Publications de l'équipe Instabilités, Turbulence & Contrôle
2022
Rouae Ben Dhia, Nils Tilton, Denis Martinand. Impact of osmotic pressure on the stability of Taylor vortices. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2022, 933, pp.A51. ⟨10.1017/jfm.2021.1101⟩. ⟨hal-03533753⟩ Plus de détails...
We use linear stability analysis and direct numerical simulations to investigate the coupling between centrifugal instabilities, solute transport and osmotic pressure in a Taylor–Couette configuration that models rotating dynamic filtration devices. The geometry consists of a Taylor–Couette cell with a superimposed radial throughflow of solvent across two semi-permeable cylinders. Both cylinders totally reject the solute, inducing the build-up of a concentration boundary layer. The solute retroacts on the velocity field via the osmotic pressure associated with the concentration differences across the semi-permeable cylinders. Our results show that the presence of osmotic pressure strongly alters the dynamics of the centrifugal instabilities and substantially reduces the critical conditions above which Taylor vortices are observed. It is also found that this enhancement of the hydrodynamic instabilities eventually plateaus as the osmotic pressure is further increased. We propose a mechanism to explain how osmosis and instabilities cooperate and develop an analytical criterion to bound the parameter range for which osmosis fosters the hydrodynamic instabilities.
Rouae Ben Dhia, Nils Tilton, Denis Martinand. Impact of osmotic pressure on the stability of Taylor vortices. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2022, 933, pp.A51. ⟨10.1017/jfm.2021.1101⟩. ⟨hal-03533753⟩
X Litaudon, F Jenko, D Borba, D Borodin, B Braams, et al.. EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing. Plasma Physics and Controlled Fusion, IOP Publishing, 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 Braams, et al.. EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing. Plasma Physics and Controlled Fusion, IOP Publishing, 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, American Institute of Physics, 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, American Institute of Physics, 2022, 29 (1), pp.012501. ⟨10.1063/5.0064522⟩. ⟨hal-03566373⟩
M Scotto d'Abusco, G Giorgiani, J 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, IOP Publishing, 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 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, IOP Publishing, 2022, ⟨10.1088/1741-4326/ac47ad⟩. ⟨hal-03509800⟩
Gauthier Wissocq, Thomas Coratger, Gabriel Farag, Song Zhao, Pierre Boivin, et al.. Restoring the conservativity of characteristic-based segregated models: application to the hybrid lattice Boltzmann method. Physics of Fluids, American Institute of Physics, 2022, 34 (4), pp.046102. ⟨10.1063/5.0083377⟩. ⟨hal-03627520⟩ Plus de détails...
A general methodology is introduced to build conservative numerical models for fluid simulations based on segregated schemes, where mass, momentum and energy equations are solved by different methods. It is here especially designed for developing new numerical discretizations of the total energy equation, adapted to a thermal coupling with the lattice Boltzmann method (LBM). The proposed methodology is based on a linear equivalence with standard discretizations of the entropy equation, which, as a characteristic variable of the Euler system, allows efficiently decoupling the energy equation with the LBM. To this extent, any LBM scheme is equivalently written under a finite-volume formulation involving fluxes, which are further included in the total energy equation as numerical corrections. The viscous heat production is implicitly considered thanks to the knowledge of the LBM momentum flux. Three models are subsequently derived: a first-order upwind, a Lax-Wendroff and a third-order Godunov-type schemes. They are assessed on standard academic test cases: a Couette flow, entropy spot and vortex convections, a Sod shock tube, several two-dimensional Riemann problems and a shock-vortex interaction. Three key features are then exhibited: 1) the models are conservative by construction, recovering correct jump relations across shock waves, 2) the stability and accuracy of entropy modes can be explicitly controlled, 3) the low dissipation of the LBM for isentropic phenomena is preserved.
Gauthier Wissocq, Thomas Coratger, Gabriel Farag, Song Zhao, Pierre Boivin, et al.. Restoring the conservativity of characteristic-based segregated models: application to the hybrid lattice Boltzmann method. Physics of Fluids, American Institute of Physics, 2022, 34 (4), pp.046102. ⟨10.1063/5.0083377⟩. ⟨hal-03627520⟩
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, MDPI, 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, MDPI, 2022, ⟨10.3390/fluids7020063⟩. ⟨hal-03562497⟩
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, American Institute of Physics, In press. ⟨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, American Institute of Physics, In press. ⟨hal-03636905⟩
Florian Renard, Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. A linear stability analysis of compressible hybrid lattice Boltzmann methods. Journal of Computational Physics, Elsevier, 2021, 446, pp.110649. ⟨10.1016/j.jcp.2021.110649⟩. ⟨hal-03514639⟩ Plus de détails...
An original spectral study of the compressible hybrid lattice Boltzmann method (HLBM) on standard lattice is proposed. In this framework, the mass and momentum equations are addressed using the lattice Boltzmann method (LBM), while finite difference (FD) schemes solve an energy equation. Both systems are coupled with each other thanks to an ideal gas equation of state. This work aims at answering some questions regarding the numerical stability of such models, which strongly depends on the choice of numerical parameters. To this extent, several one- and two-dimensional HLBM classes based on different energy variables, formulations (primitive or conservative), collision terms and numerical schemes are scrutinized. Once appropriate corrective terms introduced, it is shown that all continuous HLBM classes recover the Navier-Stokes-Fourier behavior in the linear approximation. However, striking differences arise between HLBM classes when their discrete counterparts are analyzed. Multiple instability mechanisms arising at relatively high Mach number are pointed out and two exhaustive stabilization strategies are introduced: (1) decreasing the time step by changing the reference temperature T-r and (2) introducing a controllable numerical dissipation a via the collision operator. A complete parametric study reveals that only HLBM classes based on the primitive and conservative entropy equations are found usable for compressible applications. Finally, an innovative study of the macroscopic modal composition of the entropy classes is conducted. Through this study, two original phenomena, referred to as shear-to-entropy and entropy-to-shear transfers, are highlighted and confirmed on standard two-dimensional test cases. (C) 2021 Elsevier Inc. All rights reserved.
Florian Renard, Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. A linear stability analysis of compressible hybrid lattice Boltzmann methods. Journal of Computational Physics, Elsevier, 2021, 446, pp.110649. ⟨10.1016/j.jcp.2021.110649⟩. ⟨hal-03514639⟩
Thomas Astoul, Gauthier Wissocq, Jean-François Boussuge, Alois Sengissen, Pierre Sagaut. Lattice Boltzmann method for computational aeroacoustics on non-uniform meshes: A direct grid coupling approach. Journal of Computational Physics, Elsevier, 2021, 447, pp.110667. ⟨10.1016/j.jcp.2021.110667⟩. ⟨hal-03514616⟩ Plus de détails...
The present study proposes an accurate lattice Boltzmann direct coupling algorithm, well suited for industrial purposes, making it highly valuable for aeroacoustic applications. It is indeed known that the convection of vortical structures across a grid refinement interface, where cell size is abruptly doubled, is likely to generate spurious noise that may corrupt the solution over the whole computational domain. This issue becomes critical in the case of aeroacoustic simulations, where accurate pressure estimations are of paramount importance. Consequently, any interfering noise that may pollute the acoustic predictions must be reduced. The proposed grid refinement algorithm differs from conventionally used ones, in which an overlapping mesh layer is considered. Instead, it provides a direct connection allowing a tighter link between fine and coarse grids, especially with the use of a coherent equilibrium function shared by both grids. Moreover, the direct coupling makes the algorithm more local and prevents the duplication of points, which might be detrimental for massive parallelization. This work follows our first study (Astoul et al. 2020 [1]) on the deleterious effect of non-hydrodynamic modes crossing mesh transitions, which can be addressed using an appropriate collision model: the hybrid recursive regularization. The grid coupling algorithm is assessed in the context of computational aeroacoustics and compared to a widely-used cell-vertex algorithm. The validation benchmark includes the simulation of (1) an acoustic pulse, (2) a vortex transport by a mean flow, and finally, (3) a turbulent circular cylinder wake flow at high Reynolds number. In the end, the proposed approach is proven to drastically reduced the spurious noise generated at grid interfaces, hence, paving the way for accurate and efficient aeroacoustic simulations based on lattice Boltzmann methods. (C) 2021 Elsevier Inc. All rights reserved.
Thomas Astoul, Gauthier Wissocq, Jean-François Boussuge, Alois Sengissen, Pierre Sagaut. Lattice Boltzmann method for computational aeroacoustics on non-uniform meshes: A direct grid coupling approach. Journal of Computational Physics, Elsevier, 2021, 447, pp.110667. ⟨10.1016/j.jcp.2021.110667⟩. ⟨hal-03514616⟩
T. Coratger, G. Farag, S. Zhao, Pierre Boivin, P. Sagaut. Large-eddy lattice-Boltzmann modeling of transonic flows. Physics of Fluids, American Institute of Physics, 2021, 33 (11), pp.115112. ⟨10.1063/5.0064944⟩. ⟨hal-03424286⟩ Plus de détails...
T. Coratger, G. Farag, S. Zhao, Pierre Boivin, P. Sagaut. Large-eddy lattice-Boltzmann modeling of transonic flows. Physics of Fluids, American Institute of Physics, 2021, 33 (11), pp.115112. ⟨10.1063/5.0064944⟩. ⟨hal-03424286⟩
Felix Marlow, Jérôme Jacob, Pierre Sagaut. A multidisciplinary model coupling Lattice-Boltzmann-based CFD and a Social Force Model for the simulation of pollutant dispersion in evacuation situations. Building and Environment, Elsevier, 2021, 205, pp.108212. ⟨10.1016/j.buildenv.2021.108212⟩. ⟨hal-03597658⟩ Plus de détails...
