nuclear Fusion, 2017, 57 (3), pp.036029. ⟨10.1088/1741-4326/aa5332⟩. ⟨hal-01592945⟩
R.J.A. Howard, Eric Serre. Large eddy simulation in Code_Saturne of thermal mixing in a T junction with brass walls. International Journal of Heat and Fluid Flow, 2017, 63, pp.119 - 127. ⟨10.1016/j.ijheatfluidflow.2016.09.011⟩. ⟨hal-01592931⟩ Plus de détails...
Following on from Kuhn et al (2010) we study the capability of large eddy simulation with conjugate heat transfer to predict thermal fluctuations with thermal mixing. Wall functions are used to model the wall heat transfer. Comparison with experimental results show that the temperature variance on the outer skin of the solid is well predicted by the simulation. It is shown that the variance of thermal flux in the fluid closely maps the temperature variance at the outer boundary of the solid. Since the variance of thermal flux is closely related to the dissipation of temperature variance it can be concluded that the dissipation of temperature variance in the fluid is linked to temperature variance in the solid. Analysis of the equation of the temperature variance in the solid confirms this is indeed the case. It is the dissipation of temperature variance in the fluid that characterizes how the temperature variance penetrates the solid. Thus RANS modelling can be used to predict thermal variance in solids provided that there is an accurate model for the dissipation of temperature variance at the wall and an equation for the thermal variance in the solid is solved.
R.J.A. Howard, Eric Serre. Large eddy simulation in Code_Saturne of thermal mixing in a T junction with brass walls. International Journal of Heat and Fluid Flow, 2017, 63, pp.119 - 127. ⟨10.1016/j.ijheatfluidflow.2016.09.011⟩. ⟨hal-01592931⟩
Journal: International Journal of Heat and Fluid Flow
Hugo Bufferand, G. Ciraolo, P Di Cintio, N Fedorczak, Ph Ghendrih, et al.. Nonlocal heat flux application for Scrape-off Layer plasma. Contributions to Plasma Physics, In press. ⟨hal-01655295⟩ Plus de détails...
The nonlocal expression proposed by Luciani-Mora-Virmont is implemented into a 1D fluid model for the scrape-off layer. Analytic solutions for heat equation are discussed as well as the impact of sheath boundary conditions on the continuity of the temperature profile. The nonlocal heat flux is compared to Spitzer-Härm heat flux for different collisionality.
Hugo Bufferand, G. Ciraolo, P Di Cintio, N Fedorczak, Ph Ghendrih, et al.. Nonlocal heat flux application for Scrape-off Layer plasma. Contributions to Plasma Physics, In press. ⟨hal-01655295⟩
Hugo Bufferand, C Baudoin, J Bucalossi, G Ciraolo, Julien Denis, et al.. Implementation of drift velocities and currents in SOLEDGE2D-EIRENE. Nuclear Materials and Energy, 2017, 12, pp.852-857. ⟨hal-01372986⟩ Plus de détails...
In order to improve cross-field transport description, drifts and currents have been implemented in SOLEDGE2D-EIRENE. The derivation of an equation for the electric potential is recalled. The resolution of current equation is tested in a simple slab case. WEST divertor simulations in forward-B and reverse-B fields are also discussed. A significant increase of ExB shear is observed in the forward-B configuration that could explain a favorable L-H transition in this case.
Hugo Bufferand, C Baudoin, J Bucalossi, G Ciraolo, Julien Denis, et al.. Implementation of drift velocities and currents in SOLEDGE2D-EIRENE. Nuclear Materials and Energy, 2017, 12, pp.852-857. ⟨hal-01372986⟩
Philippe Meliga, Olivier Cadot, Eric Serre. Experimental and Theoretical Sensitivity Analysis of Turbulent Flow Past a Square Cylinder. Flow, Turbulence and Combustion, 2016, 97 (4, SI), pp.987-1015. ⟨10.1007/s10494-016-9755-0⟩. ⟨hal-01461791⟩ Plus de détails...
We assess experimentally and theoretically the ability of a small control cylinder to alter vortex shedding in turbulent flow past a square cylinder at R e = 22,000. Results are presented in terms of sensitivity maps showing the flow regions where the shedding frequency and amplitude are most affected by the control cylinder. Experimental results are obtained for a ratio 0.02 of the cylinder diameters, over an extended domain covering the wake, the shear layers and the free stream. The shedding frequency can be either decreased or increased, the largest effects being obtained placing the control cylinder at the outer edge of the detached shear layers (associated with frequency decrease) or upstream of the square cylinder (associated with frequency increase, in contrast with previous results obtained for a D-shaped geometry of the main cylinder). In contrast, the oscillation amplitude is rarely decreased, meaning that any variation of the shedding frequency comes at the expense of more intense vortex shedding. These findings are revisited in the frame of a theoretical, linear sensitivity analysis of the time-averaged mean flow, performed using adjoint methods in the frame of Reynolds-averaged Navier-Stokes modeling. We show that the retained approach carries valuable information in view of guiding efficient control strategy, as it allows identifying the main regions yielding either a decrease or an increase of the shedding frequency in striking agreement with the experiments. This is a tremendous timesaving in so far as the controlled states need not be computed, the overall computational cost being roughly that of computing the mean flow. In contrast, performing the sensitivity analysis on the underlying unstable steady state yields flawed predictions, hence stressing the need to encompass some level of mean coherent-coherent perturbations interaction in the linear model.
Philippe Meliga, Olivier Cadot, Eric Serre. Experimental and Theoretical Sensitivity Analysis of Turbulent Flow Past a Square Cylinder. Flow, Turbulence and Combustion, 2016, 97 (4, SI), pp.987-1015. ⟨10.1007/s10494-016-9755-0⟩. ⟨hal-01461791⟩
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Davide Galassi, et al.. The TOKAM3X code for edge turbulence fluid simulations of tokamak plasmas in versatile magnetic geometries. Journal of Computational Physics, 2016, 321, pp.606-623. ⟨10.1016/j.jcp.2016.05.038⟩. ⟨hal-01461797⟩ Plus de détails...
The new code TOKAM3X simulates plasma turbulence in full torus geometry including the open field lines of the Scrape-off Layer (SOL) and the edge closed field lines region in the vicinity of the separatrix. Based on drift-reduced Braginskii equations, TOKAM3X is able to simulate both limited and diverted plasmas. Turbulence is flux driven by incoming particles from the core plasma and no scale separation between the equilibrium and the fluctuations is assumed so that interactions between large scale flows and turbulence are consistently treated. Based on a domain decomposition, specific numerical schemes are proposed using conservative finite-differences associated to a semi-implicit time advancement. The process computation is multi-threaded and based on MPI and OpenMP libraries. In this paper, fluid model equations are presented together with the proposed numerical methods. The code is verified using the manufactured solution technique and validated through documented simple experiments. Finally, first simulations of edge plasma turbulence in X-point geometry are also introduced in a JET geometry. (C) 2016 Elsevier Inc. All rights reserved.
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Davide Galassi, et al.. The TOKAM3X code for edge turbulence fluid simulations of tokamak plasmas in versatile magnetic geometries. Journal of Computational Physics, 2016, 321, pp.606-623. ⟨10.1016/j.jcp.2016.05.038⟩. ⟨hal-01461797⟩
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Yannick Marandet, J. Bucalossi, et al.. Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D-EIRENE. Contributions to Plasma Physics, 2016, 56 (6-8), pp.555-562. ⟨10.1002/ctpp.201610033⟩. ⟨hal-01455239⟩ Plus de détails...
Cross-field transport in edge tokamak plasmas is known to be dominated by turbulent transport. A dedicated effort has been made to simulate this turbulent transport from first principle models but the numerical cost to run these simulations on the ITER scale remains prohibitive. Edge plasma transport study relies mostly nowadays on so-called transport codes where the turbulent transport is taken into account using effective ad-hoc diffusion coeffecients. In this contribution, we propose to introduce a transport equation for the turbulence intensity in SOLEDGE2D-EIRENE to describe the interchange turbulence properties. Going beyond the empirical diffusive model, this system automatically generates profiles for the turbulent transport and hence reduces the number of degrees of freedom for edge plasma transport codes. We draw inspiration from the k-epsilon model widely used in the neutral fluid community. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Yannick Marandet, J. Bucalossi, et al.. Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D-EIRENE. Contributions to Plasma Physics, 2016, 56 (6-8), pp.555-562. ⟨10.1002/ctpp.201610033⟩. ⟨hal-01455239⟩
R. Futtersack, C. Colin, Patrick Tamain, Guido Ciraolo, Philippe Ghendrih, et al.. First Principle Modelling of Interplay between Langmuir Probes and Plasma Turbulence. Contributions to Plasma Physics, 2016, 56 (6-8), pp.575-580. ⟨10.1002/ctpp.201610038⟩. ⟨hal-01455240⟩ Plus de détails...
The interplay between Langmuir probes (LP) and Scrape-Off-Layer plasma turbulence is numerically investigated with the TOKAM2D and TOKAM3X fluid codes. The LP is modelled by biasing a part of the target plates surface; we then study its impact on the turbulent transport 1) in presence of electron temperature fluctuations and 2) with a complete description of the parallel dynamics. We find that a biased probe can disturb local plasma parameters as well as turbulent transport in its vicinity, by polarizing the connected flux tube and thus driving a strong ExB vortex. Moreover, electron temperature fluctuations are found to account significantly those of floating potential, but with a limited impact on flux measurements depending on the probe's exact geometry. The 3D study of the problem shows the attenuation, but the persistency, of these perturbations induced by the presence of the LP. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
R. Futtersack, C. Colin, Patrick Tamain, Guido Ciraolo, Philippe Ghendrih, et al.. First Principle Modelling of Interplay between Langmuir Probes and Plasma Turbulence. Contributions to Plasma Physics, 2016, 56 (6-8), pp.575-580. ⟨10.1002/ctpp.201610038⟩. ⟨hal-01455240⟩
Patrick Tamain, Hugo Bufferand, L. Carbajal, Yannick Marandet, C. Baudoin, et al.. Interplay between Plasma Turbulence and Particle Injection in 3D Global Simulations. Contributions to Plasma Physics, 2016, 56 (6-8), pp.569-574. ⟨10.1002/ctpp.201610063⟩. ⟨hal-01455242⟩ Plus de détails...
The impact of a 3D localized particle source on the edge plasma in 3D global turbulence simulations is investigated using the TOKAM3X fluid code. Results apply to advanced fueling methods such as Supersonic Molecular Beam Injection (SMBI) or pellets injection. The fueling source is imposed as a volumetric particle source in the simulations so that the physics leading to the ionization of particles and its localization are not taken into account. As already observed in experiments, the localized particle source strongly perturbs both turbulence and the large scale organization of the edge plasma. The localized increase of the pressure generated by the source drives sonic parallel flows in the plasma, leading to a poloidal redistribution of the particles on the time scale of the source duration. However, the particle deposition also drives localized transverse pressure gradients which impacts the stability of the plasma with respect to interchange processes. The resulting radial transport occurs on a sufficiently fast time scale to compete with the parallel redistribution of particles, leading to immediate radial losses of a significant proportion of the injected particles. Low Field Side (LFS) and High Field Side (HFS) injections exhibit different dynamics due to their interaction with curvature. In particular, HFS particle deposition drives an inward flux leading to differences in the particle deposition efficiency (higher for HFS than LFS). These results demonstrate the importance of taking into account plasma transport in a self-consistent manner when investigating fueling methods. ((c) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Patrick Tamain, Hugo Bufferand, L. Carbajal, Yannick Marandet, C. Baudoin, et al.. Interplay between Plasma Turbulence and Particle Injection in 3D Global Simulations. Contributions to Plasma Physics, 2016, 56 (6-8), pp.569-574. ⟨10.1002/ctpp.201610063⟩. ⟨hal-01455242⟩
Yannick Marandet, Hugo Bufferand, G. Ciraolo, P. Genesio, P. Meliga, et al.. Effect of Statistical Noise on Simulation Results with a Plasma Fluid Code Coupled to a Monte Carlo Kinetic Neutral Code. Contributions to Plasma Physics, 2016, 56 (6-8), pp.604-609. ⟨10.1002/ctpp.201610009⟩. ⟨hal-01455237⟩ Plus de détails...
Power exhaust is one of the major challenges that future devices such as ITER and DEMO will face. Because of the lack of identified scaling parameters, predictions for divertor plasma conditions in these devices have to rely on detailed modelling. Most plasma edge simulations carried out so far rely on transport codes, which most of the times consist of a fluid code for the plasma coupled to a kinetic Monte Carlo (MC) code for neutral particles. One of the main difficulties in interpreting code results is the statistical noise from the MC procedure, which makes it difficult to define a convergence criterion for the simulations. In this work, we elaborate on similarities between noisy transport code simulations and turbulence simulations, and argue that the time averaged solution is a well defined stationary solution for the system. We illustrate these ideas with a simple slab test case with fluid neutrals, to which we add synthetic noise. In this case, the effects of noise are found to be significant only at high noise levels and for large enough correlations times.
Yannick Marandet, Hugo Bufferand, G. Ciraolo, P. Genesio, P. Meliga, et al.. Effect of Statistical Noise on Simulation Results with a Plasma Fluid Code Coupled to a Monte Carlo Kinetic Neutral Code. Contributions to Plasma Physics, 2016, 56 (6-8), pp.604-609. ⟨10.1002/ctpp.201610009⟩. ⟨hal-01455237⟩
Fabio Riva, Clothilde Colin, Julien Denis, Luke Easy, Ivo Furno, et al.. Blob dynamics in the TORPEX experiment: a multi-code validation. Plasma Physics and Controlled Fusion, 2016, 58 (4), ⟨10.1088/0741-3335/58/4/044005⟩. ⟨hal-01461784⟩ Plus de détails...
