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⟩
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⟩
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⟩
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⟩
Luc Di Gallo, Cédric Reux, Frédéric Imbeaux, Jean-François Artaud, Michal Owsiak, et al.. Coupling between a multi-physics workflow engine and an optimization framework. Computer Physics Communications, 2016, 200, pp.76-86. ⟨10.1016/j.cpc.2015.11.002⟩. ⟨hal-01461783⟩ Plus de détails...
A generic coupling method between a multi-physics workflow engine and an optimization framework is presented in this paper. The coupling architecture has been developed in order to preserve the integrity of the two frameworks. The objective is to provide the possibility to replace a framework, a workflow or an optimizer by another one without changing the whole coupling procedure or modifying the main content in each framework. The coupling is achieved by using a socket-based communication library for exchanging data between the two frameworks. Among a number of algorithms provided by optimization frameworks, Genetic Algorithms (GAs) have demonstrated their efficiency on single and multiple criteria optimization. Additionally to their robustness, GAs can handle non-valid data which may appear during the optimization. Consequently GAs work on most general cases. A parallelized framework has been developed to reduce the time spent for optimizations and evaluation of large samples. A test has shown a good scaling efficiency of this parallelized framework. This coupling method has been applied to the case of SYCOMORE (System COde for MOdeling tokamak REactor) which is a system code developed in form of a modular workflow for designing magnetic fusion reactors. The coupling of SYCOMORE with the optimization platform URANIE enables design optimization along various figures of merit and constraints. (C) 2015 EURATOM. Published by Elsevier B.V. All rights reserved.
Luc Di Gallo, Cédric Reux, Frédéric Imbeaux, Jean-François Artaud, Michal Owsiak, et al.. Coupling between a multi-physics workflow engine and an optimization framework. Computer Physics Communications, 2016, 200, pp.76-86. ⟨10.1016/j.cpc.2015.11.002⟩. ⟨hal-01461783⟩
Cédric Reux, Luc Di Gallo, Frédéric Imbeaux, Jean-François Artaud, P. Bernardi, et al.. DEMO reactor design using the new modular system code SYCOMORE. Nuclear Fusion, 2015, 55 (7), ⟨10.1088/0029-5515/55/7/073011⟩. ⟨hal-01462144⟩ Plus de détails...
A demonstration power plant (DEMO) will be the next step for fusion energy following ITER. Some of the key design questions can be addressed by simulations using system codes. System codes aim to model the whole plant with all its subsystems and identify the impact of their interactions on the design choices. The SYCOMORE code is a modular system code developed to address key questions relevant to tokamak fusion reactor design. SYCOMORE is being developed within the European Integrated Tokamak Modelling framework and provides a global view (technology and physics) of the plant. It includes modules to address plasma physics, divertor physics, breeding blankets, shield design, magnet design and the power balance of plant. The code is coupled to an optimization framework which allows one to specify figures of merit and constraints to obtain optimized designs. Examples of pulsed and steady-state DEMO designs obtained using SYCOMORE are presented. Sensitivity to design assumptions is also studied, showing that the operational domain around working points can be narrow for some cases.
Cédric Reux, Luc Di Gallo, Frédéric Imbeaux, Jean-François Artaud, P. Bernardi, et al.. DEMO reactor design using the new modular system code SYCOMORE. Nuclear Fusion, 2015, 55 (7), ⟨10.1088/0029-5515/55/7/073011⟩. ⟨hal-01462144⟩
Elena Floriani, Guido Ciraolo, Philippe Ghendrih, Yanick Sarazin, Ricardo Lima. Self-regulation of turbulence bursts and transport barriers. Plasma Physics and Controlled Fusion, 2013, 55 (9), pp.095012. ⟨10.1088/0741-3335/55/9/095012⟩. ⟨hal-00733279⟩ Plus de détails...
The interplay between turbulent bursts and transport barriers is analyzed with a simplified model of interchange turbulence in the Scrape-Off Layer of magnetically confined plasmas. The turbulent bursts spread into the transport barriers, and, depending on the competing magnitude of the burst and stopping capability of the barrier can burn through. Two models of transport barriers are presented, a hard barrier where all turbulent modes are stable in a prescribed region and a soft barrier with external plasma biasing. This process can be modeled on the basis of competing stochastic processes. For classes of probability density function of these processes one can predict the heavy tail properties of the bursts downstream from the barrier, either exponential for a leaky barrier, or with power laws, for a tight barrier. The intrinsic probing of the transport barriers by the turbulent bursts thus gives access to properties of the transport barriers. The main stochastic variables of the two models addressed here are the barrier width and the spreading distance of the turbulent bursts within the barrier together with their level of correlation. One finds that in the case of a barrier located in the Scrape-Off-Layer, the stochastic model predicts a leaky barrier with an exponential probability density function of escaping turbulent bursts in agreement with the simulation data.