In closed rooms with limited convection human motion can considerably affect the airflow and thus the dispersion of pollutant. However, in Computational Fluid Dynamics (CFD) simulations on air quality and safety for human beings this effect is generally not considered, which is mainly due to a lack of a well-founded and detailed estimation of the human behavior and the high computational cost of taking into account moving objects in CFD meshes. This work addresses this issue by coupling multidisciplinary methods to allow for a more realistic simulation of pollutant dispersion by taking into account the influence of human movements. A Social Force Model predicts trajectory and speed of each person moving in a complex environment. A lattice Boltzmann-based CFD tool provides a Large Eddy Simulation of the unsteady turbulent airflow with pollutant dispersion and thermal effects. And an Actuator Line Model supplies the CFD tool with body forces that mimic the impact of moving objects on the airflow, thus, avoiding computationally expensive dynamic meshing. The capability of the coupled model is demonstrated on three realistic evacuation scenarios with various pollutant sources and a wide range of scales (dimension from 10 to 100 m, occupation from 10 to 6000 persons). The results allow to access instantaneous environmental parameters like pollutant concentration for each person during the course of the evacuation, enabling the assessment of associated health risks.
Felix Marlow, Jérôme Jacob, Pierre Sagaut. A multidisciplinary model coupling Lattice-Boltzmann-based CFD and a Social Force Model for the simulation of pollutant dispersion in evacuation situations. Building and Environment, Elsevier, 2021, 205, pp.108212. ⟨10.1016/j.buildenv.2021.108212⟩. ⟨hal-03597658⟩
Felix Marlow, Jérôme Jacob, Pierre Sagaut. A multidisciplinary model coupling Lattice-Boltzmann-based CFD and a Social Force Model for the simulation of pollutant dispersion in evacuation situations. Building and Environment, Elsevier, 2021, 205, pp.108212. ⟨10.1016/j.buildenv.2021.108212⟩. ⟨hal-03514660⟩ Plus de détails...
In closed rooms with limited convection human motion can considerably affect the airflow and thus the dispersion of pollutant. However, in Computational Fluid Dynamics (CFD) simulations on air quality and safety for human beings this effect is generally not considered, which is mainly due to a lack of a well-founded and detailed estimation of the human behavior and the high computational cost of taking into account moving objects in CFD meshes. This work addresses this issue by coupling multidisciplinary methods to allow for a more realistic simulation of pollutant dispersion by taking into account the influence of human movements. A Social Force Model predicts trajectory and speed of each person moving in a complex environment. A lattice Boltzmann-based CFD tool provides a Large Eddy Simulation of the unsteady turbulent airflow with pollutant dispersion and thermal effects. And an Actuator Line Model supplies the CFD tool with body forces that mimic the impact of moving objects on the airflow, thus, avoiding computationally expensive dynamic meshing. The capability of the coupled model is demonstrated on three realistic evacuation scenarios with various pollutant sources and a wide range of scales (dimension from 10 to 100 m, occupation from 10 to 6000 persons). The results allow to access instantaneous environmental parameters like pollutant concentration for each person during the course of the evacuation, enabling the assessment of associated health risks.
Felix Marlow, Jérôme Jacob, Pierre Sagaut. A multidisciplinary model coupling Lattice-Boltzmann-based CFD and a Social Force Model for the simulation of pollutant dispersion in evacuation situations. Building and Environment, Elsevier, 2021, 205, pp.108212. ⟨10.1016/j.buildenv.2021.108212⟩. ⟨hal-03514660⟩
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, American Institute of Physics, 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, American Institute of Physics, 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, IOP Publishing, 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, IOP Publishing, 2021, 61 (11), pp.116052. ⟨10.1088/1741-4326/ac2873⟩. ⟨hal-03377162⟩
Pierre Magnico. Molecular dynamics study on water and hydroxide transfer mechanisms in PSU-g-alkyl-TMA membranes at low hydration: Effect of side chain length. International Journal of Hydrogen Energy, Elsevier, 2021, 46 (68), pp.33915-33933. ⟨10.1016/j.ijhydene.2021.07.081⟩. ⟨hal-03358207⟩ Plus de détails...
Molecular dynamics simulations with anion exchange membranes (alkyl trimethyl ammonium grafted onto polysulfone) are performed to investigate the influence of the spacer length on the transport properties, on the molecular exchange mechanisms between the functional group and the aqueous phase and on the hydrogen bond network. This is especially insightful that in this work the hydration number is small. In this condition the aqueous phase must be thought as an assembly of small clusters. The results show an unexpected dependence of the water and hydroxide (OH) diffusivity on the temperature and the water uptake. The distribution of the cluster size bonded to OH explain partially the OH diffusivity. “Hopping” and “caging” motions are observed with the self-part of the Van Hove functions even at high temperature. The characteristic time of the survival probability correlation function around the functional groups is a decreasing function of the alkyl length.
Pierre Magnico. Molecular dynamics study on water and hydroxide transfer mechanisms in PSU-g-alkyl-TMA membranes at low hydration: Effect of side chain length. International Journal of Hydrogen Energy, Elsevier, 2021, 46 (68), pp.33915-33933. ⟨10.1016/j.ijhydene.2021.07.081⟩. ⟨hal-03358207⟩
Georis Billo, Michel Belliard, Pierre Sagaut. A Finite Element Penalized Direct Forcing Immersed Boundary Method for infinitely thin obstacles in a dilatable flow. Computers & Mathematics with Applications, Elsevier, 2021, 99, pp.292-304. ⟨10.1016/j.camwa.2021.08.005⟩. ⟨hal-03514671⟩ Plus de détails...
In the framework of the development of new passive safety systems for the second and third generations of nuclear reactors, the numerical simulations, involving complex turbulent two-phase flows around thin or massive inflow obstacles, are privileged tools to model, optimize and assess new design shapes. In order to match industrial demands, computational fluid dynamics tools must be the fastest, most accurate and most robust possible. To face this issue, we have chosen to solve the Navier-Stokes equations using a projection scheme for a mixture fluid coupled with an Immersed Boundary (IB) approach: the penalized direct forcing method - a technique whose characteristics inherit from both penalty and immersed boundary methods - adapted to infinitely thin obstacles and to a Finite Element (FE) formulation. Various IB conditions (slip, no-slip or Neumann) for the velocity on the IB can be managed by imposing Dirichlet values in the vicinity of the thin obstacles. To deal with these imposed Dirichlet velocities, we investigated two variants: one in which we use the obstacle velocity and another one in which we use linear interpolations based on discrete geometrical properties of the IB (barycenters and normal vectors) and the FE basis functions. This last variant is motivated by an increase of the accuracy/computation time ratio for coarse meshes. As a first step, concerning academic test cases for one-phase dilatable-fluid laminar flows, the results obtained via those two variants are in good agreement with analytical and experimental data. Moreover, when compared to each other, the linear interpolation variant increases the spatial order of convergence as expected. An industrial test case illustrates the advantages and drawbacks of this approach. In a shortcoming second step, to face two-phase turbulent fluid simulations, some methodology modifications will be considered such as adapting the projection scheme to low-compressible fluid and immersed wall-law boundary conditions.
Georis Billo, Michel Belliard, Pierre Sagaut. A Finite Element Penalized Direct Forcing Immersed Boundary Method for infinitely thin obstacles in a dilatable flow. Computers & Mathematics with Applications, Elsevier, 2021, 99, pp.292-304. ⟨10.1016/j.camwa.2021.08.005⟩. ⟨hal-03514671⟩
Journal: Computers & Mathematics with Applications
Georis Billo, Michel Belliard, Pierre Sagaut. A Finite Element Penalized Direct Forcing Immersed Boundary Method for infinitely thin obstacles in a dilatable flow. Computers & Mathematics with Applications, Elsevier, 2021, 99, pp.292-304. ⟨10.1016/j.camwa.2021.08.005⟩. ⟨hal-03596009⟩ Plus de détails...
In the framework of the development of new passive safety systems for the second and third generations of nuclear reactors, the numerical simulations, involving complex turbulent two-phase flows around thin or massive inflow obstacles, are privileged tools to model, optimize and assess new design shapes. In order to match industrial demands, computational fluid dynamics tools must be the fastest, most accurate and most robust possible. To face this issue, we have chosen to solve the Navier-Stokes equations using a projection scheme for a mixture fluid coupled with an Immersed Boundary (IB) approach: the penalized direct forcing method-a technique whose characteristics inherit from both penalty and immersed boundary methods-adapted to infinitely thin obstacles and to a Finite Element (FE) formulation. Various IB conditions (slip, no-slip or Neumann) for the velocity on the IB can be managed by imposing Dirichlet values in the vicinity of the thin obstacles. To deal with these imposed Dirichlet velocities, we investigated two variants: one in which we use the obstacle velocity and another one in which we use linear interpolations based on discrete geometrical properties of the IB (barycenters and normal vectors) and the FE basis functions. This last variant is motivated by an increase of the accuracy/computation time ratio for coarse meshes. As a first step, concerning academic test cases for one-phase dilatable-fluid laminar flows, the results obtained via those two variants are in good agreement with analytical and experimental data. Moreover, when compared to each other, the linear interpolation variant increases the spatial order of convergence as expected. An industrial test case illustrates the advantages and drawbacks of this approach. In a shortcoming second step, to face two-phase turbulent fluid simulations, some methodology modifications will be considered such as adapting the projection scheme to low-compressible fluid and immersed wall-law boundary conditions.