Three-dimensional and two-dimensional seeded blob simulations are performed with five different fluid models, all based on the drift-reduced Braginskii equations, and the numerical results are compared among themselves and validated against experimental measurements provided by the TORPEX device ( Fasoli et al 2006 Phys. Plasmas 13 055902). The five models are implemented in four simulation codes, typically used to simulate the plasma dynamics in the tokamak scrape-off layer, namely BOUT++ (Dudson et al 2009 Comput. Phys. Commun. 180 1467), GBS (Ricci et al 2012 Plasma Phys. Control. Fusion 54 124047), HESEL (Nielsen et al 2015 Phys. Lett. A 379 3097), and TOKAM3X (Tamain et al 2014 Contrib. Plasma Phys. 54 555). Three blobs with different velocities and different stability properties are simulated. The differences observed among the simulation results and the different levels of agreement with experimental measurements are investigated, increasing our confidence in our simulation tools and shedding light on the blob dynamics. The comparisons demonstrate that the radial blob dynamics observed in the three-dimensional simulations is in good agreement with experimental measurements and that, in the present experimental scenario, the two-dimensional model derived under the assumption of k(vertical bar vertical bar) = 0 is able to recover the blob dynamics observed in the three-dimensional simulations. Moreover, it is found that an accurate measurement of the blob temperature is important to perform reliable seeded blob simulations.
Fabio Riva, Clothilde Colin, Julien Denis, Luke Easy, Ivo Furno, et al.. Blob dynamics in the TORPEX experiment: a multi-code validation. Plasma Physics and Controlled Fusion, 2016, 58 (4), ⟨10.1088/0741-3335/58/4/044005⟩. ⟨hal-01461784⟩
J. Gounley, G. Boedec, Marc Jaeger, M. Leonetti. Influence of surface viscosity on droplets in shear flow. Journal of Fluid Mechanics, 2016, 791, pp.464- 494. ⟨10.1017/jfm.2016.39⟩. ⟨hal-01281643⟩ Plus de détails...
The behaviour of a single droplet in an immiscible external fluid, submitted to shear flow is investigated using numerical simulations. The surface of the droplet is modelled by a Boussinesq–Scriven constitutive law involving the interfacial viscosities and a constant surface tension. A numerical method using Loop subdivision surfaces to represent droplet interface is introduced. This method couples boundary element method for fluid flows and finite element method to take into account the stresses due to the surface dilational and shear viscosities and surface tension. Validation of the numerical scheme with respect to previous analytic and computational work is provided, with particular attention to the viscosity contrast and the shear and dilational viscosities characterized both by a Boussinesq number Bq. Then, influence of equal surface viscosities on steady-state characteristics of a droplet in shear flow are studied, considering both small and large deformations and for a large range of bulk viscosity contrast. We find that small deformation analysis is surprisingly predictive at moderate and high surface viscosities. Equal surface viscosities decrease the Taylor deformation parameter and tank-treading angle and also strongly modify the dynamics of the droplet: when the Boussinesq number (surface viscosity) is large relative to the capillary number (surface tension), the droplet displays damped oscillations prior to steady-state tank-treading, reminiscent from the behaviour at large viscosity contrast. In the limit of infinite capillary number Ca, such oscillations are permanent. The influence of surface viscosities on breakup is also investigated, and results show that the critical capillary number is increased. A diagram (Bq;Ca) of breakup is established with the same inner and outer bulk viscosities. Additionally, the separate roles of shear and dilational surface viscosity are also elucidated, extending results from small deformation analysis. Indeed, shear (dilational) surface viscosity increases (decreases) the stability of drops to breakup under shear flow. The steady-state deformation (Taylor parameter) varies nonlinearly with each Boussinesq number or a linear combination of both Boussinesq numbers. Finally, the study shows that for certain combinations of shear and dilational viscosities, drop deformation for a given capillary number is the same as in the case of a clean surface while the inclination angle varies.
J. Gounley, G. Boedec, Marc Jaeger, M. Leonetti. Influence of surface viscosity on droplets in shear flow. Journal of Fluid Mechanics, 2016, 791, pp.464- 494. ⟨10.1017/jfm.2016.39⟩. ⟨hal-01281643⟩
Julien Denis, B. Pégourié, J. Bucalossi, Hugo Bufferand, Guido Ciraolo, et al.. Wall surface temperature calculation in the SolEdge2D-EIRENE transport code. Physica Scripta, 2016, 15th International Conference on Plasma-Facing Materials and Components for Fusion Applications, T167, ⟨10.1088/0031-8949/T167/1/014073⟩. ⟨hal-01459103⟩ Plus de détails...
A thermal wall model is developed for the SolEdge2D-EIRENE edge transport code for calculating the surface temperature of the actively-cooled vessel components in interaction with the plasma. This is a first step towards a self-consistent evaluation of the recycling of particles, which depends on the wall surface temperature. The proposed thermal model is built to match both steady-state temperature and time constant of actively-cooled plasma facing components. A benchmark between this model and the Finite Element Modelling code CAST3M is performed in the case of an ITER-like monoblock. An example of application is presented for a SolEdge2D-EIRENE simulation of a medium-power discharge in the WEST tokamak, showing the steady-state wall temperature distribution and the temperature cycling due to an imposed Edge Localised Mode-like event.
Julien Denis, B. Pégourié, J. Bucalossi, Hugo Bufferand, Guido Ciraolo, et al.. Wall surface temperature calculation in the SolEdge2D-EIRENE transport code. Physica Scripta, 2016, 15th International Conference on Plasma-Facing Materials and Components for Fusion Applications, T167, ⟨10.1088/0031-8949/T167/1/014073⟩. ⟨hal-01459103⟩
Lyes Bordja, Emilia Crespo Del Arco, Éric Serre, Rachid Bessaih. EFFECTS OF AXIAL MAGNETIC FIELD AND THERMAL CONVECTION ON A COUNTERROTATING VON KARMAN FLOW. Heat Transfer Research, 2016, 47 (5), pp.471-488. ⟨10.1615/HeatTransRes.2016007441⟩. ⟨hal-01462070⟩ Plus de détails...
The effects of thermal convection and of a constant axial magnetic field on a von Karman flow driven by the exact counter-rotation of two lids are investigated in a vertical cylinder of aspect ratio Gamma(= height/radius) = 2 at a fixed Reynolds number Re(= Omega R-2/v) = 300. Direct numerical simulations are performed when varying separately the Rayleigh and Hartmann numbers in the range [0, 1800] and [0, 20], respectively, in the limit of the Boussinesq approximation and of a small magnetic Reynolds numbers, Re-m << 1. Without a magnetic field, the base flow symmetries of the von Karman flow are broken by thermal convection that becomes dominant in the range of Ra [500, 1000]. Three-dimensional solutions are characterized by the occurrence of a steady, m = 1, azimuthal mode exhibiting a cat's eye vortex in the circumferential plane. When increasing the Rayleigh number in the range [500, 1000], the vortex pulsates in an oscillatory manner, due to variations of the flow intensity. Otherwise, increasing the axial magnetic field intensity stabilizes the flow, and the oscillatory motion can be inhibited. Numerical solutions show that the critical Rayleigh number for transition increases linearly with the Hartmann number. Finally, results show that when varying the Rayleigh number, the structure of the electric potential can be strongly modified by thermal convection. Such an observation suggests new induction mechanisms in the case of small nonzero values of the magnetic Reynolds number.
Lyes Bordja, Emilia Crespo Del Arco, Éric Serre, Rachid Bessaih. EFFECTS OF AXIAL MAGNETIC FIELD AND THERMAL CONVECTION ON A COUNTERROTATING VON KARMAN FLOW. Heat Transfer Research, 2016, 47 (5), pp.471-488. ⟨10.1615/HeatTransRes.2016007441⟩. ⟨hal-01462070⟩
Achim Guckenberger, Marcel P. Schrame, Paul G. Chen, Marc Leonetti, Stephan Gekle. On the bending algorithms for soft objects in flows. Computer Physics Communications, 2016, 207, pp.1-23. ⟨10.1016/j.cpc.2016.04.018⟩. ⟨hal-01314722⟩ Plus de détails...
One of the most challenging aspects in the accurate simulation of three-dimensional soft objects such as vesicles or biological cells is the computation of membrane bending forces. The origin of this difficulty stems from the need to numerically evaluate a fourth order derivative on the discretized surface geometry. Here we investigate six different algorithms to compute membrane bending forces, including regularly used methods as well as novel ones. All are based on the same physical model (due to Canham and Helfrich) and start from a surface discretization with flat triangles. At the same time, they differ substantially in their numerical approach. We start by comparing the numerically obtained mean curvature, the Laplace-Beltrami operator of the mean curvature and finally the surface force density to analytical results for the discocyte resting shape of a red blood cell. We find that none of the considered algorithms converges to zero error at all nodes and that for some algorithms the error even diverges. There is furthermore a pronounced influence of the mesh structure: Discretizations with more irregular triangles and node connectivity present serious difficulties for most investigated methods. To assess the behavior of the algorithms in a realistic physical application, we investigate the deformation of an initially spherical capsule in a linear shear flow at small Reynolds numbers. To exclude any influence of the flow solver, two conceptually very different solvers are employed: the Lattice-Boltzmann and the Boundary Integral Method. Despite the largely different quality of the bending algorithms when applied to the static red blood cell, we find that in the actual flow situation most algorithms give consistent results for both hydrodynamic solvers. Even so, a short review of earlier works reveals a wide scattering of reported results for, e.g., the Taylor deformation parameter. Besides the presented application to biofluidic systems, the investigated algorithms are also of high relevance to the computer graphics and numerical mathematics communities.
Achim Guckenberger, Marcel P. Schrame, Paul G. Chen, Marc Leonetti, Stephan Gekle. On the bending algorithms for soft objects in flows. Computer Physics Communications, 2016, 207, pp.1-23. ⟨10.1016/j.cpc.2016.04.018⟩. ⟨hal-01314722⟩
Abir Bouledjouidja, Yasmine Masmoudi, Michelle Sergent, Vivek Trivedi, Abdeslam-Hassen Meniai, et al.. Drug loading of foldable commercial intraocular lenses using supercritical impregnation
. International Journal of Pharmaceutics, 2016, 500 (1-2), pp.85 - 99. ⟨10.1016/j.ijpharm.2016.01.016⟩. ⟨hal-01266557⟩ Plus de détails...
The drug delivery through intraocular lenses (IOLs) allows the combination of cataract surgery act and postoperative treatment in a single procedure. In order to prepare such systems, “clean” supercritical CO2 processes are studied for loading commercial IOLs with ophthalmic drugs. Ciprofloxacin (CIP, an antibiotic) and dexamethasone 21-phosphate disodium (DXP, an anti-inflammatory drug) were impregnated into foldable IOLs made from poly-2-hydroxyethyl methacrylate (P-HEMA). A first pre-treatment step was conducted in order to remove absorbed conditioning physiological solution. Supercritical impregnations were then performed by varying the experimental conditions. In order to obtain transparent IOLs and avoid the appearance of undesirable foaming, it was necessary to couple slow pressurization and depressurization phases during supercritical treatments. The impregnation yields were determined through drug release studies. For both drugs, release studies showdeep and reproducible impregnation for different diopters. For the system P-HEMA/CIP, a series of impregnations was performed to delimit the experimental range at two pressures (80 and 200 bar) in the presence or absence of ethanol as a co-solvent for two diopters (+5.0 D and +21.0 D). Increase in pressure in the absence of a co-solvent resulted in improved CIP impregnation. The addition of ethanol (5 mol%) produced impregnation yields comparable to those obtained at 200 bar without co-solvent. A response surface methodology based on experimental designs was used to study the influence of operating conditions on impregnation of IOLs (+21.0 D) in the absence of co-solvent. Two input variables with 5 levels each were considered; the pressure (80–200 bar) and the impregnation duration (30–240 min). CIP impregnation yields ranging between 0.92 and 3.83 μgCIP/mgIOL were obtained from these experiments and response surface indicated the pressure as a key factor in the process. The DXP impregnation in P-HEMA was higher than CIP at all the tested conditions (8.50–14.53 μgDXP/mgIOL). Furthermore, unlike CIP, highest DXP impregnation yields were obtained in the presence of ethanol as a co-solvent (5 mol%). NMR spectroscopy was performed to confirm complete removal of ethanol in the co-solvent-treated IOLs
Abir Bouledjouidja, Yasmine Masmoudi, Michelle Sergent, Vivek Trivedi, Abdeslam-Hassen Meniai, et al.. Drug loading of foldable commercial intraocular lenses using supercritical impregnation
. International Journal of Pharmaceutics, 2016, 500 (1-2), pp.85 - 99. ⟨10.1016/j.ijpharm.2016.01.016⟩. ⟨hal-01266557⟩
Patrick Tamain, Philippe Ghendrih, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, et al.. Multi-scale self-organisation of edge plasma turbulent transport in 3D global simulations. Plasma Physics and Controlled Fusion, 2015, 57 (5), pp.054014. ⟨10.1088/0741-3335/57/5/054014⟩. ⟨hal-01299732⟩ Plus de détails...