Elena Floriani, Guido Ciraolo, Philippe Ghendrih, Yanick Sarazin, Ricardo Lima. Self-regulation of turbulence bursts and transport barriers. Plasma Physics and Controlled Fusion, 2013, 55 (9), pp.095012. ⟨10.1088/0741-3335/55/9/095012⟩. ⟨hal-00733279⟩
Sébastien Poncet, Stéphane Viazzo, Adrien Aubert, Riccardo da Soghe, Cosimo Bianchini. Turbulent Couette-Taylor flows with endwall effects: a numerical benchmark. International Journal of Heat and Fluid Flow, 2013, 44, pp.229-238. ⟨10.1016/j.ijheatfluidflow.2013.05.018⟩. ⟨hal-00975636⟩ Plus de détails...
The accurate prediction of fluid flow within rotating systems has a primary role for the reliability and performance of rotating machineries. The selection of a suitable model to account for the effects of turbulence on such complex flows remains an open issue in the literature. This paper reports a numerical benchmark of different approaches available within commercial CFD solvers together with results obtained by means of in-house developed or open-source available research codes exploiting a suitable Reynolds Stress Model (RSM) closure, Large Eddy Simulation (LES) and a direct numerical simulation (DNS). The predictions are compared to the experimental data of Burin et al. (2010) in an original enclosed Couette-Taylor apparatus with endcap rings. The results are discussed in details for both the mean and turbulent fields. A particular attention has been turned to the scaling of the turbulent angular momentum G with the Reynolds number Re. By DNS, G is found to be proportional to Rea, the exponent a = 1.9 being constant in our case for the whole range of Reynolds numbers. Most of the approaches predict quite well the good trends apart from the k-w SST model, which provides relatively poor agreement with the experiments even for the mean tangential velocity profile. Among the RANS models, even though no approach appears to be fully satisfactory, the RSM closure offers the best overall agreement.
Sébastien Poncet, Stéphane Viazzo, Adrien Aubert, Riccardo da Soghe, Cosimo Bianchini. Turbulent Couette-Taylor flows with endwall effects: a numerical benchmark. International Journal of Heat and Fluid Flow, 2013, 44, pp.229-238. ⟨10.1016/j.ijheatfluidflow.2013.05.018⟩. ⟨hal-00975636⟩
Journal: International Journal of Heat and Fluid Flow
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Stefano Lepri, Roberto Livi. Particle model for nonlocal heat transport in fusion plasmas. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2013, 87 (2), ⟨10.1103/PhysRevE.87.023102⟩. ⟨hal-01464720⟩ Plus de détails...
We present a simple stochastic, one-dimensional model for heat transfer in weakly collisional media as fusion plasmas. Energies of plasma particles are treated as lattice random variables interacting with a rate inversely proportional to their energy schematizing a screened Coulomb interaction. We consider both the equilibrium (microcanonical) and nonequilibrium case in which the system is in contact with heat baths at different temperatures. The model exhibits a characteristic length of thermalization that can be associated with an interaction mean free path and one observes a transition from ballistic to diffusive regime depending on the average energy of the system. A mean-field expression for heat flux is deduced from system heat transport properties. Finally, it is shown that the nonequilibrium steady state is characterized by long-range correlations. DOI: 10.1103/PhysRevE.87.023102
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Stefano Lepri, Roberto Livi. Particle model for nonlocal heat transport in fusion plasmas. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2013, 87 (2), ⟨10.1103/PhysRevE.87.023102⟩. ⟨hal-01464720⟩
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
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 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⟩
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⟩
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⟩
Nicolas Fedorczak, James Paul Gunn, Guido Ciraolo, Hugo Bufferand, Livia Isoardi, et al.. Experimental investigation on the poloidal extent of the turbulent radial flux in tokamak scrape-off layer. Journal of Nuclear Materials, 2011, 415 (1, Supplement 1), pp.S467-S470. ⟨10.1016/j.jnucmat.2010.10.034⟩. ⟨hal-01024052⟩ Plus de détails...
A consistent description of scrape-off layer transport is built from multi-diagnostic observations in ohmic discharges in Tore Supra. Fast imaging reveals the existence of relatively large filamentary structures on the low field side but not on the high field side of the torus. These filaments can exist either on open or closed magnetic flux surfaces and have a finite parallel extent from the outboard midplane. Probe electrostatic turbulence measured at the top of the plasma corresponds to the ExB convection of density burst, understood as the signature of filament propagation. Independent experiments on time-averaged parallel flows measured with a Mach probe lead to a poloidal mapping of the strongly asymmetric radial flux. This flux is centered at the outboard midplane and its poloidal half width is about 50°. The local turbulent flux on the top is consistent with the mapping.
Nicolas Fedorczak, James Paul Gunn, Guido Ciraolo, Hugo Bufferand, Livia Isoardi, et al.. Experimental investigation on the poloidal extent of the turbulent radial flux in tokamak scrape-off layer. Journal of Nuclear Materials, 2011, 415 (1, Supplement 1), pp.S467-S470. ⟨10.1016/j.jnucmat.2010.10.034⟩. ⟨hal-01024052⟩
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⟩
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⟩
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⟩
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⟩
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⟩
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⟩