Georis Billo, Michel Belliard, Pierre Sagaut. A Finite Element Penalized Direct Forcing Immersed Boundary Method for infinitely thin obstacles in a dilatable flow. Computers & Mathematics with Applications, Elsevier, 2021, 99, pp.292-304. ⟨10.1016/j.camwa.2021.08.005⟩. ⟨hal-03596009⟩
Journal: Computers & Mathematics with Applications
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, IOP Publishing, 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, IOP Publishing, 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, IOP Publishing, 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, IOP Publishing, 2021, 61 (10), pp.106019. ⟨10.1088/1741-4326/ac2026⟩. ⟨hal-03380329⟩
Johan Degrigny, Shang-Gui Cai, Jean-François Boussuge, Pierre Sagaut. Improved wall model treatment for aerodynamic flows in LBM. Computers and Fluids, Elsevier, 2021, 227, pp.105041. ⟨10.1016/j.compfluid.2021.105041⟩. ⟨hal-03326170⟩ Plus de détails...
The article deals with an improved treatment of wall models for the simulation of turbulent flows in the framework of Immersed Wall Boundaries on Cartesian grids. The emphasis is put on the implementa-tion in a Lattice-Boltzmann Method solver without loss of generality, since the proposed approach can be used in Navier-Stokes-based solvers in a straightforward way. The proposed improved wall model im-plementation relies on the combination of several key elements, namely i) the removal of grid points too close to the solid surface and ii) an original computation of wall normal velocity gradient and iii) the interpolation scheme. The new method is successfully assessed considering URANS simulations focusing on steady solutions of the Zero Pressure Gradient turbulent flat plate boundary layer and the turbulent flow around a NACA0012 airfoil at several angles of attack.
Johan Degrigny, Shang-Gui Cai, Jean-François Boussuge, Pierre Sagaut. Improved wall model treatment for aerodynamic flows in LBM. Computers and Fluids, Elsevier, 2021, 227, pp.105041. ⟨10.1016/j.compfluid.2021.105041⟩. ⟨hal-03326170⟩
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, American Institute of Physics, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03597108⟩ Plus de détails...
An immersed boundary method is coupled to a turbulent wall model and Large Eddy Simulation, within the Lattice-Boltzmann framework. The method is able to handle arbitrarily moving objects immersed in a high Reynolds number flow and to accurately capture the shear layer and near wall effects. We perform a thorough numerical study which validates the numerical method on a set of test-cases of increasing complexity, in order to demonstrate the application of this method to industrial conditions. The robustness and accuracy of the method are assessed first in a static laminar configuration, then in a mobile laminar case, and finally in a static and oscillating turbulent simulation. In all cases, the proposed method shows good results compared to the available data in the literature.
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, American Institute of Physics, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03597108⟩
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, American Institute of Physics, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03514710⟩ Plus de détails...
An immersed boundary method is coupled to a turbulent wall model and Large Eddy Simulation, within the Lattice-Boltzmann framework. The method is able to handle arbitrarily moving objects immersed in a high Reynolds number flow and to accurately capture the shear layer and near wall effects. We perform a thorough numerical study which validates the numerical method on a set of test-cases of increasing complexity, in order to demonstrate the application of this method to industrial conditions. The robustness and accuracy of the method are assessed first in a static laminar configuration, then in a mobile laminar case, and finally in a static and oscillating turbulent simulation. In all cases, the proposed method shows good results compared to the available data in the literature.
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, American Institute of Physics, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03514710⟩
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, IOP Publishing, 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, IOP Publishing, 2021, 63 (6), pp.064005. ⟨10.1088/1361-6587/abf670⟩. ⟨hal-03384547⟩
Elisa Buffa, Jérôme Jacob, Pierre Sagaut. Lattice-Boltzmann-based large-eddy simulation of high-rise building aerodynamics with inlet turbulence reconstruction. Journal of Wind Engineering and Industrial Aerodynamics, Elsevier, 2021, 212, pp.104560. ⟨10.1016/j.jweia.2021.104560⟩. ⟨hal-03596056⟩ Plus de détails...
Boltzmann-based Large-Eddy Simulation approach for wind load prediction on high-rise building is proposed and validated. An extension of the original incompressible Synthetic Eddy Method to reconstruct inlet turbulence is proposed within the Lattice-Boltzmann framework, including a low-noise frozen density variant. Extensive successful comparisons with experimental data are carried out, for both quantities defined on the building surface and in its wake. A detailed sensitivity analysis of the results with respect to inlet turbulence reconstruction, boundary conditions at the building surface and grid resolution is also provided. An almost unique set of comparisons with experimental data is presented, including mean and rms values, spectra, but also peak values of pressure at the building surface.
Elisa Buffa, Jérôme Jacob, Pierre Sagaut. Lattice-Boltzmann-based large-eddy simulation of high-rise building aerodynamics with inlet turbulence reconstruction. Journal of Wind Engineering and Industrial Aerodynamics, Elsevier, 2021, 212, pp.104560. ⟨10.1016/j.jweia.2021.104560⟩. ⟨hal-03596056⟩
Journal: Journal of Wind Engineering and Industrial Aerodynamics
M. Bahlali, H. Yoo, Julien Favier, Pierre Sagaut. A lattice Boltzmann direct coupling overset approach for the moving boundary problem. Physics of Fluids, American Institute of Physics, 2021, 33 (5), pp.053607. ⟨10.1063/5.0044994⟩. ⟨hal-03326151⟩ Plus de détails...
We propose a new direct coupling scheme based on the overset technique to tackle moving boundary problems within the lattice Boltzmann framework. The scheme is based on the interpolation of distribution functions rather than moments, that is, macroscopic variables, and includes an additional hypothesis ensuring mass and momentum conservation at the interface nodes between fixed and moving grids. The method is assessed considering four test cases and considering both the vortical and the acoustic fields. It is shown that the direct coupling method results are in very good agreement with reference results on a configuration without any moving subdomain. Moreover, it is demonstrated that the direct coupling method provides an improvement of the accuracy of the lattice Boltzmann overset algorithm for aeroacoustics. In particular, a convected vortex test case is studied and reveals that the direct coupling approach leads to a better ability to conserve the vortex structure over time, as well as a reduction in spurious acoustic distorsions at the fixed/moving interface.
M. Bahlali, H. Yoo, Julien Favier, Pierre Sagaut. A lattice Boltzmann direct coupling overset approach for the moving boundary problem. Physics of Fluids, American Institute of Physics, 2021, 33 (5), pp.053607. ⟨10.1063/5.0044994⟩. ⟨hal-03326151⟩
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, American Institute of Physics, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03597721⟩ Plus de détails...
Simulating rotating geometries in fluid flows for industrial applications remains a challenging task for general fluid solvers and in particular for the lattice Boltzmann method (LBM) due to inherent stability and accuracy problems. This work proposes an original method based on the widely used overset grids (or Chimera grids) while being integrated with a recent and optimized LBM collision operator, the hybrid recursive regularized model (HRR). The overset grids are used to actualize the rotating geometries where both the rotating and fixed meshes exist simultaneously. In the rotating mesh, the fictitious forces generated from its non-inertial rotating reference frame are taken into account by using a second order discrete forcing term. The fixed and rotating grids communicate with each other through the interpolation of the macroscopic variables. Meanwhile, the HRR collision model is selected to enhance the stability and accuracy properties of the LBM simulations by filtering out redundant higher order non-equilibrium tensors. The robustness of the overset HRR algorithm is assessed on different configurations, undergoing mid-to-high Reynolds number flows, and the method successfully demonstrates its robustness while exhibiting the second order accuracy.
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, American Institute of Physics, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03597721⟩
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, American Institute of Physics, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03326134⟩ Plus de détails...
Simulating rotating geometries in fluid flows for industrial applications remains a challenging task for general fluid solvers and in particular for the lattice Boltzmann method (LBM) due to inherent stability and accuracy problems. This work proposes an original method based on the widely used overset grids (or Chimera grids) while being integrated with a recent and optimized LBM collision operator, the hybrid recursive regularized model (HRR). The overset grids are used to actualize the rotating geometries where both the rotating and fixed meshes exist simultaneously. In the rotating mesh, the fictitious forces generated from its non-inertial rotating reference frame are taken into account by using a second order discrete forcing term. The fixed and rotating grids communicate with each other through the interpolation of the macroscopic variables. Meanwhile, the HRR collision model is selected to enhance the stability and accuracy properties of the LBM simulations by filtering out redundant higher order non-equilibrium tensors. The robustness of the overset HRR algorithm is assessed on different configurations, undergoing mid-to-high Reynolds number flows, and the method successfully demonstrates its robustness while exhibiting the second order accuracy.
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, American Institute of Physics, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03326134⟩
Shang-Gui Cai, Pierre Sagaut. Explicit wall models for large eddy simulation. Physics of Fluids, American Institute of Physics, 2021, 33 (4), pp.041703. ⟨10.1063/5.0048563⟩. ⟨hal-03597083⟩ Plus de détails...
Algebraic explicit wall models covering the entire inner region of the turbulent boundary layer are proposed to reduce the computational effort for large eddy simulation of wall-bounded turbulent flows. The proposed formulas are given in closed forms with either logarithmicor power-function-based laws of the wall, allowing straightforward evaluation of the friction velocity on near wall grids independent of their locations in the turbulent boundary layer. The performance of the proposed models is demonstrated by the wall modeled large eddy simulation of a turbulent plane channel flow.