The 3D global edge turbulence code TOKAM3X is used to study the properties of edge particle turbulent transport in circular limited plasmas, including both closed and open flux surfaces. Turbulence is driven by an incoming particle flux from the core plasma and no scale separation between the equilibrium and the fluctuations is assumed. Simulations show the existence of a complex self-organization of turbulence transport coupling scales ranging from a few Larmor radii up to the machine scale. Particle transport is largely dominated by small scale turbulence with fluctuations forming quasi field-aligned filaments. Radial particle transport is intermittent and associated with the propagation of coherent structures on long distances via avalanches. Long range correlations are also found in the poloidal and toroidal direction. The statistical properties of fluctuations vary with the radial and poloidal directions, with larger fluctuation levels and intermittency found in the outboard scrape-off layer (SOL). Radial turbulent transport is strongly ballooned, with 90% of the flux at the separatrix flowing through the low-field side. One of the main consequences is the existence of quasi-sonic asymmetric parallel flows driving a net rotation of the plasma. Simulations also show the spontaneous onset of an intermittent E × B rotation characterized by a larger shear at the separatrix. Strong correlation is found between the turbulent particle flux and the E × B flow shear in a phenomenology reminiscent of H-mode physics. The poloidal position of the limiter is a key player in the observed dynamics.
Patrick Tamain, Philippe Ghendrih, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, et al.. Multi-scale self-organisation of edge plasma turbulent transport in 3D global simulations. Plasma Physics and Controlled Fusion, 2015, 57 (5), pp.054014. ⟨10.1088/0741-3335/57/5/054014⟩. ⟨hal-01299732⟩
R. Trozzo, G. Boedec, M. Leonetti, M. Jaeger. Axisymmetric Boundary Element Method for vesicles in a capillary. Journal of Computational Physics, 2015, 289, pp.62-82. ⟨10.1016/j.jcp.2015.02.022⟩. ⟨hal-01281961⟩ Plus de détails...
The problem of a vesicle transported by a fluid flow can present a large range of length scales. One example is the case of a vesicle producing a tether, and eventually pearls, in an elongational flow. Another case occurs when a lubrication film is formed, such as during the short range interaction between two vesicles. Such problems are still challenging for 3D simulations. On the other hand, a good understanding could be obtained by first considering the axisymmetric regime when such a regime exists. An axisymmetric model could then be used, without the criticisms that can be made of a 2D approach. We propose such a model, primarily interested in flows through narrow cylindrical capillaries. Two options are compared, with and without explicit representation of the capillary boundaries by a mesh. The numerical effort is characterized as a function of the vesicle’s initial shape, the flow magnitude and the confinement. The model is able to treat typical configurations of red blood cells flowing through very narrow pores with extremely thin lubrication films.
R. Trozzo, G. Boedec, M. Leonetti, M. Jaeger. Axisymmetric Boundary Element Method for vesicles in a capillary. Journal of Computational Physics, 2015, 289, pp.62-82. ⟨10.1016/j.jcp.2015.02.022⟩. ⟨hal-01281961⟩
Clothilde Colin, Patrick Tamain, Frederic Schwander, Eric Serre, Hugo Bufferand, et al.. Impact of the plasma-wall contact position on edge turbulent transport and poloidal asymmetries in 3D global turbulence simulations. Journal of Nuclear Materials, 2015, 463, pp.654-658. ⟨10.1016/j.jnucmat.2015.01.019⟩. ⟨hal-01225200⟩ Plus de détails...
A 3D global turbulence fluid code, TOKAM3X is used to investigate the effect of the limiter position on the edge plasma parallel flows and density profiles. Six configurations with different poloidal contact points in the machine are considered. For each one, asymmetric quasi-sonic parallel flows are found, owing to the ballooning of radial turbulent transport around the LFS mid-plane. In spite of the relative simplicity of the model used (isothermal, sheat-limited, no recycling), simulations exhibit trends in-line with experimental findings. Reversal of the flows is found when the limiter is moved from −30° under to 30° above the outboard mid-plane. The SOL width varies with the poloidal location and depends notably on the poloidal position of the limiter. Turbulence itself is shown to be impacted by the position of the limiter, radial transport appearing less ballooned with a LFS limiter than with a HFS.
Clothilde Colin, Patrick Tamain, Frederic Schwander, Eric Serre, Hugo Bufferand, et al.. Impact of the plasma-wall contact position on edge turbulent transport and poloidal asymmetries in 3D global turbulence simulations. Journal of Nuclear Materials, 2015, 463, pp.654-658. ⟨10.1016/j.jnucmat.2015.01.019⟩. ⟨hal-01225200⟩
R. Leybros, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Investigation of drift velocity effects on the EDGE and SOL transport. Journal of Nuclear Materials, 2015, 463, pp.489-492. ⟨10.1016/j.jnucmat.2014.10.079⟩. ⟨hal-01225211⟩ Plus de détails...
To understand the mechanisms behind poloidal asymmetries of the transport in the edge and SOL plasma, it is important to take into account drift velocity in the transport model. We investigate the effects of an imposed radial electric field on the plasma equilibrium in the transport code SOLEDGE2D. In the edge, we show an important modification of the flow pattern due to poloidal E × B drift velocity. The drift velocity generates asymmetry of the density through the Pfirsch–Schluter flows which creates an important parallel rotation through the viscous balance. In comparison to heat load imbalance studies in the SOL of divertor tokamak, a strong link between the amplitude of the radial electric field and the heat load imbalance in the SOL of limiter tokamak has been highlighted using different amplitude of the imposed radial electric field.
R. Leybros, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Investigation of drift velocity effects on the EDGE and SOL transport. Journal of Nuclear Materials, 2015, 463, pp.489-492. ⟨10.1016/j.jnucmat.2014.10.079⟩. ⟨hal-01225211⟩
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, P. Genesio, et al.. Comparison on heat flux deposition between carbon and tungsten wall – Investigations on energy recycling. Journal of Nuclear Materials, 2015, 463, pp.420-423. ⟨10.1016/j.jnucmat.2014.09.061⟩. ⟨hal-01225205⟩ Plus de détails...
The influence of the plasma facing components material on the scrape-off layer plasma is investigated. In particular, the energy recycling is found to be more pronounced for tungsten wall compared with carbon wall. Edge plasma simulations performed with the transport code SOLEDGE2D-EIRENE show that this enhanced energy recycling in the tungsten case leads to an increase of the scrape-off layer temperature. Moreover, the energy recycling depends on the ion angle of incidence with the wall. A PIC code has been used to model the ion acceleration in the magnetic pre-sheath and determine the later angle of incidence. These simulations show that ions mostly impact the wall with rather shallow incident angles leading to a further increase of the energy recycling.
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, P. Genesio, et al.. Comparison on heat flux deposition between carbon and tungsten wall – Investigations on energy recycling. Journal of Nuclear Materials, 2015, 463, pp.420-423. ⟨10.1016/j.jnucmat.2014.09.061⟩. ⟨hal-01225205⟩
Hugo Bufferand, Guido Ciraolo, Yannick Marandet, Jérome Bucalossi, Philippe Ghendrih, et al.. Numerical modelling for divertor design of the WEST device with a focus on plasma–wall interactions. Nuclear Fusion, 2015, 55 (5), pp.053025. ⟨hal-01225195⟩ Plus de détails...
In the perspective of operating tungsten monoblocks in WEST, the ongoing major upgrade of the Tore Supra tokamak, a dedicated modelling effort has been carried out to simulate the interaction between the edge plasma and the tungsten wall. A new transport code, SolEdge2D–EIRENE, has been developed with the ability to simulate the plasma up to the first wall. This is especially important for steady state operation, where thermal loads on all the plasma facing components, even remote from the plasma, are of interest. Moreover, main chamber tungsten sources are thought to dominate the contamination of the plasma core. We present here in particular new developments aimed at improving the description of the interface between the plasma and the wall, namely a way to treat sheath physics in a more faithful way using the output of 1D particle in cell simulations. Moreover, different models for prompt redeposition have been implemented and are compared. The latter is shown to play an important role in the balance between divertor and main chamber sources.
Hugo Bufferand, Guido Ciraolo, Yannick Marandet, Jérome Bucalossi, Philippe Ghendrih, et al.. Numerical modelling for divertor design of the WEST device with a focus on plasma–wall interactions. Nuclear Fusion, 2015, 55 (5), pp.053025. ⟨hal-01225195⟩
Richard Howard, Eric Serre. Large-eddy simulation in a mixing tee junction: High-order turbulent
statistics analysis. International Journal of Heat and Fluid Flow, 2015, 51, pp.65-77. ⟨hal-01138803⟩ Plus de détails...
This study analyses the mixing and thermal fluctuations induced in a mixing tee junction with circular cross-sections when cold water flowing in a pipe is joined by hot water from a branch pipe. This config- uration is representative of industrial piping systems in which temperature fluctuations in the fluid may cause thermal fatigue damage on the walls. Implicit large-eddy simulations (LES) are performed for equal inflow rates corresponding to a bulk Reynolds number Re= 39,080. Two different thermal boundary conditions are studied for the pipe walls; an insulating adiabatic boundary and a conducting steel wall boundary. The predicted flow structures show a satisfactory agreement with the literature. The velocity and thermal fields (including high-order statistics) are not affected by the heat transfer with the steel walls. However, predicted thermal fluctuations at the boundary are not the same between the flow and the solid, showing that solid thermal fluctuations cannot be predicted by the knowledge of the fluid thermal fluctuations alone. The analysis of high-order turbulent statistics provides a better understand- ing of the turbulence features. In particular, the budgets of the turbulent kinetic energy and temperature variance allows a comparative analysis of dissipation, production and transport terms. It is found that the turbulent transport term is an important term that acts to balance the production. We therefore use a priori tests to evaluate three different models for the triple correlation
Richard Howard, Eric Serre. Large-eddy simulation in a mixing tee junction: High-order turbulent
statistics analysis. International Journal of Heat and Fluid Flow, 2015, 51, pp.65-77. ⟨hal-01138803⟩
Journal: International Journal of Heat and Fluid Flow
H Guillard, M Bilanceri, C Colin, Philippe Ghendrih, G Giorgiani, et al.. Parallel Kelvin-Helmholtz instability in edge plasma. Journal of Physics: Conference Series, 2014, Joint Varenna-Lausanne International Workshop 2014, 561, pp.012009. ⟨10.1088/1742-6596/561/1/012009⟩. ⟨hal-01100365⟩ Plus de détails...
In the scrape-off layer (SOL) of tokamaks, the flow acceleration due to the presence of limiter or divertor plates rises the plasma velocity in a sonic regime. These high velocities imply the presence of a strong shear between the SOL and the core of the plasma that can possibly trigger some parallel shear flow instability. The existence of these instabilities, denoted as parallel Kelvin-Helmholtz instability in some works [1, 2] have been investigated theoretically in [3] using a minimal model of electrostatic turbulence composed of a mass density and parallel velocity equations. This work showed that the edge plasma around limiters might indeed be unstable to this type of parallel shear flow instabilities. In this work, we perform 3D simulations of the same simple mathematical model to validate an original finite volume numerical method aimed to the numerical study of edge plasma. This method combines the use of triangular unstructured meshes in the poloidal section and structured meshes in the toroidal direction and is particularly suited to the representation of the real complex geometry of the vacuum chamber of a tokamak. The numerical results confirm that in agreement with the theoretical expectations as well as with other numerical methods, the sheared flows in the SOL are subject to parallel Kelvin-Helmholtz instabilities. However, the growth rate of these instabilities is low and these computations require both a sufficient spatial resolution and a long simulation time. This makes the simulation of parallel Kelvin-Helmholtz instabilities a demanding benchmark.
H Guillard, M Bilanceri, C Colin, Philippe Ghendrih, G Giorgiani, et al.. Parallel Kelvin-Helmholtz instability in edge plasma. Journal of Physics: Conference Series, 2014, Joint Varenna-Lausanne International Workshop 2014, 561, pp.012009. ⟨10.1088/1742-6596/561/1/012009⟩. ⟨hal-01100365⟩
Denis Martinand, Eric Serre, Richard M. Lueptow. Mechanisms for the transition to waviness for Taylor vortices. Physics of Fluids, 2014, 26 (9), pp.094102. ⟨10.1063/1.4895400⟩. ⟨hal-01300402⟩ Plus de détails...
Building on the weakly nonlinear amplitude equation of the saturated Taylor vortices developing in a Taylor–Couette cell with a rotating inner cylinder and a fixed outer one, the physical mechanism underlying the destabilization of these vortices resulting in azimuthal waviness is addressed using Floquet analysis. For narrow gap configurations, analysis and direct numerical simulations together with existing experimental results support the idea that the waviness is generated by the axial shear in the azimuthal velocity due to the alternate advection by the Taylor vortices of azimuthal momentum between the cylinders. For wide gap configurations, this mechanism is no longer able to drive the azimuthal waviness and a different mechanism tends to select a subharmonic instability.
Denis Martinand, Eric Serre, Richard M. Lueptow. Mechanisms for the transition to waviness for Taylor vortices. Physics of Fluids, 2014, 26 (9), pp.094102. ⟨10.1063/1.4895400⟩. ⟨hal-01300402⟩
Jose Joaquin Sanchez-Alvarez, Eric Serre, Emilia Crespo Del Arco, Friedrich.H Busse. Geometry effects on Rayleigh-Benard convection in rotating annular ă layers. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2014, 89 (6), ⟨10.1103/PhysRevE.89.063013⟩. ⟨hal-01464703⟩ Plus de détails...
Rayleigh-Benard convection is investigated in rotating annular cavities ă at a moderate dimensionless rotation rate Omega = 60. The onset of ă convection is in the form of azimuthal traveling waves that set in at ă the sidewalls and at values of the Rayleigh number significantly below ă the value of the onset of convection in an infinitely extended layer. ă The present study addresses the effects of curvature and confinement on ă the onset of sidewall convection by using three-dimensional spectral ă solutions of the Oberbeck-Boussinesq equations. Such solutions ă demonstrate that the curvature of the outer boundary promotes the onset ă of the wall mode, while the opposite curvature of the inner boundary ă tends to delay the onset of the wall mode. An inner sidewall with a ă radius as low as one tenth of its height is sufficient, however, to ă support the onset of a sidewall mode. When radial confinement is ă increased the two independent traveling waves interact and eventually ă merge to form a nearly steady pattern of convection.
Jose Joaquin Sanchez-Alvarez, Eric Serre, Emilia Crespo Del Arco, Friedrich.H Busse. Geometry effects on Rayleigh-Benard convection in rotating annular ă layers. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2014, 89 (6), ⟨10.1103/PhysRevE.89.063013⟩. ⟨hal-01464703⟩
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Philippe Ghendrih, et al.. 3D properties of edge turbulent transport in full-torus simulations and their impact on poloidal asymmetries. Contributions to Plasma Physics, 2014, 54 (4-6), pp.555-559. ⟨10.1002/ctpp.201410017⟩. ⟨hal-01053290⟩ Plus de détails...
The 3D fluid turbulence code TOKAM3X is used to investigate the 3D properties of edge turbulent transport and their impact on poloidal asymmetries. Simulations are run in circular limited plasmas in a domain covering both closed and open flux surfaces. Turbulence characteristics exhibit large inhomogeneities both in the radial and poloidal directions reminiscent of experimental observations. The low field side mid-plane in particular is found to be locally more fluctuating and intermittent than the rest of the Scrape-Off-Layer (SOL). As a consequence of this asymmetry, radial turbulent transport, that represents 80 to 90% of the total radial flux, is strongly ballooned, with 75% of the flux flowing through LFS. The equilibrium of the edge plasma is impacted by this asymmetry through the existence of large amplitude asymmetric parallel flows as well as through the development of poloidally asymmetric radial decay lengths making it impossible to define a single SOL width.
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Philippe Ghendrih, et al.. 3D properties of edge turbulent transport in full-torus simulations and their impact on poloidal asymmetries. Contributions to Plasma Physics, 2014, 54 (4-6), pp.555-559. ⟨10.1002/ctpp.201410017⟩. ⟨hal-01053290⟩
Nils Tilton, Eric Serre, Denis Martinand, Richard M. Lueptow. A 3D pseudospectral algorithm for fluid flows with permeable walls. Application to filtration. Computers and Fluids, 2014, 93, pp.129-145. ⟨10.1016/j.compfluid.2014.01.003⟩. ⟨hal-01053339⟩ Plus de détails...
The present work proposes a Chebyshev-collocation Fourier-Galerkin pseudospectral method for simulating unsteady, three-dimensional, fluid flows in cylindrical geometries with pressure-driven flow through permeable boundaries. Such systems occur in diverse applications and are challenging to simulate due to an additional velocity-pressure coupling on the permeable walls through Darcy's law. The present work extends the projection method of Raspo et al. (2002) to assure Darcy's law is satisfied exactly. A multidomain solver allows the efficient treatment of open boundary conditions that necessitate permeability buffers and a sponge layer. The method is spectrally convergent, and we demonstrate that pressure-prediction is necessary to obtain second-order temporal accuracy. The ability of the method to simulate complicated physical systems is demonstrated by simulating subcritical and supercritical flows in rotating filtration in Taylor-Couette cells. For subcritical cases, numerical results show excellent agreement with analytical solutions. For supercritical cases, the numerical method accurately resolves convectively and absolutely unstable flows with traveling toroidal and helical vortical structures that are in good agreement with a local linear stability analysis and experimental observations.
Nils Tilton, Eric Serre, Denis Martinand, Richard M. Lueptow. A 3D pseudospectral algorithm for fluid flows with permeable walls. Application to filtration. Computers and Fluids, 2014, 93, pp.129-145. ⟨10.1016/j.compfluid.2014.01.003⟩. ⟨hal-01053339⟩
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Density regimes and heat flux deposition in the WEST shallow divertor configuration. Contributions to Plasma Physics, 2014, 54 (4-6), pp.378-382. ⟨10.1002/ctpp.201410026⟩. ⟨hal-01053281⟩ Plus de détails...
To support ITER divertor design, the WEST project on Tore Supra aims at studying high heat fluxes on tungsten monoblock during long pulses. In that persective, a particular attention is paid to simulate the edge plasma interaction with complex PFCs using the transport code SOLEDGE2D-EIRENE. The plasma response to a heating and puffing scenario is described as well as the so-called divertor density regimes, characterizing the operational domain of the WEST divertor. These results are compared for two different magnetic configurations: a semi-open double null divertor with the X-point away from the target plates and a shallow divertor configuration with the X-point close to the targets.
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Density regimes and heat flux deposition in the WEST shallow divertor configuration. Contributions to Plasma Physics, 2014, 54 (4-6), pp.378-382. ⟨10.1002/ctpp.201410026⟩. ⟨hal-01053281⟩
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich H. Busse. Geometry effects on the onset of rotating Rayleigh-Bénard convection in annuli. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2014, 89, pp.063013. ⟨hal-01087216⟩ Plus de détails...
Rayleigh-Bénard convection is investigated in rotating annular cavities at a moderate rotationrate (square root of the Taylor number) Omega= 60. The onset of convection is in the form of azimuthaltraveling waves that set in at the sidewalls and at values of the Rayleigh number significantly belowthe value of the onset of convection in an infinitely extended layer. When curvature effect becomessignificant, the waves traveling along the sidewalls have different critical Rayleigh numbers and com-plex Guinzburg-Landau equations are no longer applicable. The present study addresses the effectsof curvature and confinement on the onset of sidewall convection by using three-dimensional spectralsolutions of the Oberbeck-Boussinesq equations. Such solutions demonstrate that the curvature ofthe outer boundary promotes the onset of the wall mode, while the opposite curvature of the innerboundary tends to delay the onset of the wall mode. When radial confinement is increased the twoindependent traveling waves can interact and eventually merge to form a nearly steady pattern ofconvection.
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich H. Busse. Geometry effects on the onset of rotating Rayleigh-Bénard convection in annuli. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2014, 89, pp.063013. ⟨hal-01087216⟩
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
Alejandro Paredes, Hugo Bufferand, Guido Ciraolo, Frédéric Schwander, Eric Serre, et al.. A penalization technique to model plasma facing components in a tokamak with temperature variations. Journal of Computational Physics, 2014, 274, pp.283-298. ⟨hal-01087225⟩ Plus de détails...
To properly address turbulent transport in the edge plasma region of a tokamak, it is mandatory to describe the particle and heat outflow on wall components, using an accurate representation of the wall geometry. This is challenging for many plasma transport codes, which use a structured mesh with one coordinate aligned with magnetic surfaces. We propose here a penalization technique that allows modelingof particle and heat transport using such structured mesh, while also accounting for geometrically complex plasma-facing components. Solid obstacles are considered as particle and momentum sinks whereas ionic and electronic temperature gradients are imposed on both sides of the obstacles along the magnetic field direction using delta functions (Dirac). Solutions exhibit plasma velocities (M=1) and temperatures fluxes at the plasma–wall boundaries that match with boundary conditions usually implemented in fluid codes. Grid convergence and error estimates are found to be in agreement with theoretical results obtained for neutral fluid conservation equations. The capability of the penalization technique is illustrated by introducing the non-collisional plasma region expected by the kinetic theory in the immediate vicinity of the interface, that is impossible when considering fluid boundary conditions. Axisymmetric numerical simulations show the efficiency of the method to investigate the large-scale transport at the plasma edge including the separatrix and in realistic complex geometries while keeping a simple structured grid.
Alejandro Paredes, Hugo Bufferand, Guido Ciraolo, Frédéric Schwander, Eric Serre, et al.. A penalization technique to model plasma facing components in a tokamak with temperature variations. Journal of Computational Physics, 2014, 274, pp.283-298. ⟨hal-01087225⟩
Guillaume Fontaine, Sébastien Poncet, Eric Serre. Multidomain Extension of a Pseudospectral Algorithm for the Direct Simulation of Wall-Confined Rotating Flows. M. Azaiez, H. El Fekih, J.S. Hesthaven. Lecture Notes in Computational Science and Engineering, 95, Springer, pp.261 - 271, 2014, ⟨10.1007/978-3-319-01601-6_21⟩. ⟨hal-01098589⟩ Plus de détails...
In this work, we improve an existing pseudospectral algorithm, in order to extend its properties to a multidomain patching of a rotating cavity. Viscous rotating flows have been widely studied over the last decades, either on industrial or aca-demic approaches. Nevertheless, the range of Reynolds numbers reached in indus-trial devices implies very high resolutions of the spatial problem, which are clearly unreachable using a monodomain approach. Hence, we worked on the multido-main extension of the existing divergence-free Navier-Stokes solver with a Schur approach. The particularity of such an approach is that it does not require any sub-domain superposition: the value of a variable on the boundary between two adjacent subdomains is treated as a boundary condition of a local Helmholtz solver. This value is computed on a direct way via a so-called continuity influence matrix and the derivative jump of an homogeneous solution computed independently on each subdomain. Such a method is known to have both good scalability and accuracy. It has been validated on two well documented three-dimensional rotating flows.
Guillaume Fontaine, Sébastien Poncet, Eric Serre. Multidomain Extension of a Pseudospectral Algorithm for the Direct Simulation of Wall-Confined Rotating Flows. M. Azaiez, H. El Fekih, J.S. Hesthaven. Lecture Notes in Computational Science and Engineering, 95, Springer, pp.261 - 271, 2014, ⟨10.1007/978-3-319-01601-6_21⟩. ⟨hal-01098589⟩
Hugo Bufferand, Guido Ciraolo, Guilhem Dif-Pradalier, Philippe Ghendrih, Patrick Tamain, et al.. Magnetic geometry and particle source drive of supersonic divertor regimes. Plasma Physics and Controlled Fusion, 2014, 56 (122001), ⟨10.1088/0741-3335/56/12/122001⟩. ⟨hal-01225185⟩ Plus de détails...
We present a comprehensive picture of the mechanisms driving the transition from subsonic to supersonic flows in tokamak plasmas. We demonstrate that supersonic parallel flows into the divertor volume are ubiquitous at low density and governed by the divertor magnetic geometry. As the density is increased, subsonic divertor plasmas are recovered. On detachment, we show the change in particle source can also drive the transition to a supersonic regime. The comprehensive theoretical analysis is completed by simulations in ITER geometry. Such results are essential in assessing the divertor performance and when interpreting measurements and experimental evidence. The generation of large-scale flows in laboratory plasma is a highly non-linear problem. In a standard fashion it is considered that the flows remain subsonic away from the wall, the occurrence of supersonic flows being singular. We show here that the geometrical features of key configurations for fusion plasma can lead to supersonic flows.
Hugo Bufferand, Guido Ciraolo, Guilhem Dif-Pradalier, Philippe Ghendrih, Patrick Tamain, et al.. Magnetic geometry and particle source drive of supersonic divertor regimes. Plasma Physics and Controlled Fusion, 2014, 56 (122001), ⟨10.1088/0741-3335/56/12/122001⟩. ⟨hal-01225185⟩
Clothilde Colin, Patrick Tamain, Philippe Ghendrih, Frederic Schwander, Eric Serre. Impact of a Langmuir probe on turbulence measurements in the Scrape-Off-Layer of tokamaks. Contributions to Plasma Physics, 2014, 54 (4-6), pp.543-548. ⟨10.1002/ctpp.201410087⟩. ⟨hal-01019696⟩ Plus de détails...
An issue for Langmuir probe measurements of SOL turbulence concerns the impact of the probe itself on plasma transport. The aim of this paper is to investigate this issue with a synthetic reconstruction of Langmuir probe measurements by inserting a synthetic probe into a 2D fluid SOL turbulence code. The effect of a biased probe is analysed as a function of its size. It is shown that the probe creates a transport barrier whose effect is non-local and affects the current's circulation in the plasma. The plasma density is depleted by the presence of the probe as well as the electrostatic potential. A strong impact on turbulence can also be observed. Such observations imply that the probed turbulence can differ significantly from the probe-free turbulence
Clothilde Colin, Patrick Tamain, Philippe Ghendrih, Frederic Schwander, Eric Serre. Impact of a Langmuir probe on turbulence measurements in the Scrape-Off-Layer of tokamaks. Contributions to Plasma Physics, 2014, 54 (4-6), pp.543-548. ⟨10.1002/ctpp.201410087⟩. ⟨hal-01019696⟩
Alejandro Paredes, Eric Serre, Frédéric Schwander, Philippe Ghendrih, Patrick Tamain. Numerical fluid modelling of the plasma edge response to a 3D object and application to mach probe measurements. Contributions to Plasma Physics, 2014, 54 (4-6), pp.373-377. ⟨10.1002/ctpp.201410028⟩. ⟨hal-01050666⟩ Plus de détails...