Shang-Gui Cai, Pierre Sagaut. Explicit wall models for large eddy simulation. Physics of Fluids, American Institute of Physics, 2021, 33 (4), pp.041703. ⟨10.1063/5.0048563⟩. ⟨hal-03597083⟩
Jérémie Janin, Fabien Duval, Christophe Friess, Pierre Sagaut. A new linear forcing method for isotropic turbulence with controlled integral length scale. Physics of Fluids, American Institute of Physics, 2021, 33 (4), pp.045127. ⟨10.1063/5.0045818⟩. ⟨hal-03326165⟩ Plus de détails...
Turbulence is a common feature to all flows that surround us. Despite its ubiquity, particularly in industrial flows, it is very difficult to provide a mathematical framework to the generation of turbulent eddies. Several techniques have been proposed which are able to reproduce the main features of turbulent flows, such as realistic pressure and velocity fluctuations, exhibiting proper space- and time-correlations. These techniques are usually first evaluated upon sustained homogeneous isotropic turbulence by introducing body forces to the Navier-Stokes equations. Among these techniques, Lundgren suggested a successful forcing, applied in physical space. The latter approach unfortunately lacks predicting the integral length scale of turbulence. The present study provides a forcing method based on a reconstruction approach which consists in building fluctuations with a turbulent synthetic velocity field based on a prescribed energy spectrum model. The proposed approach is assessed by performing large-eddy simulations of a sustained homogeneous isotropic turbulence in a triply periodic box of size L = 2pi. Properties of the new forcing technique are discussed, drawing on both spatial and time correlations and also on the shape of energy spectrum together with the level of resolved turbulent kinetic energy. A special attention is put on the control of resolved turbulent energy. In this framework, an efficient selective forcing technique is derived, making use of spectral space features. The results show that the proposed approach allows to drive efficiently the resolved kinetic energy towards its target value while preserving the integral length scale independent of the domain size. It is observed that the resulting longitudinal length scale is overestimated by 13%, while the two-time correlations are recovered when using stochastic frequencies.
Jérémie Janin, Fabien Duval, Christophe Friess, Pierre Sagaut. A new linear forcing method for isotropic turbulence with controlled integral length scale. Physics of Fluids, American Institute of Physics, 2021, 33 (4), pp.045127. ⟨10.1063/5.0045818⟩. ⟨hal-03326165⟩
Florian Renard, Yongliang Feng, Jean-François Boussuge, Pierre Sagaut. Improved compressible hybrid lattice Boltzmann method on standard lattice for subsonic and supersonic flows. Computers and Fluids, Elsevier, 2021, 219, pp.104867. ⟨10.1016/j.compfluid.2021.104867⟩. ⟨hal-03326159⟩ Plus de détails...
A D2Q9 Hybrid Lattice Boltzmann Method (HLBM) is proposed for the simulation of both compressible subsonic and supersonic flows. This HLBM is an extension of the model of Feng et al. [1], which has been found, via different test cases, to be unstable for supersonic regimes. To circumvent this limitation, we propose:: (1) a new discretization of the lattice closure correction term that makes possible the simulation of supersonic flows, (2) a corrected viscous stress tensor that takes into account polyatomic gases, and (3) a novel discretization of the viscous heat production term fitting with the regularized formalism. The result is a hybrid method that resolves the mass and momentum equations with an LBM algorithm, and resolves the entropy-based energy equation with a finite volume method. This approach fully recovers the physics of the Navier-Stokes-Fourier equations with the ideal gas equation of state, and is valid from subsonic to supersonic regimes. It is then successfully assessed with both smooth flows and flows involving shocks. The proposed model is shown to be an efficient, accurate, and robust alternative to classic Navier-Stokes methods for the simulation of compressible flows.
Florian Renard, Yongliang Feng, Jean-François Boussuge, Pierre Sagaut. Improved compressible hybrid lattice Boltzmann method on standard lattice for subsonic and supersonic flows. Computers and Fluids, Elsevier, 2021, 219, pp.104867. ⟨10.1016/j.compfluid.2021.104867⟩. ⟨hal-03326159⟩
Jérémie Janin, Fabien Duval, Christophe Friess, Pierre Sagaut. A new linear forcing method for isotropic turbulence with controlled integral length scale. Physics of Fluids, American Institute of Physics, 2021, 33 (4), pp.045127. ⟨10.1063/5.0045818⟩. ⟨hal-03326165⟩ Plus de détails...
Turbulence is a common feature to all flows that surround us. Despite its ubiquity, particularly in industrial flows, it is very difficult to provide a mathematical framework for the generation of turbulent eddies. Several methods have been proposed which are able to reproduce realistic features for velocity fluctuations, exhibiting proper space- and time-correlations. Focusing on physical space forcing, these methods are usually first evaluated upon sustained homogeneous isotropic turbulence by introducing a body force to the Navier-Stokes equations. Since the pioneering work of Lundgren, these techniques usually experience difficulties in predicting the integral length scale. The present study provides a forcing through a reconstruction approach which consists in building velocity fluctuations with a prescribed energy spectrum model. The proposed approach is assessed by performing large-eddy simulations of a sustained homogeneous isotropic turbulence in a triply periodic box. Properties of this forcing technique are discussed, drawing on both spatial and time correlations and also on the shape of energy spectrum together with the level of resolved turbulent kinetic energy. A special attention is put on the control of resolved turbulent energy. In this framework, an efficient selective forcing technique is derived, making use of spectral space features. The results show that the proposed approach allows to drive efficiently the resolved kinetic energy toward its target value while preserving the integral length scale independent of the domain size. It is observed that the resulting longitudinal length scale is overestimated by 13%, while the two-time correlations are recovered when using stochastic frequencies.
Jérémie Janin, Fabien Duval, Christophe Friess, Pierre Sagaut. A new linear forcing method for isotropic turbulence with controlled integral length scale. Physics of Fluids, American Institute of Physics, 2021, 33 (4), pp.045127. ⟨10.1063/5.0045818⟩. ⟨hal-03326165⟩
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, Elsevier, 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, Elsevier, 2021, pp.101012. ⟨10.1016/j.nme.2021.101012⟩. ⟨hal-03214958⟩
S. Guo, Y. Feng, Pierre Sagaut. On the use of conservative formulation of energy equation in hybrid compressible lattice Boltzmann method. Computers and Fluids, Elsevier, 2021, 219, pp.104866. ⟨10.1016/j.compfluid.2021.104866⟩. ⟨hal-03326128⟩ Plus de détails...
Effect of density variations on mass conservation properties is widely recognized in the lattice Boltzmann method (LBM), thus non-conservative form of scalar transport equation was commonly adopted within the framework of hybrid LBM. Focusing on the compressible hybrid LBM, mass conservation and its effect on energy conservation equation are studied in this paper. Starting from the analysis on mass conservation law recovered by LBM, the consistency between conservative and non-conservative formulations of energy conservation equation based on various thermodynamic variables and lattice Boltzmann equation is addressed. Driven by the theoretical analysis, a set of modified consistent energy equations in entropy and internal energy form is derived to reduce the error terms and improve the consistency. The theoretical analysis and modified energy equations are intensively evaluated by several numerical test cases, e.g., the isentropic vortex convection, three-dimensional compressible Taylor-Green vortex and shock-vortex interaction.
S. Guo, Y. Feng, Pierre Sagaut. On the use of conservative formulation of energy equation in hybrid compressible lattice Boltzmann method. Computers and Fluids, Elsevier, 2021, 219, pp.104866. ⟨10.1016/j.compfluid.2021.104866⟩. ⟨hal-03326128⟩
S. Guo, Y. Feng, Pierre Sagaut. On the use of conservative formulation of energy equation in hybrid compressible lattice Boltzmann method. Computers and Fluids, Elsevier, 2021, 219, pp.104866. ⟨10.1016/j.compfluid.2021.104866⟩. ⟨hal-03597478⟩ Plus de détails...
Effect of density variations on mass conservation properties is widely recognized in the lattice Boltzmann method (LBM), thus non-conservative form of scalar transport equation was commonly adopted within the framework of hybrid LBM. Focusing on the compressible hybrid LBM, mass conservation and its effect on energy conservation equation are studied in this paper. Starting from the analysis on mass conservation law recovered by LBM, the consistency between conservative and non-conservative formulations of energy conservation equation based on various thermodynamic variables and lattice Boltzmann equation is addressed. Driven by the theoretical analysis, a set of modified consistent energy equations in entropy and internal energy form is derived to reduce the error terms and improve the consistency. The theoretical analysis and modified energy equations are intensively evaluated by several numerical test cases, e.g., the isentropic vortex convection, three-dimensional compressible Taylor-Green vortex and shock-vortex interaction.
S. Guo, Y. Feng, Pierre Sagaut. On the use of conservative formulation of energy equation in hybrid compressible lattice Boltzmann method. Computers and Fluids, Elsevier, 2021, 219, pp.104866. ⟨10.1016/j.compfluid.2021.104866⟩. ⟨hal-03597478⟩
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, Elsevier, 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, Elsevier, 2021, pp.101012. ⟨10.1016/j.nme.2021.101012⟩. ⟨hal-03214958⟩
Shang-Gui Cai, Johan Degrigny, Jean-François Boussuge, Pierre Sagaut. Coupling of turbulence wall models and immersed boundaries on Cartesian grids. Journal of Computational Physics, Elsevier, 2021, 429, pp.109995. ⟨10.1016/j.jcp.2020.109995⟩. ⟨hal-03597064⟩ Plus de détails...
An improved coupling of immersed boundary method and turbulence wall models on Cartesian grids is proposed, for producing smooth wall surface pressure and skin friction at high Reynolds numbers. Spurious oscillations are frequently observed on these quantities with most immersed boundary wall modeling methods, especially for the skin friction which is found to be very sensitive to the solid surface's position and orientation against the Cartesian grids. The problem originates from the irregularity of the wall distance on the stair-step grid boundaries where the immersed boundary conditions are applied. To reduce this directional error, several modifications are presented to enhance the near wall solution. First, the commonly used interpolation for the flow velocity is replaced by one for the friction velocity, which has much less variation near wall. The concept of using a fictitious point to retrieve flow fields in the wall normal direction is abandoned and the interpolation is performed in the wall parallel plane with existing fluid points. Secondly, the velocity gradients at the approximated boundary are computed with advanced schemes and the normal gradient of the tangential velocity is reconstructed from the wall laws. To further protect the near wall solution, the normal velocity gradient and the working viscosity from the Spalart-Allmaras turbulence model are enforced by their theoretical solutions in the interior fluid close to the wall. Additionally, various post-processing algorithms for reconstructing wall surface quantities and force integrations are investigated. Other related factors are also discussed for their effects on the results. The validity of present method has been demonstrated through numerical benchmark tests on a flat plate at zero pressure gradient, both aligned and inclined with respect to the grid, as well as aerodynamic cases of NACA 23012 airfoil and NASA trap wing.
Shang-Gui Cai, Johan Degrigny, Jean-François Boussuge, Pierre Sagaut. Coupling of turbulence wall models and immersed boundaries on Cartesian grids. Journal of Computational Physics, Elsevier, 2021, 429, pp.109995. ⟨10.1016/j.jcp.2020.109995⟩. ⟨hal-03597064⟩
The boundary slip error resulting from the interpolation/spreading non-reciprocity of the direct-forcing immersedboundary method is analyzed based on a simple and generic theoretical framework. In explicit implementations, the slip error scales with the Courant number, as predicted by the analysis and confirmed by lattice-Boltzmann simulation results. Using an analytical approximation of the non-reciprocity error, the immersed-boundary force can be corrected in order to prevent boundary slip and flow penetration. This a priori correction leads to a major improvement of the no-slip condition while avoiding any additional computational time or implementation effort.
Simon Gsell, Julien Favier. Direct-forcing immersed-boundary method: a simple correction preventing boundary slip error. Journal of Computational Physics, Elsevier, 2021, 435, pp.110265. ⟨10.1016/j.jcp.2021.110265⟩. ⟨hal-03425864⟩
Isabelle Cheylan, Song Zhao, Pierre Boivin, Pierre Sagaut. Compressible pressure-based Lattice-Boltzmann applied to humid air with phase change. Applied Thermal Engineering, Elsevier, 2021, pp.116868. ⟨10.1016/j.applthermaleng.2021.116868⟩. ⟨hal-03180596⟩ Plus de détails...
A new compressible pressure-based Lattice Boltzmann Method is proposed to simulate humid air flows with phase change. The variable density and compressible effects are fully resolved, effectively lifting the Boussinesq approximation commonly used, e.g. for meteorological flows. Previous studies indicate that the Boussinesq assumption can lead to errors up to 25%, but the model remains common, for compressible models often suffer from a lack of stability. In order to overcome this issue, a new pressure-based solver is proposed, exhibiting excellent stability properties. Mass and momentum conservation equations are solved by a hybrid recursive regularized Lattice-Boltzmann approach, whereas the enthalpy and species conservation equations are solved using a finite volume method. The solver is based on a pressure-based method coupled with a predictor-corrector algorithm, and incorporates a humid equation of state, as well as a specific boundary condition treatment for phase change. In particular, boundary conditions that handle mass leakage are also proposed and validated. Three test cases are investigated in order to validate this new approach: the Rayleigh-Bénard instability applied to humid air, the atmospheric rising of a condensing moist bubble, and finally the evaporation of a thin liquid film in a vertical channel. Results indicate that the proposed pressure-based Lattice-Boltzmann model is stable and accurate on all cases.
Isabelle Cheylan, Song Zhao, Pierre Boivin, Pierre Sagaut. Compressible pressure-based Lattice-Boltzmann applied to humid air with phase change. Applied Thermal Engineering, Elsevier, 2021, pp.116868. ⟨10.1016/j.applthermaleng.2021.116868⟩. ⟨hal-03180596⟩
Jincheng Lou, Jacob Johnston, Tzahi Y. Cath, Denis Martinand, Nils Tilton. Computational fluid dynamics simulations of unsteady mixing in spacer-filled direct contact membrane distillation channels. Journal of Membrane Science, Elsevier, 2021, 622, pp.118931. ⟨10.1016/j.memsci.2020.118931⟩. ⟨hal-03597607⟩ Plus de détails...
Direct contact membrane distillation (DCMD) is a promising means of concentrating brines to their saturation limit. During that process, membrane spacers play a key role in temperature polarization, concentration polarization, and mineral scaling. These interactions are not well understood, because they are difficult to study experimentally and numerically, and the flow regimes are not fully charted. We consequently develop a tailored in-house CFD code that simulates unsteady two-dimensional heat and mass transport in plate-and-frame DCMD systems with cylindrical spacers. The code uses a combination of finite-volume methods in space, projection methods in time, and recent advances in immersed boundary methods for the spacer surfaces. Using the code, we explore how the transition to unsteady laminar vortex shedding affects polarization and permeate production of DCMD systems. We show that the impact of spacers can be explained by examining the various steady and unsteady vortical flow structures generated in the bulk and near the membranes. Overall, we show that though unsteady vortex structures tend to mix temperature polarization layers with the bulk, they are not similarly able to mix the concentration layers. Rather, vortical structures tend to create regions of preferential salt accumulation. In the vortex shedding regime, the net result is that spacers often increase vapor production at the expense of increasing the risk of mineral scaling.
Jincheng Lou, Jacob Johnston, Tzahi Y. Cath, Denis Martinand, Nils Tilton. Computational fluid dynamics simulations of unsteady mixing in spacer-filled direct contact membrane distillation channels. Journal of Membrane Science, Elsevier, 2021, 622, pp.118931. ⟨10.1016/j.memsci.2020.118931⟩. ⟨hal-03597607⟩
Shang-Gui Cai, Johan Degrigny, Jean-François Boussuge, Pierre Sagaut. Coupling of turbulence wall models and immersed boundaries on Cartesian grids. Journal of Computational Physics, Elsevier, 2021, 429, pp.109995. ⟨10.1016/j.jcp.2020.109995⟩. ⟨hal-03326140⟩ Plus de détails...
An improved coupling of immersed boundary method and turbulence wall models on Cartesian grids is proposed, for producing smooth wall surface pressure and skin friction at high Reynolds numbers. Spurious oscillations are frequently observed on these quantities with most immersed boundary wall modeling methods, especially for the skin friction which is found to be very sensitive to the solid surface's position and orientation against the Cartesian grids. The problem originates from the irregularity of the wall distance on the stair-step grid boundaries where the immersed boundary conditions are applied. To reduce this directional error, several modifications are presented to enhance the near wall solution. First, the commonly used interpolation for the flow velocity is replaced by one for the friction velocity, which has much less variation near wall. The concept of using a fictitious point to retrieve flow fields in the wall normal direction is abandoned and the interpolation is performed in the wall parallel plane with existing fluid points. Secondly, the velocity gradients at the approximated boundary are computed with advanced schemes and the normal gradient of the tangential velocity is reconstructed from the wall laws. To further protect the near wall solution, the normal velocity gradient and the working viscosity from the Spalart-Allmaras turbulence model are enforced by their theoretical solutions in the interior fluid close to the wall. Additionally, various post-processing algorithms for reconstructing wall surface quantities and force integrations are investigated. Other related factors are also discussed for their effects on the results. The validity of present method has been demonstrated through numerical benchmark tests on a flat plate at zero pressure gradient, both aligned and inclined with respect to the grid, as well as aerodynamic cases of NACA 23012 airfoil and NASA trap wing.
Shang-Gui Cai, Johan Degrigny, Jean-François Boussuge, Pierre Sagaut. Coupling of turbulence wall models and immersed boundaries on Cartesian grids. Journal of Computational Physics, Elsevier, 2021, 429, pp.109995. ⟨10.1016/j.jcp.2020.109995⟩. ⟨hal-03326140⟩
Jincheng Lou, Jacob Johnston, Tzahi Cath, Denis Martinand, Nils Tilton. Computational fluid dynamics simulations of unsteady mixing in spacer-filled direct contact membrane distillation channels. Journal of Membrane Science, Elsevier, 2021, 622, pp.118931. ⟨10.1016/j.memsci.2020.118931⟩. ⟨hal-03515318⟩ Plus de détails...
Direct contact membrane distillation (DCMD) is a promising means of concentrating brines to their saturation limit. During that process, membrane spacers play a key role in temperature polarization, concentration polarization, and mineral scaling. These interactions are not well understood, because they are difficult to study experimentally and numerically, and the flow regimes are not fully charted. We consequently develop a tailored in-house CFD code that simulates unsteady two-dimensional heat and mass transport in plate-and-frame DCMD systems with cylindrical spacers. The code uses a combination of finite-volume methods in space, projection methods in time, and recent advances in immersed boundary methods for the spacer surfaces. Using the code, we explore how the transition to unsteady laminar vortex shedding affects polarization and permeate production of DCMD systems. We show that the impact of spacers can be explained by examining the various steady and unsteady vortical flow structures generated in the bulk and near the membranes. Overall, we show that though unsteady vortex structures tend to mix temperature polarization layers with the bulk, they are not similarly able to mix the concentration layers. Rather, vortical structures tend to create regions of preferential salt accumulation. In the vortex shedding regime, the net result is that spacers often increase vapor production at the expense of increasing the risk of mineral scaling.