The penalization method is used to model the interaction of 3D probe with an isothermal plasma. Density maps show that the region perturbed by the obstacle, is not restricted to its near neighbourhood, but can extend to the whole SOL. In the particular case of a probe, which is used to measure local plasma parameters, this impact can lead to violation of assumptions of locality of the perturbation usually used in determining Mach number from the imbalance in density on both sides of the probe.
Alejandro Paredes, Eric Serre, Frédéric Schwander, Philippe Ghendrih, Patrick Tamain. Numerical fluid modelling of the plasma edge response to a 3D object and application to mach probe measurements. Contributions to Plasma Physics, 2014, 54 (4-6), pp.373-377. ⟨10.1002/ctpp.201410028⟩. ⟨hal-01050666⟩
Guido Ciraolo, Hugo Bufferand, Philippe Ghendrih, Patrick Tamain, Jérome Bucalossi, et al.. Investigation of edge and SOL particle flux patterns in high density regimes using SOLEDGE2D-EIRENE code. Contributions to Plasma Physics, 2014, 54 (4-6), pp.432-436. ⟨10.1002/ctpp.201410018⟩. ⟨hal-01050505⟩ Plus de détails...
We present numerical simulations of plasma transport obtained with the SOLEDGE2D code coupled to the EIRENE Montecarlo code for neutrals. We consider a double null magnetic configuration in a WEST geometry. Density and temperatures parallel profiles in the SOL domain are presented as well as Mach profile. We detail how using the penalization technique we are able to model plasma transport up to the first wall having access to energy and particle fluxes on the entire chamber wall. Moreover, we present the computed 2D contour map of the plasma mach number and of the magnitude of the ionisation source term in the whole poloidal section, emphasizing how complex and realistic geometries can be handled thanks to the penalization technique.
Guido Ciraolo, Hugo Bufferand, Philippe Ghendrih, Patrick Tamain, Jérome Bucalossi, et al.. Investigation of edge and SOL particle flux patterns in high density regimes using SOLEDGE2D-EIRENE code. Contributions to Plasma Physics, 2014, 54 (4-6), pp.432-436. ⟨10.1002/ctpp.201410018⟩. ⟨hal-01050505⟩
Philippe Ghendrih, Thomas Auphan, B. Bensiali, Marco Bilanceri, K. Bodi, et al.. Divertor imbalance and divertor density regimes for ballooned cross-field turbulence. Journal of Nuclear Materials, 2013, 438, pp.S368-S371. ⟨10.1016/j.jnucmat.2013.01.070⟩. ⟨hal-00920748⟩ Plus de détails...
The ballooned nature of cross-field transport is shown to govern the steady state divertor imbalance of the energy flux leading to a factor 10 between the low field side and high field energy flux. An even stronger ratio is found for the divertor temperatures. Conversely the particle flux is expected to be a factor 10 larger on the high field side than on the low field side. The transition to detachment, close to divertor thermal collapse, exhibits several constraints to maintain steady state solutions. These constraints, related in particular to a large drop of the divertor density upon detachment, are shown to strongly correlate the pressure and particle flux variation along the field line and consequently the various loss channels. This delicate balance between different mechanisms is a possible understanding of the difficulty reported in detached plasma operation and simulation.
Philippe Ghendrih, Thomas Auphan, B. Bensiali, Marco Bilanceri, K. Bodi, et al.. Divertor imbalance and divertor density regimes for ballooned cross-field turbulence. Journal of Nuclear Materials, 2013, 438, pp.S368-S371. ⟨10.1016/j.jnucmat.2013.01.070⟩. ⟨hal-00920748⟩
A. Paredes, Hugo Bufferand, F. Schwander, G. Ciraolo, E. Serre, et al.. Penalization technique to model wall-component impact on heat and mass transport in the tokamak edge. Journal of Nuclear Materials, 2013, 438, pp.625-628. ⟨10.1016/j.jnucmat.2013.01.131⟩. ⟨hal-01101342⟩ Plus de détails...
The original and computationally efficient volume penalization technique Ref. [1], proposed for an isothermal plasma to recover the Bohm boundary condition at the plasma–obstacle interface, is extended to model 3D obstacles. It is then generalized to handle electron and ion temperatures in a 1D model. Results in 3D simulations show that the geometry of secondary limiter has an influence on the density and particle flux profiles, breaking its toroidal symmetry and introducing profile gaps of magnitude of 20%. On the other hand, the generalization of the penalization scheme to the non-isothermal case demands to deal with new Neumann conditions on the heat fluxes. Those boundary conditions require the introduction of new mask functions to ensure that the Bohm boundary condition remains satisfied.
A. Paredes, Hugo Bufferand, F. Schwander, G. Ciraolo, E. Serre, et al.. Penalization technique to model wall-component impact on heat and mass transport in the tokamak edge. Journal of Nuclear Materials, 2013, 438, pp.625-628. ⟨10.1016/j.jnucmat.2013.01.131⟩. ⟨hal-01101342⟩
Eric Serre, Mathieu Minguez, R. Pasquetti, Emmanuel Guilmineau, G.B. Deng, et al.. On simulating the turbulent flow around the Ahmed body: a french-german collaborative evaluation of LES and DES. Computers and Fluids, 2013, 78, pp.10-23. ⟨ujm-00860576⟩ Plus de détails...
The paper presents a comparative analysis of recent simulations, conducted in the framework of a French-German collaboration on LES of Complex Flows, for the so-called Ahmed body at Reynolds number 768000 and slant angle 25°. It provides a juxtaposition of results obtained with different eddy-resolving modeling approaches, i.e. two Large Eddy Simulations (LES) on body-fitted curvilinear grids, a stabilized spectral method and a Detachted Eddy Simulation (DES) on an unstructured grid. The paper presents a comprehensive data base including both instantaneous and statistical data. A central achievement is the comparative assessment of the different approaches with an appreciation of the respective advantages and disadvantages of the various methods. In particular, issues on computational cost and ease of implementation are addressed in addition to the quality of results.
Eric Serre, Mathieu Minguez, R. Pasquetti, Emmanuel Guilmineau, G.B. Deng, et al.. On simulating the turbulent flow around the Ahmed body: a french-german collaborative evaluation of LES and DES. Computers and Fluids, 2013, 78, pp.10-23. ⟨ujm-00860576⟩
Hugo Bufferand, B. Bensiali, J. Bucalossi, G. Ciraolo, P. Genesio, et al.. Near wall plasma simulation using penalization technique with the transport code Soledge2D-EIRENE. Journal of Nuclear Materials, 2013, 438, pp.445-448. ⟨10.1016/j.jnucmat.2013.01.090⟩. ⟨hal-01101345⟩ Plus de détails...
In order to model plasma interaction with full complexity of the geometry of PFCs, an immersed method to impose boundary conditions has been implemented in the transport code SolEdge2D. This penalization technique has proven to properly recover Bohm boundary conditions, including supersonic solutions at the sheath entrance. The role of the ionization source has been taken into account by coupling SolEdge2D with the 3D kinetic neutral code Eirene. Density regimes are properly recovered and major differences between core located and divertor located ionization source regimes are emphasized. One also presents main chamber wall recycling regime simulations that can now be addressed with simulations of the entire edge plasma up to the wall.
Hugo Bufferand, B. Bensiali, J. Bucalossi, G. Ciraolo, P. Genesio, et al.. Near wall plasma simulation using penalization technique with the transport code Soledge2D-EIRENE. Journal of Nuclear Materials, 2013, 438, pp.445-448. ⟨10.1016/j.jnucmat.2013.01.090⟩. ⟨hal-01101345⟩
Eric Eric Serre, M. Minguez, R. Pasquetti, Emmanuel Guilmineau, G.B. Deng, et al.. On simulating the turbulent flow around the Ahmed body: a French-German collaborative evaluation of LES and DES. Computers and Fluids, 2013, 78, pp.10-23. ⟨10.1016/j.compfluid.2011.05.017⟩. ⟨hal-01101350⟩ Plus de détails...
The paper presents a comparative analysis of recent simulations, conducted in the framework of a French-German collaboration on LES of Complex Flows, for the so-called Ahmed body at Reynolds number 768000 and slant angle 25°. It provides a juxtaposition of results obtained with different eddy-resolving modeling approaches, i.e. two Large Eddy Simulations (LES) on body-fitted curvilinear grids, a stabilized spectral method and a Detachted Eddy Simulation (DES) on an unstructured grid. The paper presents a comprehensive data base including both instantaneous and statistical data. A central achievement is the comparative assessment of the different approaches with an appreciation of the respective advantages and disadvantages of the various methods. In particular, issues on computational cost and ease of implementation are addressed in addition to the quality of results.
Eric Eric Serre, M. Minguez, R. Pasquetti, Emmanuel Guilmineau, G.B. Deng, et al.. On simulating the turbulent flow around the Ahmed body: a French-German collaborative evaluation of LES and DES. Computers and Fluids, 2013, 78, pp.10-23. ⟨10.1016/j.compfluid.2011.05.017⟩. ⟨hal-01101350⟩
Eric Serre, Hugo Bufferand, A. Paredes, Frédéric Schwander, Guido Ciraolo, et al.. Numerical modeling of the impact of geometry and wall components on transport in the tokamak edge. Contributions to Plasma Physics, 2012, 52 (5-6), pp.401-405. ⟨10.1002/ctpp.201210023⟩. ⟨hal-00848473⟩ Plus de détails...
The SOLEDGE suite of codes has been specially designed to model the transition region from the hot core plasma to the first wall of tokamak, through the Last Closed Flux Surface (LCFS). It is designed to model electrostatic fluid turbulence for an isothermal plasma or for a plasma with temperature variations. Dedicated discretization algorithms have been implemented to handle equations for ion density, electron/ion temperatures and parallel momentum, both for the realistic cross-section of a diverted tokamak and for a three-dimensional cylindrical annulus. The efficient penalization method introduced in Ref. [5] has been implemented, allowing straightforward handling of solid obstacles by treating them as sink regions corresponding to strong plasma recombination in the solid state material. The SOLEDGE capability is exemplified here by simulating two equilibria: (i) a 3D cylindrical annulus and (ii) the cross-section of a diverted tokamak. In the annulus, the analysis of the impact of a secondary discrete limiter shows that the toroidal symmetry usually assumed for density and Mach profiles is broken. The density exhibits significant variations in the toroidal direction that extend over a large region of the scrape-off layer where magnetic field lines are connected to a secondary limiter. In the diverted geometry, computations show a transition from subsonic to supersonic flow in the vicinity of the X-point that is related to the location of particle sources and sinks between the edge connected region and the divertor region.
Eric Serre, Hugo Bufferand, A. Paredes, Frédéric Schwander, Guido Ciraolo, et al.. Numerical modeling of the impact of geometry and wall components on transport in the tokamak edge. Contributions to Plasma Physics, 2012, 52 (5-6), pp.401-405. ⟨10.1002/ctpp.201210023⟩. ⟨hal-00848473⟩
Philippe Meliga, Gregory Pujals, Eric Serre. Sensitivity of 2-D turbulent flow past a D-shaped cylinder using global stability. Physics of Fluids, 2012, 24, pp.061701. ⟨10.1063/1.4724211⟩. ⟨hal-01061797⟩ Plus de détails...
We use adjoint-based gradients to analyze the sensitivity of turbulent wake past a D-shaped cylinder at Re = 13000. We assess the ability of a much smaller control cylinder in altering the shedding frequency, as predicted by the eigenfrequency of the most unstable global mode to the mean flow. This allows performing beforehand identification of the sensitive regions, i.e., without computing the actually controlled states. Our results obtained in the frame of 2-D, unsteady Reynolds-averaged Navier-Stokes compare favorably with experimental data reported by Parezanović and Cadot [J. Fluid Mech.693, 115 (2012)] and suggest that the control cylinder acts primarily through a local modification of the mean flow profiles.
Philippe Meliga, Gregory Pujals, Eric Serre. Sensitivity of 2-D turbulent flow past a D-shaped cylinder using global stability. Physics of Fluids, 2012, 24, pp.061701. ⟨10.1063/1.4724211⟩. ⟨hal-01061797⟩
Ouafa Bouloumou, Eric Serre, Patrick Bontoux, J. Fröhlich. A 3D pseudo-spectral low Mach-number solver for buoyancy driven flows with large temperature differences. Computers and Fluids, 2012, 66, pp.107-120. ⟨10.1016/j.compfluid.2012.05.014⟩. ⟨hal-00834130⟩ Plus de détails...
A three-dimensional spectral method based on a Chebyshev/Chebyshev/Fourier discretization is proposed to integrate the Navier-Stokes equations for natural convection flow with large temperature differences under the low Mach-number approximation. The generalized Stokes problem arising from the time discretization by a second-order semi-implicit scheme is solved by a preconditioned iterative Uzawa algorithm. The spectrally convergent algorithm is validated on well-documented Boussinesq and non-Boussinesq benchmarks. Finally, non-Boussineq convection is investigated in a tall differentially heated cavity of aspect ratio 8 with one homogeneous direction. The technique is shown to be efficient in terms of computing performances and accuracy. The study brings new stability results evidencing 3D effects compared to both Boussinesq convection and former two-dimensional non-Boussinesq solutions. In particular, for Ra ⩾ 105 two-dimensional solutions are shown to be unstable with respect to three-dimensional perturbations. A Görtler-type instability grows in the region of the curved streamlines at both ends of the cavity and gives rise to 3D steady and oscillatory solutions. At higher Rayleigh numbers, these vortices eventually interact with a boundary layer instability leading to complex dynamics with multiple steady and unsteady stable solutions.