Jincheng Lou, Jacob Johnston, Tzahi Cath, Denis Martinand, Nils Tilton. Computational fluid dynamics simulations of unsteady mixing in spacer-filled direct contact membrane distillation channels. Journal of Membrane Science, Elsevier, 2021, 622, pp.118931. ⟨10.1016/j.memsci.2020.118931⟩. ⟨hal-03515318⟩
Yongliang Feng, Johann Miranda‐fuentes, Shaolong Guo, Jérôme Jacob, Pierre Sagaut. ProLB: A Lattice Boltzmann Solver of Large‐Eddy Simulation for Atmospheric Boundary Layer Flows. Journal of Advances in Modeling Earth Systems, American Geophysical Union, 2021, 13 (3), pp.e2020MS002107. ⟨10.1029/2020MS002107⟩. ⟨hal-03326123⟩ Plus de détails...
A large-eddy simulation tool is developed for simulating the dynamics of atmospheric boundary layers (ABLs) using lattice Boltzmann method (LBM), which is an alternative approach for computational fluid dynamics and proved to be very well suited for the simulation of low-Mach flows. The equations of motion are coupled with the global complex physical models considering the coupling among several mechanisms, namely basic hydro-thermodynamics and body forces related to stratification, Coriolis force, canopy effects, humidity transport, and condensation. Mass and momentum equations are recovered by an efficient streaming, collision, and forcing process within the framework of LBM while the governing equations of temperature, liquid, and vapor water fraction are solved using a finite volume method. The implementation of wall models for ABL, subgrid models, and interaction terms related to multiphysic phenomena (e.g., stratification, condensation) is described, implemented, and assessed in this study. An immersed boundary approach is used to handle flows in complex configurations, with application to flows in realistic urban areas. Applications to both wind engineering and atmospheric pollutant dispersion are illustrated.
Yongliang Feng, Johann Miranda‐fuentes, Shaolong Guo, Jérôme Jacob, Pierre Sagaut. ProLB: A Lattice Boltzmann Solver of Large‐Eddy Simulation for Atmospheric Boundary Layer Flows. Journal of Advances in Modeling Earth Systems, American Geophysical Union, 2021, 13 (3), pp.e2020MS002107. ⟨10.1029/2020MS002107⟩. ⟨hal-03326123⟩
Journal: Journal of Advances in Modeling Earth Systems
Y. Feng, J. Miranda-Fuentes, Jérôme Jacob, Pierre Sagaut. Hybrid lattice Boltzmann model for atmospheric flows under anelastic approximation. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.036607. ⟨10.1063/5.0039516⟩. ⟨hal-03597258⟩ Plus de détails...
Lattice Boltzmann (LB) method for atmospheric dynamics is developed by considering the characteristics of the anelastic approximation. After introducing reference base state values in atmospheric flows, an LB model, with an external force term, has been constructed in anelastic framework. In the proposed anelastic LB model, mass and momentum conservation equations are solved by the LB method with a regularization procedure, and temperature field or scalar transport is simulated by finite volume method. The derived macroscopic governing equations from the anelastic model are analyzed and discussed in Chapman-Enskog asymptotic expansion. The anelastic LB model is assessed considering three benchmarks including a non-hydrostatic atmospheric inviscid convection, two-dimensional density currents, and inertia-gravity waves in stably stratified atmospheric layer. The validations demonstrate that the anelastic extension of the LB method can simulate atmospheric flows effectively and accurately. Besides, the proposed model offers a unified framework for both Boussinesq approximation and anelastic approximation, which is largely free of characteristic depth of atmospheric flows.
Y. Feng, J. Miranda-Fuentes, Jérôme Jacob, Pierre Sagaut. Hybrid lattice Boltzmann model for atmospheric flows under anelastic approximation. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.036607. ⟨10.1063/5.0039516⟩. ⟨hal-03597258⟩
Y. Feng, J. Miranda-Fuentes, Jérôme Jacob, Pierre Sagaut. Hybrid lattice Boltzmann model for atmospheric flows under anelastic approximation. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.036607. ⟨10.1063/5.0039516⟩. ⟨hal-03326143⟩ Plus de détails...
Lattice Boltzmann (LB) method for atmospheric dynamics is developed by considering the characteristics of the anelastic approximation. After introducing reference base state values in atmospheric flows, an LB model, with an external force term, has been constructed in anelastic framework. In the proposed anelastic LB model, mass and momentum conservation equations are solved by the LB method with a regularization procedure, and temperature field or scalar transport is simulated by finite volume method. The derived macroscopic governing equations from the anelastic model are analyzed and discussed in Chapman-Enskog asymptotic expansion. The anelastic LB model is assessed considering three benchmarks including a non-hydrostatic atmospheric inviscid convection, two-dimensional density currents, and inertia-gravity waves in stably stratified atmospheric layer. The validations demonstrate that the anelastic extension of the LB method can simulate atmospheric flows effectively and accurately. Besides, the proposed model offers a unified framework for both Boussinesq approximation and anelastic approximation, which is largely free of characteristic depth of atmospheric flows.
Y. Feng, J. Miranda-Fuentes, Jérôme Jacob, Pierre Sagaut. Hybrid lattice Boltzmann model for atmospheric flows under anelastic approximation. Physics of Fluids, American Institute of Physics, 2021, 33 (3), pp.036607. ⟨10.1063/5.0039516⟩. ⟨hal-03326143⟩
Simon Gsell, Umberto d'Ortona, Julien Favier. Lattice-Boltzmann simulation of creeping generalized Newtonian flows: theory and guidelines. Journal of Computational Physics, Elsevier, 2021, 429, pp.109943. ⟨10.1016/j.jcp.2020.109943⟩. ⟨hal-03166492⟩ Plus de détails...
The accuracy of the lattice-Boltzmann (LB) method is related to the relaxation time controlling the flow viscosity. In particular, it is often recommended to avoid large fluid viscosities in order to satisfy the low-Knudsen-number assumption that is essential to recover hydrodynamic behavior at the macroscopic scale, which may in principle limit the possibility of simulating creeping flows and non-Newtonian flows involving important viscosity variations. Here it is shown, based on the continuous Boltzmann equations, that a two-relaxation-time (TRT) model can however recover the steady Navier-Stokes equations without any restriction on the fluid viscosity, provided that the Knudsen number is redefined as a function of both relaxation times. This effective Knudsen number is closely related to the previously-described parameter controlling numerical errors of the TRT model, providing a consistent theory at both the discrete and continuous levels. To simulate incompressible flows, the viscous incompressibility condition M a 2 /Re 1 also needs to be satisfied, where M a and Re are the Mach and Reynolds numbers. This concept is extended by defining a local incompressibility factor, allowing one to locally control the accuracy of the simulation for flows involving varying viscosities. These theoretical arguments are illustrated based on numerical simulations of the two-dimensional flow past a square cylinder. In the case of a Newtonian flow, the viscosity independence is confirmed for relaxation times up to 10 4 , and the ratio M a 2 /Re = 0.1 is small enough to ensure reliable incompressible simulations. The Herschel-Bulkley model is employed to introduce shear-dependent viscosities in the flow. The proposed numerical strategy allows to achieve major viscosity variations, avoiding the implementation of artificial viscosity cutoff in high-viscosity regions. Highly non-linear flows are simulated over ranges of the Bingham number Bn ∈ [1, 1000] and flow index n ∈ [0.2, 1.8], and successfully compared to prior numerical works based on Navier-Stokes solvers. This work provides a general framework to simulate complex creeping flows, as encountered in many biological and industrial systems, using the lattice-Boltzmann method.
Simon Gsell, Umberto d'Ortona, Julien Favier. Lattice-Boltzmann simulation of creeping generalized Newtonian flows: theory and guidelines. Journal of Computational Physics, Elsevier, 2021, 429, pp.109943. ⟨10.1016/j.jcp.2020.109943⟩. ⟨hal-03166492⟩
Johan Degrigny, Shang-Gui Cai, Jean-François Boussuge, Pierre Sagaut. Improved wall model treatment for aerodynamic flows in LBM. Computers and Fluids, Elsevier, 2021, 227, pp.105041. ⟨10.1016/j.compfluid.2021.105041⟩. ⟨hal-03597146⟩ Plus de détails...
The article deals with an improved treatment of wall models for the simulation of turbulent flows in the framework of Immersed Wall Boundaries on Cartesian grids. The emphasis is put on the implementa-tion in a Lattice-Boltzmann Method solver without loss of generality, since the proposed approach can be used in Navier-Stokes-based solvers in a straightforward way. The proposed improved wall model im-plementation relies on the combination of several key elements, namely i) the removal of grid points too close to the solid surface and ii) an original computation of wall normal velocity gradient and iii) the interpolation scheme. The new method is successfully assessed considering URANS simulations focusing on steady solutions of the Zero Pressure Gradient turbulent flat plate boundary layer and the turbulent flow around a NACA0012 airfoil at several angles of attack.
Johan Degrigny, Shang-Gui Cai, Jean-François Boussuge, Pierre Sagaut. Improved wall model treatment for aerodynamic flows in LBM. Computers and Fluids, Elsevier, 2021, 227, pp.105041. ⟨10.1016/j.compfluid.2021.105041⟩. ⟨hal-03597146⟩
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, IOP Publishing, 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, IOP Publishing, 2021, ⟨10.1088/1741-4326/abe98b⟩. ⟨hal-03182318⟩
Jérôme Jacob, Lucie Merlier, Felix Marlow, Pierre Sagaut. Lattice Boltzmann Method-Based Simulations of Pollutant Dispersion and Urban Physics. Atmosphere, MDPI 2021, 12 (7), pp.833. ⟨10.3390/atmos12070833⟩. ⟨hal-03326148⟩ Plus de détails...