Ouafa Bouloumou, Eric Serre, Patrick Bontoux, J. Fröhlich. A 3D pseudo-spectral low Mach-number solver for buoyancy driven flows with large temperature differences. Computers and Fluids, 2012, 66, pp.107-120. ⟨10.1016/j.compfluid.2012.05.014⟩. ⟨hal-00834130⟩
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Incorporating Darcy's law for pure solvent flow through porous tubes: Asymptotic solution and numerical simulations. AIChE Journal, 2012, 58 (7), pp.2030-2044. ⟨10.1002/aic.13823⟩. ⟨hal-01032148⟩ Plus de détails...
A generalized solution for pressure-driven, incompressible, Newtonian flow in a porous tubular membrane is challenging due to the coupling between the transmembrane pressure and velocity. To date, all analytical solutions require simplifications such as neglecting the coupling between the transmembrane pressure and velocity, assuming the form of the velocity fields, or expanding in powers of parameters involving the tube length. Moreover, previous solutions have not been validated with comparison to direct numerical simulation (DNS). We comprehensively revisit the problem to present a robust analytical solution incorporating Darcy's law on the membrane. We make no assumptions about the tube length or form of the velocity fields. The analytic solution is validated with detailed comparison to DNSs, including cases of axial flow exhaustion and cross flow reversal. We explore the validity of typical assumptions used in modeling porous tube flow and present a solution for porous channels in Supporting Information.
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Incorporating Darcy's law for pure solvent flow through porous tubes: Asymptotic solution and numerical simulations. AIChE Journal, 2012, 58 (7), pp.2030-2044. ⟨10.1002/aic.13823⟩. ⟨hal-01032148⟩
Matthieu Minguez, Christophe Brun, Richard Pasquetti, Eric Serre. Experimental and high-order LES analysis of the flow in near-wall region of a square cylinder. International Journal of Heat and Fluid Flow, Elsevier, 2011, 32 (3), pp.558-566. ⟨10.1016/j.ijheatfluidflow.2011.03.009⟩. ⟨hal-01299962⟩ Plus de détails...
A coupled experimental/numerical analysis of turbulent flow past a square cylinder is performed at the ERCOFTAC Reynolds number Re = U∞D/ν = 21,400, where U∞ is the inflow velocity and D the cylinder height. Complementary Laser Doppler Velocimetry (LDV) and high-order large-eddy simulations (LES) approaches, based on a spectral vanishing technique (SVV-LES), provide a comprehensive data base including both instantaneous data and post-processed statistics. Beyond these results, an achievement of the paper is to investigate the coherent structures developing on the sides and in the wake of the cylinder with a special focus on the flow features in the near-wall region. The flow is found to separate at the leading edge of the cylinder with the occurence of three-dimensional Kelvin–Helmholtz (KH) pairings localized in the separating shear layer. The interaction between these KH vortical structures and Von Kármán vortex shedding (VK) in the near wake is discussed based on both visualisations and frequency analysis. In particular, signatures of VK and KH vortical structures are found on velocity time samples.
Matthieu Minguez, Christophe Brun, Richard Pasquetti, Eric Serre. Experimental and high-order LES analysis of the flow in near-wall region of a square cylinder. International Journal of Heat and Fluid Flow, Elsevier, 2011, 32 (3), pp.558-566. ⟨10.1016/j.ijheatfluidflow.2011.03.009⟩. ⟨hal-01299962⟩
Journal: International Journal of Heat and Fluid Flow
Eric Serre, M. Minguez, R., Pasquetti, G.B. Deng, M. Kornhass, et al.. On simulating the turbulent flow around the Ahmed body : A French-German collaborative evaluation of LES and DES. Computers and Fluids, 2011. ⟨hal-01145131⟩ Plus de détails...
Eric Serre, M. Minguez, R., Pasquetti, G.B. Deng, M. Kornhass, et al.. On simulating the turbulent flow around the Ahmed body : A French-German collaborative evaluation of LES and DES. Computers and Fluids, 2011. ⟨hal-01145131⟩
Hugo Bufferand, Guido Ciraolo, Livia Isoardi, Guillaume Chiavassa, Frédéric Schwander, et al.. Applications of SOLEDGE-2D code to complex SOL configurations and analysis of Mach probe measurements. Journal of Nuclear Materials, 2011, 415 (1), pp.S589-S592. ⟨10.1016/j.jnucmat.2010.11.037⟩. ⟨hal-00848483⟩ Plus de détails...
A series of experiments dedicated to the determination of the ballooning nature of the edge and SOL transport has been achieved on Tore Supra and , proposing a quantitative characterization of the radial flux that enters the SOL. The aim of this paper is to back up the interpretation of these probe flow measurements making use of SOLEDGE-2D code. In particular, this fluid code allows one to study density and parallel momentum transport in a 2D geometry including edge and SOL region. Moreover, thanks to an appropriate numerical technique recently proposed and , SOLEDGE-2D code is also able to deal with a complex geometry of plasma facing components including main and secondary limiters.
Hugo Bufferand, Guido Ciraolo, Livia Isoardi, Guillaume Chiavassa, Frédéric Schwander, et al.. Applications of SOLEDGE-2D code to complex SOL configurations and analysis of Mach probe measurements. Journal of Nuclear Materials, 2011, 415 (1), pp.S589-S592. ⟨10.1016/j.jnucmat.2010.11.037⟩. ⟨hal-00848483⟩
Hugo Bufferand, Guido Ciraolo, Livia Isoardi, Guillaume Chiavassa, Frédéric Schwander, et al.. Applications of SOLEDGE-2D code to complex SOL configurations and analysis of Mach probe measurements. Journal of Nuclear Materials, 2011, 415 (1), pp.S589-S592. ⟨10.1016/j.jnucmat.2010.11.037⟩. ⟨hal-00848483⟩ Plus de détails...
A series of experiments dedicated to the determination of the ballooning nature of the edge and SOL transport has been achieved on Tore Supra and , proposing a quantitative characterization of the radial flux that enters the SOL. The aim of this paper is to back up the interpretation of these probe flow measurements making use of SOLEDGE-2D code. In particular, this fluid code allows one to study density and parallel momentum transport in a 2D geometry including edge and SOL region. Moreover, thanks to an appropriate numerical technique recently proposed and , SOLEDGE-2D code is also able to deal with a complex geometry of plasma facing components including main and secondary limiters.
Hugo Bufferand, Guido Ciraolo, Livia Isoardi, Guillaume Chiavassa, Frédéric Schwander, et al.. Applications of SOLEDGE-2D code to complex SOL configurations and analysis of Mach probe measurements. Journal of Nuclear Materials, 2011, 415 (1), pp.S589-S592. ⟨10.1016/j.jnucmat.2010.11.037⟩. ⟨hal-00848483⟩
Frédéric Schwander, Guillaume Chiavassa, Guido Ciraolo, Philippe Ghendrih, Livia Isoardi, et al.. Parallel shear flow instability in the tokamak edge. Journal of Nuclear Materials, 2011, 415 (1), pp.S601-S604. ⟨10.1016/j.jnucmat.2010.10.073⟩. ⟨hal-00848536⟩ Plus de détails...
The transition between the core and scrape-off layer of a tokamak corresponds to a marked momentum shear layer, owing to sheath acceleration on limiters which drives near-sonic flows along the plasma magnetic field in the scrape-off layer, and a parallel shear flow instability can possibly be triggered. The possibility of this instability driven by the velocity gradient is investigated numerically, using a minimum model of particle and parallel momentum transport in the edge of a tokamak, in a computational domain modelling a limiter plasma with background turbulence modelled as an effective diffusion. It is found that unstable regions can exist in the vicinity of a limiter, in agreement with experimental findings, when momentum radial transport - and therefore coupling between SOL and core flows - is sufficiently weak. Instability is reinforced by core rotation, and is found to be maximum downstream of the limiter (with respect to the core plasma flow).
Frédéric Schwander, Guillaume Chiavassa, Guido Ciraolo, Philippe Ghendrih, Livia Isoardi, et al.. Parallel shear flow instability in the tokamak edge. Journal of Nuclear Materials, 2011, 415 (1), pp.S601-S604. ⟨10.1016/j.jnucmat.2010.10.073⟩. ⟨hal-00848536⟩
Guilhem Dif-Pradalier, J Gunn, Guido Ciraolo, C S Chang, Guillaume Chiavassa, et al.. The Mistral base case to validate kinetic and fluid turbulence transport codes of the edge and SOL plasmas. Journal of Nuclear Materials, 2011, 415, ⟨10.1016/j.jnucmat.2010.12.035⟩. ⟨cea-01468372⟩ Plus de détails...
Experimental data from the Tore Supra experiments are extrapolated in the SOL and edge to investigate the Kelvin–Helmholtz instability. The linear analysis indicates that a large part of the SOL is rather unstable. The effort is part of the setup of the Mistral base case that is organised to validate the codes and address new issues on turbulent edges, including the comparison of kinetic and fluid modelling in the edge plasma.
Guilhem Dif-Pradalier, J Gunn, Guido Ciraolo, C S Chang, Guillaume Chiavassa, et al.. The Mistral base case to validate kinetic and fluid turbulence transport codes of the edge and SOL plasmas. Journal of Nuclear Materials, 2011, 415, ⟨10.1016/j.jnucmat.2010.12.035⟩. ⟨cea-01468372⟩
Livia Isoardi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, Frédéric Schwander, et al.. 2D modelling of electron and ion temperature in the plasma edge and SOL. Journal of Nuclear Materials, 2011, 415 (1), pp.S574-S578. ⟨10.1016/j.jnucmat.2010.12.318⟩. ⟨hal-00848528⟩ Plus de détails...
We are interested here in modelling the electron and ion temperature fields, Te and Ti respectively, in order to understand the main trends that govern the ratio Ti/Te that is being better documented in the SOL with RFA probes and . The experimental evidence gathered from several devices indicates that this temperature ratio significantly exceeds unity in most data sets that have been analysed, including measurements in the SOL of limiter devices like Tore Supra. Several issues of interest have been addressed with this version of the SOLEDGE-2D code. First, we have analysed the width of the SOL heat channels to the wall components and compared these values to analytical expressions. The key control mechanism of the width of the SOL heat channel is given by a balance between the sheath boundary conditions and the transverse transport. More advanced simulations address the interplay between the edge and SOL plasma allowing one to recover regimes with Ti/Te > 1.
Livia Isoardi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, Frédéric Schwander, et al.. 2D modelling of electron and ion temperature in the plasma edge and SOL. Journal of Nuclear Materials, 2011, 415 (1), pp.S574-S578. ⟨10.1016/j.jnucmat.2010.12.318⟩. ⟨hal-00848528⟩
Philippe Ghendrih, K. Bodi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, et al.. Transition to supersonic flows in the edge plasma. Plasma Physics and Controlled Fusion, 2011, 53 (5), pp.054019. ⟨10.1088/0741-3335/53/5/054019⟩. ⟨hal-00848545⟩ Plus de détails...
With a proper choice of a single dimensionless control parameter one describes the transition between subsonic and supersonic flows as a bifurcation. The bifurcation point is characterized by specific properties of the control parameter: the control parameter has a vanishing derivative in space and takes the maximum possible value equal to 1. This method is then applied to the sheath plasma with constant temperatures, allowing one to recover the Bohm boundary condition as well as the location of the point where the bifurcation takes place. This analysis is extended to fronts, rarefaction waves and divertor plasmas. Two cases are found, those where departure from quasineutrality is mandatory to generate a maximum in the variation of the control parameter (sheath and fronts) and those where the physics of the quasineutral plasma can generate such a maximum (rarefaction waves and supersonic flow in divertors). The conditions that are required to recover the Bohm condition, when modelling the wall using the penalization technique, are also addressed and generalized.
Philippe Ghendrih, K. Bodi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, et al.. Transition to supersonic flows in the edge plasma. Plasma Physics and Controlled Fusion, 2011, 53 (5), pp.054019. ⟨10.1088/0741-3335/53/5/054019⟩. ⟨hal-00848545⟩
B. Viaud, Eric Serre, Jean-Marc Chomaz. Transition to turbulence through steep global-modes cascade in an open rotating cavity. Journal of Fluid Mechanics, 2011, 688, pp.493-506. ⟨10.1017/jfm.2011.393⟩. ⟨hal-00998000⟩ Plus de détails...
B. Viaud, Eric Serre, Jean-Marc Chomaz. Transition to turbulence through steep global-modes cascade in an open rotating cavity. Journal of Fluid Mechanics, 2011, 688, pp.493-506. ⟨10.1017/jfm.2011.393⟩. ⟨hal-00998000⟩
Matthieu Minguez, Christophe Brun, Richard Pasquetti, Eric Serre. Experimental and high-order LES analysis of the flow in near-wall region of a square cylinder. International Journal of Heat and Fluid Flow, 2011, 32 (3), pp.558-566. ⟨10.1016/j.ijheatfluidflow.2011.03.009⟩. ⟨hal-01299962⟩ Plus de détails...
A coupled experimental/numerical analysis of turbulent flow past a square cylinder is performed at the ERCOFTAC Reynolds number Re = U∞D/ν = 21,400, where U∞ is the inflow velocity and D the cylinder height. Complementary Laser Doppler Velocimetry (LDV) and high-order large-eddy simulations (LES) approaches, based on a spectral vanishing technique (SVV-LES), provide a comprehensive data base including both instantaneous data and post-processed statistics. Beyond these results, an achievement of the paper is to investigate the coherent structures developing on the sides and in the wake of the cylinder with a special focus on the flow features in the near-wall region. The flow is found to separate at the leading edge of the cylinder with the occurence of three-dimensional Kelvin–Helmholtz (KH) pairings localized in the separating shear layer. The interaction between these KH vortical structures and Von Kármán vortex shedding (VK) in the near wake is discussed based on both visualisations and frequency analysis. In particular, signatures of VK and KH vortical structures are found on velocity time samples.
Matthieu Minguez, Christophe Brun, Richard Pasquetti, Eric Serre. Experimental and high-order LES analysis of the flow in near-wall region of a square cylinder. International Journal of Heat and Fluid Flow, 2011, 32 (3), pp.558-566. ⟨10.1016/j.ijheatfluidflow.2011.03.009⟩. ⟨hal-01299962⟩
Journal: International Journal of Heat and Fluid Flow
A. Paredes, Eric Serre, Livia Isoardi, Guillaume Chiavassa, Guido Ciraolo, et al.. Boundary conditions at the limiter surface obtained in the modelling of plasma wall interaction with a penalization technique. Journal of Nuclear Materials, 2011, 415 (1), pp.S579-S583. ⟨10.1016/j.jnucmat.2010.12.247⟩. ⟨hal-00848532⟩ Plus de détails...
Isoardi et al. [1] recently proposed a penalization technique to model solid plasma facing components that treats a solid obstacle as a sink region corresponding to the strong plasma recombination in the solid state material. A major advantage of this approach is that it produces a system that can be solved in an obstacle free domain, thus allowing the use of powerful numerical algorithms. Such a technique implemented in a minimal transport model for ionic density and parallel momentum appeared to exhibit a Mach-1 transition at the boundary layer between the plasma presheath and the limiter region. In this paper, we reconsider this result by analysing the physics of detached plasmas that are governed both by strong recombination and plasma pressure decrease, as imposed by the penalization technique within the limiter region. The analysis provides a unique control parameter A=Γcsmi/ΠA=Γcsmi/Π (Γ being the parallel particles flux, cs the sound speed, mi the ionic mass and Π the total plasma pressure) that allows one to understand the results of the penalization technique for the Mach-1 transition.
A. Paredes, Eric Serre, Livia Isoardi, Guillaume Chiavassa, Guido Ciraolo, et al.. Boundary conditions at the limiter surface obtained in the modelling of plasma wall interaction with a penalization technique. Journal of Nuclear Materials, 2011, 415 (1), pp.S579-S583. ⟨10.1016/j.jnucmat.2010.12.247⟩. ⟨hal-00848532⟩
Guillaume Chiavassa, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Hervé Guillard, et al.. Parallel expansion of density bursts. Journal of Nuclear Materials, 2011, 415 (1), pp.S613-S616. ⟨10.1016/j.jnucmat.2010.10.086⟩. ⟨hal-00848522⟩ Plus de détails...
Evidence of poloidally localized cross-field transport in experiments and theoretical analysis of turbulence transport governs the onset of parallel transport towards equilibrium. When cross-field transport appears in bursts, both for ELM relaxation events and microturbulence, the parallel transport of particles is shown to generate fronts that propagate with supersonic velocities. It is shown that after a short transient the density structure is no longer monotonic and that the two fronts (one co, the other counter the magnetic field) are independent. Furthermore, the time trace of the particle flux at a given location is characterized by a sharp rise followed by a longer time scale relaxation. Comparing the time delay and magnitude of the density burst at two locations allows to estimate the magnitude and the location of the generation of the front.
Guillaume Chiavassa, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Hervé Guillard, et al.. Parallel expansion of density bursts. Journal of Nuclear Materials, 2011, 415 (1), pp.S613-S616. ⟨10.1016/j.jnucmat.2010.10.086⟩. ⟨hal-00848522⟩
E. Plaut, Y. Lebranchu, M. Jenny, Eric Serre. Structure and stability of annular sheared channel flows: effects of confinement, curvature and inertial forces - waves. The European Physical Journal B: Condensed Matter and Complex Systems, 2011, 79 (1), pp.35-46. ⟨10.1140/epjb/e2010-10572-3⟩. ⟨hal-01023235⟩ Plus de détails...
The structure and stability of the flows in an annular channel sheared by a rotating lid are investigated experimentally, theoretically and numerically. The channel has a square section, and a small curvature parameter: the ratio Γ of the inter-radii to the mean radius is 9.5%. The sidewalls and the bottom of the channel are integral and can rotate independently of the lid, permitting pure shear, co-rotation and counter-rotation cases. The basic flows obtained at small shear are characterized. In the absence of co-rotation, the centrifugal force linked with the curvature of the system plays an important role, whereas, when co-rotation is fast, the Coriolis force dominates. These basic flows undergo some instabilities when the shear is increased. These instabilities lead to supercritical traveling waves in the pure shear and co-rotation cases, but to weak turbulence in the counter-rotation case. The Reynolds number for the onset of instabilities, constructed with the velocity difference between the lid and bottom at mid-radius, and the height of the channel, increases from 1000 in the counter-rotation case to 1260 in the pure shear case and higher and higher values when co-rotation increases, i.e., when the Coriolis effect increases. The relevance of uni-dimensional Ginzburg-Landau models to describe the dynamics of the waves is studied. The domain of validity of these models turns out to be quite narrow.
E. Plaut, Y. Lebranchu, M. Jenny, Eric Serre. Structure and stability of annular sheared channel flows: effects of confinement, curvature and inertial forces - waves. The European Physical Journal B: Condensed Matter and Complex Systems, 2011, 79 (1), pp.35-46. ⟨10.1140/epjb/e2010-10572-3⟩. ⟨hal-01023235⟩
Journal: The European Physical Journal B: Condensed Matter and Complex Systems
Brian Launder, Sébastien Poncet, Eric Serre. Laminar, transitional, and turbulent flows in rotor-stator cavities. Annual Review of Fluid Mechanics, 2010, 42 (1), pp.229-248. ⟨10.1146/annurev-fluid-121108-145514⟩. ⟨hal-00678846⟩ Plus de détails...
This article reviews the range of flows that may be created within thin cylindrical or annular cavities due to the rotation of one of the confining disks. At low Reynolds numbers, the rotation gives rise to an axisymmetric, radially outward motion near the rotor with a return flow along the stationary disk. As the Reynolds number is raised, this base flow gives way to a shear flow populated by discrete vortices, whether of cylindrical or spiral form, near both the rotating and stationary disks. At Reynolds numbers high enough for turbulent flow to occur, in the twentieth century both experimental and computational studies treated the flow as axisymmetric and steady. Recent research has shown, however, that complex organized structures also persist in the turbulent regime.
Brian Launder, Sébastien Poncet, Eric Serre. Laminar, transitional, and turbulent flows in rotor-stator cavities. Annual Review of Fluid Mechanics, 2010, 42 (1), pp.229-248. ⟨10.1146/annurev-fluid-121108-145514⟩. ⟨hal-00678846⟩
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Pressure-driven radial flow in a Taylor-Couette cell. Journal of Fluid Mechanics, 2010, 660, pp.527-537. ⟨10.1017/S0022112010003228⟩. ⟨hal-01024690⟩ Plus de détails...
A generalized solution for pressure-driven flow through a permeable rotating inner cylinder in an impermeable concentric outer cylinder, a situation used commercially in rotating filtration, is challenging due to the interdependence between the pressure drop in the axial direction and that across the permeable inner cylinder. Most previous approaches required either an imposed radial velocity at the inner cylinder or radial throughflow with both the inner and outer cylinders being permeable. We provide an analytical solution for rotating Couette-Poiseuille flow with Darcy's law at the inner cylinder by using a small parameter related to the permeability of the inner cylinder. The theory works for suction, injection and even combined suction/injection, when the axial pressure drop in the annulus is such that the transmembrane pressure difference reverses sign along the axial extent of the system. Corresponding numerical simulations for finite-length systems match the theory very well.
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Pressure-driven radial flow in a Taylor-Couette cell. Journal of Fluid Mechanics, 2010, 660, pp.527-537. ⟨10.1017/S0022112010003228⟩. ⟨hal-01024690⟩
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, 2009, 390-391, pp.388-391. ⟨10.1016/j.jnucmat.2009.01.088⟩. ⟨hal-00848559⟩ Plus de détails...
The transition region between closed and open magnetic flux surfaces plays a crucial role for tokamak performances. Appropriate understanding of the edge region remains a major challenge owing to several open issues as momentum transport, turbulence overshoot or neutral penetration. We consider here a transport model system to investigate the propagation of parallel momentum from the SOL into the core plasma and vice-versa. The numerical results show that for small values of the radial diffusion coefficient, the density profile decays exponentially from the core to the SOL as predicted by 1D analytical solution. A spreading of the parallel momentum from the SOL to the core is observed, with the presence of non-zero velocities also in the regions far from the SOL. The effect of an imposed rotation of the core plasma is investigated as well as the dynamics of an overdensity imposed in the core plasma.
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, 2009, 390-391, pp.388-391. ⟨10.1016/j.jnucmat.2009.01.088⟩. ⟨hal-00848559⟩
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, 2009, 390-391, pp.388-391. ⟨10.1016/j.jnucmat.2009.01.088⟩. ⟨hal-00848559⟩ Plus de détails...
The transition region between closed and open magnetic flux surfaces plays a crucial role for tokamak performances. Appropriate understanding of the edge region remains a major challenge owing to several open issues as momentum transport, turbulence overshoot or neutral penetration. We consider here a transport model system to investigate the propagation of parallel momentum from the SOL into the core plasma and vice-versa. The numerical results show that for small values of the radial diffusion coefficient, the density profile decays exponentially from the core to the SOL as predicted by 1D analytical solution. A spreading of the parallel momentum from the SOL to the core is observed, with the presence of non-zero velocities also in the regions far from the SOL. The effect of an imposed rotation of the core plasma is investigated as well as the dynamics of an overdensity imposed in the core plasma.
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, 2009, 390-391, pp.388-391. ⟨10.1016/j.jnucmat.2009.01.088⟩. ⟨hal-00848559⟩
Emilia Crespo del Arco, José Sanchez Alvarez, Eric Serre, A. de La Torre, Javier Burguete. Numerical and experimental study of the time dependent states and the slow dynamics in a von Karman swirling flow. Geophysical and Astrophysical Fluid Dynamics, 2008, 103 (2), pp.1-15. ⟨hal-01023287⟩ Plus de détails...
Emilia Crespo del Arco, José Sanchez Alvarez, Eric Serre, A. de La Torre, Javier Burguete. Numerical and experimental study of the time dependent states and the slow dynamics in a von Karman swirling flow. Geophysical and Astrophysical Fluid Dynamics, 2008, 103 (2), pp.1-15. ⟨hal-01023287⟩
Journal: Geophysical and Astrophysical Fluid Dynamics
Eric Serre, Michael Sprague, Richard M. Lueptow. Stability of Taylor-Couette flow with radial throughflow. Physics of Fluids, 2008, 20 (3), pp.034106. ⟨hal-01023284⟩ Plus de détails...
Eric Serre, Michael Sprague, Richard M. Lueptow. Stability of Taylor-Couette flow with radial throughflow. Physics of Fluids, 2008, 20 (3), pp.034106. ⟨hal-01023284⟩
Eric Serre, Mathieu Minguez, Richard Pasquetti. Spectral vanishing viscosity stabilized LES of the Ahmed body turbulent wake. Communications in Computational Physics, 2008, 5 (2-4), pp.635-648. ⟨hal-01023286⟩ Plus de détails...
Eric Serre, Mathieu Minguez, Richard Pasquetti. Spectral vanishing viscosity stabilized LES of the Ahmed body turbulent wake. Communications in Computational Physics, 2008, 5 (2-4), pp.635-648. ⟨hal-01023286⟩
B. Viaud, E. Serre, Jean-Marc Chomaz. The elephant mode between two rotating disks. Journal of Fluid Mechanics, 2008, 598 (mars), pp.451-464. ⟨10.1017/s0022112007009962⟩. ⟨hal-01022811⟩ Plus de détails...
B. Viaud, E. Serre, Jean-Marc Chomaz. The elephant mode between two rotating disks. Journal of Fluid Mechanics, 2008, 598 (mars), pp.451-464. ⟨10.1017/s0022112007009962⟩. ⟨hal-01022811⟩
Bertrand Viaud, Eric Serre, Jean-Marc Chomaz. Elephant mode sitting on a rotating disk in an annulus. Journal of Fluid Mechanics, 2008, 598, pp.451-464. ⟨hal-01023281⟩ Plus de détails...
Bertrand Viaud, Eric Serre, Jean-Marc Chomaz. Elephant mode sitting on a rotating disk in an annulus. Journal of Fluid Mechanics, 2008, 598, pp.451-464. ⟨hal-01023281⟩
Richard Pasquetti, Eric Séverac, Eric Serre, Patrick Bontoux, Michael Schaefer. From stratified wake to rotor-stator flows by a SVV-LES method. Theoretical and Computational Fluid Dynamics, 2008, 22 (3-4), pp.261-273. ⟨hal-01023280⟩ Plus de détails...