Mesocale atmospheric flows that develop in the boundary layer or microscale flows that develop in urban areas are challenging to predict, especially due to multiscale interactions, multiphysical couplings, land and urban surface thermal and geometrical properties and turbulence. However, these different flows can indirectly and directly affect the exposure of people to deteriorated air quality or thermal environment, as well as the structural and energy loads of buildings. Therefore, the ability to accurately predict the different interacting physical processes determining these flows is of primary importance. To this end, alternative approaches based on the lattice Boltzmann method (LBM) wall model large eddy simulations (WMLESs) appear particularly interesting as they provide a suitable framework to develop efficient numerical methods for the prediction of complex large or smaller scale atmospheric flows. In particular, this article summarizes recent developments and studies performed using the hybrid recursive regularized collision model for the simulation of complex or/and coupled turbulent flows. Different applications to the prediction of meteorological humid flows, urban pollutant dispersion, pedestrian wind comfort and pressure distribution on urban buildings including uncertainty quantification are especially reviewed. For these different applications, the accuracy of the developed approach was assessed by comparison with experimental and/or numerical reference data, showing a state of the art performance. Ongoing developments focus now on the validation and prediction of indoor environmental conditions including thermal mixing and pollutant dispersion in different types of rooms equipped with heat, ventilation and air conditioning systems.
Jérôme Jacob, Lucie Merlier, Felix Marlow, Pierre Sagaut. Lattice Boltzmann Method-Based Simulations of Pollutant Dispersion and Urban Physics. Atmosphere, MDPI 2021, 12 (7), pp.833. ⟨10.3390/atmos12070833⟩. ⟨hal-03326148⟩
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, IOP Publishing, 2021, ⟨10.1088/1361-6587/abf03f 2021⟩. ⟨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, IOP Publishing, 2021, ⟨10.1088/1361-6587/abf03f 2021⟩. ⟨hal-03144400⟩
G. Farag, T. Coratger, G. Wissocq, S. Zhao, Pierre Boivin, et al.. A unified hybrid lattice-Boltzmann method for compressible flows: Bridging between pressure-based and density-based methods. Physics of Fluids, American Institute of Physics, 2021, 33 (8), pp.086101. ⟨10.1063/5.0057407⟩. ⟨hal-03324229⟩ Plus de détails...
A unified expression for high-speed compressible segregated consistent lattice Boltzmann methods, namely, pressure-based and improved density-based methods, is given. It is theoretically proved that in the absence of forcing terms, these approaches are strictly identical and can be recast in a unique form. An important result is that the difference with classical density-based methods lies in the addition of fourth-order term in the equilibrium function. It is also shown that forcing terms used to balance numerical errors in both original pressure-based and improved density-based methods can be written in a generalized way. A hybrid segregated efficient lattice-Boltzmann for compressible flow based on this unified model, equipped with a recursive regularization kernel, is proposed and successfully assessed on a wide set of test cases with and without shock waves.
G. Farag, T. Coratger, G. Wissocq, S. Zhao, Pierre Boivin, et al.. A unified hybrid lattice-Boltzmann method for compressible flows: Bridging between pressure-based and density-based methods. Physics of Fluids, American Institute of Physics, 2021, 33 (8), pp.086101. ⟨10.1063/5.0057407⟩. ⟨hal-03324229⟩
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, IOP Publishing, 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, IOP Publishing, 2021, 61 (12), pp.126015. ⟨10.1088/1741-4326/ac2439⟩. ⟨hal-03420146⟩
B Dudson, W Gracias, R Jorge, A Nielsen, J Olsen, et al.. Edge turbulence in ISTTOK: a multi-code fluid validation. Plasma Physics and Controlled Fusion, IOP Publishing, 2021. ⟨hal-03179634⟩ Plus de détails...
B Dudson, W Gracias, R Jorge, A Nielsen, J Olsen, et al.. Edge turbulence in ISTTOK: a multi-code fluid validation. Plasma Physics and Controlled Fusion, IOP Publishing, 2021. ⟨hal-03179634⟩
Jérôme Jacob, Lucie Merlier, Felix Marlow, Pierre Sagaut. Lattice Boltzmann Method-Based Simulations of Pollutant Dispersion and Urban Physics. Atmosphere, MDPI 2021, 12 (7), pp.833. ⟨10.3390/atmos12070833⟩. ⟨hal-03326148⟩ Plus de détails...
Mesocale atmospheric flows that develop in the boundary layer or microscale flows that develop in urban areas are challenging to predict, especially due to multiscale interactions, multiphysical couplings, land and urban surface thermal and geometrical properties and turbulence. However, these different flows can indirectly and directly affect the exposure of people to deteriorated air quality or thermal environment, as well as the structural and energy loads of buildings. Therefore, the ability to accurately predict the different interacting physical processes determining these flows is of primary importance. To this end, alternative approaches based on the lattice Boltzmann method (LBM) wall model large eddy simulations (WMLESs) appear particularly interesting as they provide a suitable framework to develop efficient numerical methods for the prediction of complex large or smaller scale atmospheric flows. In particular, this article summarizes recent developments and studies performed using the hybrid recursive regularized collision model for the simulation of complex or/and coupled turbulent flows. Different applications to the prediction of meteorological humid flows, urban pollutant dispersion, pedestrian wind comfort and pressure distribution on urban buildings including uncertainty quantification are especially reviewed. For these different applications, the accuracy of the developed approach was assessed by comparison with experimental and/or numerical reference data, showing a state of the art performance. Ongoing developments focus now on the validation and prediction of indoor environmental conditions including thermal mixing and pollutant dispersion in different types of rooms equipped with heat, ventilation and air conditioning systems.
Jérôme Jacob, Lucie Merlier, Felix Marlow, Pierre Sagaut. Lattice Boltzmann Method-Based Simulations of Pollutant Dispersion and Urban Physics. Atmosphere, MDPI 2021, 12 (7), pp.833. ⟨10.3390/atmos12070833⟩. ⟨hal-03326148⟩
Shaolong Guo, Wen-Quan Tao. A robustness-enhanced method for Riemann solver. International Journal of Heat and Mass Transfer, Elsevier, 2020, 166, pp.120757. ⟨10.1016/j.ijheatmasstransfer.2020.120757⟩. ⟨hal-03597492⟩ Plus de détails...
The appearance of shock anomaly is a major unsolved problem for some low diffusion schemes when simulating the hypersonic flow. In this paper, a simple method is proposed to enhance the robustness of the low diffusion schemes to overcome the shock anomaly. The main idea of this method is adding an appropriate extra term to the original low diffusion schemes without influencing the accuracy in aerodynamic heating prediction. This extra term is derived from the difference between the flux splitting scheme (FVS) and the advection upstream splitting method+ (AUSM+). Adding this term to three low diffusion schemes, seven typical numerical tests are conducted to examine the capability of those schemes. Numerical results show that the three new schemes turn out to be carbuncle-free and shock-stable without losing their original accuracy in prediction of aerodynamic heating, validating the feasibility and reliability of the proposed method.
Shaolong Guo, Wen-Quan Tao. A robustness-enhanced method for Riemann solver. International Journal of Heat and Mass Transfer, Elsevier, 2020, 166, pp.120757. ⟨10.1016/j.ijheatmasstransfer.2020.120757⟩. ⟨hal-03597492⟩
Journal: International Journal of Heat and Mass Transfer
S. Zhao, G. Farag, Pierre Boivin, P. Sagaut. Toward fully conservative hybrid lattice Boltzmann methods for compressible flows. Physics of Fluids, American Institute of Physics, 2020, 32 (12), pp.126118. ⟨10.1063/5.0033245⟩. ⟨hal-03087980⟩ Plus de détails...
S. Zhao, G. Farag, Pierre Boivin, P. Sagaut. Toward fully conservative hybrid lattice Boltzmann methods for compressible flows. Physics of Fluids, American Institute of Physics, 2020, 32 (12), pp.126118. ⟨10.1063/5.0033245⟩. ⟨hal-03087980⟩
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, Elsevier, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-02944327⟩ Plus de détails...
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, Elsevier, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-02944327⟩
Journal: International Journal of Heat and Fluid Flow
Tatyana Lyubimova, Anatoly Lepikhin, Yanina Parshakova, Vadim Kolchanov, Carlo Gualtieri, et al.. A Numerical Study of the Influence of Channel-Scale Secondary Circulation on Mixing Processes Downstream of River Junctions. Water, MDPI, 2020, 12 (11), pp.2969. ⟨10.3390/w12112969⟩. ⟨hal-02989736⟩ Plus de détails...
A rapid downstream weakening of the processes that drive the intensity of transverse mixing at the confluence of large rivers has been identified in the literature and attributed to the progressive reduction in channel scale secondary circulation and shear-driven mixing with distance downstream from the junction. These processes are investigated in this paper using a three-dimensional computation of the Reynolds averaged Navier Stokes equations combined with a Reynolds stress turbulence model for the confluence of the Kama and Vishera rivers in the Russian Urals. Simulations were carried out for three different configurations: an idealized planform with a rectangular cross-section (R), the natural planform with a rectangular cross-section (P), and the natural planform with the measured bathymetry (N), each one for three different discharge ratios. Results show that in the idealized configuration (R), the initial vortices that form due to channel-scale pressure gradients decline rapidly with distance downstream. Mixing is slow and incomplete at more than 10 multiples of channel width downstream from the junction corner. However, when the natural planform and bathymetry are introduced (N), rates of mixing increase dramatically at the junction corner and are maintained with distance downstream. Comparison with the P case suggests that it is the bathymetry that drives the most rapid mixing and notably when the discharge ratio is such that a single channel-scale vortex develops aided by curvature in the post junction channel. This effect is strongest when the discharge of the tributary that has the same direction of curvature as the post junction channel is greatest. A comprehensive set of field data are required to test this conclusion. If it holds, theoretical models of mixing processes in rivers will need to take into account the effects of bathymetry upon the interaction between river discharge ratio, secondary circulation development, and mixing rates.