Richard Pasquetti, Eric Séverac, Eric Serre, Patrick Bontoux, Michael Schaefer. From stratified wake to rotor-stator flows by a SVV-LES method. Theoretical and Computational Fluid Dynamics, 2008, 22 (3-4), pp.261-273. ⟨hal-01023280⟩
Journal: Theoretical and Computational Fluid Dynamics
Margarete Domingues, Ingmar Broemstrup, Kai Schneider, Marie Farge, Benjamin Kadoch. Coherent vortex extraction in 3D homogeneous isotropic turbulence using orthogonal wavelets. ESAIM: Proceedings, 2007, 16, pp.164-180. ⟨10.1051/proc:2007005⟩. ⟨hal-02535148⟩ Plus de détails...
Margarete Domingues, Ingmar Broemstrup, Kai Schneider, Marie Farge, Benjamin Kadoch. Coherent vortex extraction in 3D homogeneous isotropic turbulence using orthogonal wavelets. ESAIM: Proceedings, 2007, 16, pp.164-180. ⟨10.1051/proc:2007005⟩. ⟨hal-02535148⟩
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich H. Busse. Square patterns in rotating Rayleigh-Bénard convection. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2005, 72, pp.036307. ⟨hal-01023277⟩ Plus de détails...
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich H. Busse. Square patterns in rotating Rayleigh-Bénard convection. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2005, 72, pp.036307. ⟨hal-01023277⟩
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
Clemente Rodriguez, Eric Serre, Claude Rey. A numerical model for shallow-water flows: dynamics of the eddy shedding. WSEAS Transactions on Environment and Development, 2005, 1 (2), pp.280-287. ⟨hal-01023278⟩ Plus de détails...
Clemente Rodriguez, Eric Serre, Claude Rey. A numerical model for shallow-water flows: dynamics of the eddy shedding. WSEAS Transactions on Environment and Development, 2005, 1 (2), pp.280-287. ⟨hal-01023278⟩
Journal: WSEAS Transactions on Environment and Development
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Ekman vortices and the centrifugal instability in the counter-rotating cylindrical Couette flow. Theoretical and Computational Fluid Dynamics, 2004, 18 (2-4), pp.151-168. ⟨hal-01023276⟩ Plus de détails...
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Ekman vortices and the centrifugal instability in the counter-rotating cylindrical Couette flow. Theoretical and Computational Fluid Dynamics, 2004, 18 (2-4), pp.151-168. ⟨hal-01023276⟩
Journal: Theoretical and Computational Fluid Dynamics
Eric Serre, Ewa Tuliszka-Sznitko, Patrick Bontoux. Coupled theoretical and numerical study of the flow transition between a rotating and a stationary disk. Physics of Fluids, 2004, 16 (3), pp.688-706. ⟨hal-01023275⟩ Plus de détails...
Eric Serre, Ewa Tuliszka-Sznitko, Patrick Bontoux. Coupled theoretical and numerical study of the flow transition between a rotating and a stationary disk. Physics of Fluids, 2004, 16 (3), pp.688-706. ⟨hal-01023275⟩
Eric Serre, Peter K. Stansby, Dominique R. Laurence, Brian Launder. Ecoulement autour d'un modèle d'île conique en eau peu profonde, Revue Européenne des Eléments Finis. Revue Européenne des Éléments Finis, 2003, 12 (2-3), pp.361-371. ⟨hal-01023273⟩ Plus de détails...
Eric Serre, Peter K. Stansby, Dominique R. Laurence, Brian Launder. Ecoulement autour d'un modèle d'île conique en eau peu profonde, Revue Européenne des Eléments Finis. Revue Européenne des Éléments Finis, 2003, 12 (2-3), pp.361-371. ⟨hal-01023273⟩
Said Benjeddou, Eric Serre, Claude Rey. Application de l'approximation polytropique à la simulation numérique directe d'écoulements de gaz chauds. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2003, 332, pp.271-277. ⟨hal-01023274⟩ Plus de détails...
Said Benjeddou, Eric Serre, Claude Rey. Application de l'approximation polytropique à la simulation numérique directe d'écoulements de gaz chauds. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2003, 332, pp.271-277. ⟨hal-01023274⟩
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Ewa Tuliszka-Sznitko, Eric Serre, Patrick Bontoux. On the nature of the boundary layer instability in a closed rotor-stator cavity. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2002, 329, pp.91-99. ⟨hal-01023180⟩ Plus de détails...
Ewa Tuliszka-Sznitko, Eric Serre, Patrick Bontoux. On the nature of the boundary layer instability in a closed rotor-stator cavity. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2002, 329, pp.91-99. ⟨hal-01023180⟩
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Isabelle Raspo, Sandrine Hugues, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. Spectral projection methods for the simulation of complex three-dimensional rotating flows. Computers and Fluids, 2002, 31 (4-7), pp.745-767. ⟨hal-01023173⟩ Plus de détails...
Isabelle Raspo, Sandrine Hugues, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. Spectral projection methods for the simulation of complex three-dimensional rotating flows. Computers and Fluids, 2002, 31 (4-7), pp.745-767. ⟨hal-01023173⟩
Eric Serre, Patrick Bontoux. Vortex breakdown in a three-dimensional swirling flow. Journal of Fluid Mechanics, 2002, 459, pp.347-370. ⟨hal-01023166⟩ Plus de détails...
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Spiral and wavy vortex flows in short counter-rotating Taylor-Couette cells. International Journal of Theoretical and Computational Fluid dynamics, 2002, 16, pp.5-15. ⟨hal-01023184⟩ Plus de détails...
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Spiral and wavy vortex flows in short counter-rotating Taylor-Couette cells. International Journal of Theoretical and Computational Fluid dynamics, 2002, 16, pp.5-15. ⟨hal-01023184⟩
Journal: International Journal of Theoretical and Computational Fluid dynamics
Eric Serre, Serge Gauthier. An auto-adative multidomain pseudo-spectral technique for linear stability analysis: application to viscous compressible flows. Journal of Scientific Computing, 2002, 17 (1-4), pp.91-99. ⟨hal-01023182⟩ Plus de détails...
Eric Serre, Serge Gauthier. An auto-adative multidomain pseudo-spectral technique for linear stability analysis: application to viscous compressible flows. Journal of Scientific Computing, 2002, 17 (1-4), pp.91-99. ⟨hal-01023182⟩
A Decarlis, Marc Jaeger. Effective thermal conductivity of heterogeneous two-phase material using the self-consistent finite element method. Scripta Materialia, 2001, 44 (8-9), ⟨10.1016/S1359-6462(01)00830-2⟩. ⟨hal-01282039⟩ Plus de détails...
Advanced materials often involve the mixture of a second phase material (the inclusions) in a host phase (the matrix). Indeed, materials with very specific properties can be synthesized by controlling the nature of each phase as well as the shape and spatial distribution of the inclusions. Therefore, homogenization tools yielding accurate effective transport properties are needed. We present a numerical extension of a pure analytical treatment of the problem, namely the self-consistent method.
A Decarlis, Marc Jaeger. Effective thermal conductivity of heterogeneous two-phase material using the self-consistent finite element method. Scripta Materialia, 2001, 44 (8-9), ⟨10.1016/S1359-6462(01)00830-2⟩. ⟨hal-01282039⟩
Eric Serre, Patrick Bontoux. Three-dimensional swirling flow with a precessing vortex breakdown in a rotor-stator cylinder. Physics of Fluids, 2001, 13 (11), pp.3500-3503. ⟨hal-01023121⟩ Plus de détails...
Eric Serre, Patrick Bontoux. Three-dimensional swirling flow with a precessing vortex breakdown in a rotor-stator cylinder. Physics of Fluids, 2001, 13 (11), pp.3500-3503. ⟨hal-01023121⟩
Eric Serre, Isabelle Raspo, Patrick Bontoux, Roger Peyret. Spectral solutions of the Navier-Stokes equations for rotating flow,. Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik, 2001, 81 (1), pp.533-536. ⟨hal-01023113⟩ Plus de détails...
Eric Serre, Isabelle Raspo, Patrick Bontoux, Roger Peyret. Spectral solutions of the Navier-Stokes equations for rotating flow,. Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik, 2001, 81 (1), pp.533-536. ⟨hal-01023113⟩
Journal: Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, 2001, 22 (1), pp.82-93. ⟨hal-01023080⟩ Plus de détails...
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, 2001, 22 (1), pp.82-93. ⟨hal-01023080⟩
Journal: International Journal of Heat and Fluid Flow
Eric Serre, Jean-Pierre Pulicani. A 3D pseudospectral method for rotating flows is a cylinder. Computers and Fluids, 2001, 30 (4), pp.491-519. ⟨hal-01024303⟩ Plus de détails...
Eric Serre, Jean-Pierre Pulicani. A 3D pseudospectral method for rotating flows is a cylinder. Computers and Fluids, 2001, 30 (4), pp.491-519. ⟨hal-01024303⟩
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Direct numerical simulation and identification of complex flows in Taylor-Couette counter-rotating cavities. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2001, 329, pp.727-733. ⟨hal-01023161⟩ Plus de détails...
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Direct numerical simulation and identification of complex flows in Taylor-Couette counter-rotating cavities. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2001, 329, pp.727-733. ⟨hal-01023161⟩
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Eric Serre, Patrick Bontoux. Eclatement tourbillonnaire dans une cavité rotor-stator cylindrique. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2001, 329, pp.727-733. ⟨hal-01023151⟩ Plus de détails...
Eric Serre, Patrick Bontoux. Eclatement tourbillonnaire dans une cavité rotor-stator cylindrique. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2001, 329, pp.727-733. ⟨hal-01023151⟩
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Sofiane Meradji, Tp Lyubimova, Dv Lyubimov, B Roux. Numerical simulation of a liquid drop freely oscillating. Crystal Research and Technology, 2001, 36 (7), pp.729--744. ⟨hal-01291555⟩ Plus de détails...
Sofiane Meradji, Tp Lyubimova, Dv Lyubimov, B Roux. Numerical simulation of a liquid drop freely oscillating. Crystal Research and Technology, 2001, 36 (7), pp.729--744. ⟨hal-01291555⟩
Eric Serre, Isabelle Raspo, Patrick Bontoux. High order accurate spectral approximation for Navier-Stokes problems. Nonlinear Analysis: Theory, Methods and Applications, 2001, 47 (6), pp.4257-4268. ⟨hal-01023116⟩ Plus de détails...
Eric Serre, Isabelle Raspo, Patrick Bontoux. High order accurate spectral approximation for Navier-Stokes problems. Nonlinear Analysis: Theory, Methods and Applications, 2001, 47 (6), pp.4257-4268. ⟨hal-01023116⟩
Journal: Nonlinear Analysis: Theory, Methods and Applications
Eric Serre, Patrick Bontoux, Richard Kotarba. Numerical Simulation of the transition in three-dimensional rotating flows with walls. Boundary layer instabilities. International Journal of Computational Fluid Dynamics, 2001, 5 (2), pp.873-879. ⟨hal-01023068⟩ Plus de détails...
Eric Serre, Patrick Bontoux, Richard Kotarba. Numerical Simulation of the transition in three-dimensional rotating flows with walls. Boundary layer instabilities. International Journal of Computational Fluid Dynamics, 2001, 5 (2), pp.873-879. ⟨hal-01023068⟩
Journal: International Journal of Computational Fluid Dynamics
Eric Serre, Emilia Crespo del Arco, Patrick Bontoux. Annular and spiral patterns in flows between rotating and stationary discs. Journal of Fluid Mechanics, 2001, 434, pp.65-100. ⟨hal-01023110⟩ Plus de détails...
Different instabilities of the boundary layer flows that appear in the cavity between stationary and rotating discs are investigated using three-dimensional direct numerical simulations. The influence of curvature and confinement is studied using two geometrical configurations: (i) a cylindrical cavity including the rotation axis and (ii) an annular cavity radially confined by a shaft and a shroud. The numerical computations are based on a pseudo-spectral Chebyshev{Fourier method for solving the incompressible Navier{Stokes equations written in primitive variables. The high level accuracy of the spectral methods is imperative for the investigation of such instability structures. The basic flow is steady and of the Batchelor type. At a critical rotation rate, stationary axisymmetric and/or three-dimensional structures appear in the B¨odewadt and Ekman layers while at higher rotation rates a second transition to unsteady flow is observed. All features of the transitions are documented. A comparison of the wavenumbers, frequencies, and phase velocities of the instabilities with available theoretical and experimental results shows that both type II (or A) and type I (or B) instabilities appear, depending on flow and geometric control parameters. Interesting patterns exhibiting the coexistence of circular and spiral waves are found under certain conditions.
Eric Serre, Emilia Crespo del Arco, Patrick Bontoux. Annular and spiral patterns in flows between rotating and stationary discs. Journal of Fluid Mechanics, 2001, 434, pp.65-100. ⟨hal-01023110⟩
Eric Serre, Emilia Crespo del Arco, Patrick Bontoux. Instabilité tridimensionnelle dans une cavité inter-disque de type rotor-stator. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 1999, 326, pp.1139-1146. ⟨hal-01024305⟩ Plus de détails...
Eric Serre, Emilia Crespo del Arco, Patrick Bontoux. Instabilité tridimensionnelle dans une cavité inter-disque de type rotor-stator. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 1999, 326, pp.1139-1146. ⟨hal-01024305⟩
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