Tatyana Lyubimova, Anatoly Lepikhin, Yanina Parshakova, Vadim Kolchanov, Carlo Gualtieri, et al.. A Numerical Study of the Influence of Channel-Scale Secondary Circulation on Mixing Processes Downstream of River Junctions. Water, MDPI, 2020, 12 (11), pp.2969. ⟨10.3390/w12112969⟩. ⟨hal-02989736⟩
S. Guo, Yongliang Feng, Jérôme Jacob, F. Renard, Pierre Sagaut. An efficient lattice Boltzmann method for compressible aerodynamics on D3Q19 lattice. Journal of Computational Physics, Elsevier, 2020, 418, pp.109570. ⟨10.1016/j.jcp.2020.109570⟩. ⟨hal-02960161⟩ Plus de détails...
An efficient lattice Boltzmann (LB) model relying on a hybrid recursive regularization (HRR) collision operator on D3Q19 stencil is proposed for the simulation of three-dimensional high-speed compressible flows in both subsonic and supersonic regimes. An improved thermal equilibrium distribution function on D3Q19 lattice is derived to reduce the complexity of correcting terms. A simple shock capturing scheme and an upwind biased discretization of correction terms are implemented for supersonic flows with shocks. Mass and momentum equations are recovered by an efficient streaming, collision and forcing process on D3Q19 lattice. Then a non-conservative formulation of the entropy evolution equation is used, that is solved using a finite volume method. The proposed method is assessed considering the simulation of i) 2D isentropic vortex convection, ii) 3D non-isothermal acoustic pulse, iii) 2D supersonic flow over a bump, iv) 3D shock explosion in a box, v) 2D vortex interaction with shock wave, vi) 2D laminar flows over a flat plate at Ma of 0.5, 1.0 and 1.5.
S. Guo, Yongliang Feng, Jérôme Jacob, F. Renard, Pierre Sagaut. An efficient lattice Boltzmann method for compressible aerodynamics on D3Q19 lattice. Journal of Computational Physics, Elsevier, 2020, 418, pp.109570. ⟨10.1016/j.jcp.2020.109570⟩. ⟨hal-02960161⟩
Thomas Astoul, Gauthier Wissocq, Jean-François Boussuge, Alois Sengissen, Pierre Sagaut. Analysis and reduction of spurious noise generated at grid refinement interfaces with the lattice Boltzmann method. Journal of Computational Physics, Elsevier, 2020, 418, pp.109645. ⟨10.1016/j.jcp.2020.109645⟩. ⟨hal-02960150⟩ Plus de détails...
The present study focuses on the unphysical effects induced by the use of non-uniform grids in the lattice Boltzmann method. In particular, the convection of vortical structures across a grid refinement interface is likely to generate spurious noise that may impact the whole computation domain. This issue becomes critical in the case of aeroacoustic simulations, where accurate pressure estimations are of paramount importance. The purpose of this article is to identify the issues occurring at the interface and to propose possible solutions yielding significant improvements for aeroacoustic simulations. More specifically, this study highlights the critical involvement of non-physical modes in the generation of spurious vorticity and acoustics. The identification of these modes is made possible thanks to linear stability analyses performed in the fluid core, and non-hydrodynamic sensors specifically developed to systematically emphasize them during a simulation. Investigations seeking pure acoustic waves and sheared flows allow for isolating the contribution of each mode. An important result is that spurious wave generation is intrinsically due to the change in the grid resolution (i.e. aliasing) independently of the details of the grid transition algorithm. Finally, the solution proposed to minimize spurious wave amplitude consists of choosing an appropriate collision model in the fluid core so as to cancel the non-hydrodynamic mode contribution regardless the grid coupling algorithm. Results are validated on a convected vortex and on a turbulent flow around a cylinder where a huge reduction of both spurious noise and vorticity are obtained.
Thomas Astoul, Gauthier Wissocq, Jean-François Boussuge, Alois Sengissen, Pierre Sagaut. Analysis and reduction of spurious noise generated at grid refinement interfaces with the lattice Boltzmann method. Journal of Computational Physics, Elsevier, 2020, 418, pp.109645. ⟨10.1016/j.jcp.2020.109645⟩. ⟨hal-02960150⟩
M. Meldi, A. Mariotti, M. Salvetti, P. Sagaut. Numerical investigation of skewed spatially evolving mixing layers. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2020, 897, pp.A35. ⟨10.1017/jfm.2020.407⟩. ⟨hal-03251559⟩ Plus de détails...
The sensitivity of turbulent dynamics in spatially evolving mixing layers to small skew angles is investigated via direct numerical simulation. Angle is a measure of the lack of parallelism between the two asymptotic flows, whose interaction creates the turbulent mixing region. The analysis is performed considering a large range of values of the shear intensity parameter . This two-dimensional parameter space is explored using the results of a database of 18 direct numerical simulations. Instantaneous fields as well as time-averaged quantities are investigated, highlighting important mechanisms in the emergence of turbulence and its characteristics for this class of flows. In addition, a stochastic approach is used in which and are considered as random variables with a given probability distribution. The response surfaces of flow statistics in the parameter space are built through non-intrusive generalized polynomial chaos. It is found that variations of the parameter have a primary effect on the growth of the mixing region. A secondary effect associated with is observed as well. Higher values for the skew angle are responsible for a rapid increase in growth of the inlet structures, enhancing the development of the mixing region. The impact on the turbulence features and, in particular, on the Reynolds stress tensor is also significant. A modification of the normalized diagonal components of the Reynolds stress tensor due to is observed. In addition, the interaction between the parameters and is here the governing element.
M. Meldi, A. Mariotti, M. Salvetti, P. Sagaut. Numerical investigation of skewed spatially evolving mixing layers. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2020, 897, pp.A35. ⟨10.1017/jfm.2020.407⟩. ⟨hal-03251559⟩
Etienne Loiseau, Simon Gsell, Aude Nommick, Charline Jomard, Delphine Gras, et al.. Active mucus–cilia hydrodynamic coupling drives self-organization of human bronchial epithelium. Nature Physics, Nature Publishing Group, 2020, ⟨10.1038/s41567-020-0980-z⟩. ⟨hal-02914172⟩ Plus de détails...
The respiratory tract is protected by mucus, a complex fluid transported along the epithelial surface by the coordinated beating of millions of microscopic cilia, hence the name of mucociliary clearance. Its impairment is associated with all severe chronic respiratory diseases. Yet, the relationship between ciliary density and the spatial scale of mucus transport, as well as the mechanisms that drive ciliary-beat orientations are much debated. Here, we show on polarized human bronchial epithelia that mucus swirls and circular orientational order of the underlying ciliary beats emerge and grow during ciliogenesis, until a macroscopic mucus transport is achieved for physiological ciliary densities. By establishing that the macroscopic ciliary-beat order is lost and recovered by removing and adding mucus, respectively, we demonstrate that cilia–mucus hydrodynamic interactions govern the collective dynamics of ciliary-beat directions. We propose a two-dimensional model that predicts a phase diagram of mucus transport in accordance with the experiments. This paves the way to a predictive in silico modelling of bronchial mucus transport in health and disease.
Etienne Loiseau, Simon Gsell, Aude Nommick, Charline Jomard, Delphine Gras, et al.. Active mucus–cilia hydrodynamic coupling drives self-organization of human bronchial epithelium. Nature Physics, Nature Publishing Group, 2020, ⟨10.1038/s41567-020-0980-z⟩. ⟨hal-02914172⟩
Uwe Ehrenstein, Jérémie Labasse, Philippe Meliga. Numerical exploration of the pitching plate parameter space with application to thrust scaling. Applied Ocean Research, Elsevier, 2020, 101, pp.102278. ⟨10.1016/j.apor.2020.102278⟩. ⟨hal-03235146⟩ Plus de détails...
The thrust performance of a two-dimensional plate pitching harmonically in a uniform flow is assessed numerically using the OpenFOAM toolbox [1]. The mesh displacement vector associated with the rigid body motion is computed as the solution of a Laplace equation with variable diffusivity, using the appropriate mesh manipulation class of the toolbox. For a Reynolds number of 2000, the accuracy of the pressure and viscous stress distributions is assessed by comparison with reference data available for an equivalent fluid configuration. The efficiency and flexibility of the solver allows exploring large ranges of the pitching parameter space, that is the pitching frequency, amplitude and pivot-point location of the pitching plate. The forces induced by the pitching motion are computed for pitching amplitudes up to 15 ∘ , for Strouhal numbers varying between 0.2 and 0.5 and for different pitch pivot points. Performing a thrust scaling analysis, a classical theoretical model for the swimming of a waving plate is reliably fitted to the numerical pressure force data. The dependence of the time averaged thrust with the pitching axis is shown to be predicted accurately by a classical potential flow formula (known as Garrick's theory) for pivot points within the front quarter of the plate. The viscous drag is computed as well for the Reynolds number 2000. The time-averaged values are shown to depend on the pitching amplitude and frequency and for instance a Blasius-type scaling, sometimes used to model the viscous drag correction for oscillating two-dimensional foils in this Reynolds number range, is not reliable.
Uwe Ehrenstein, Jérémie Labasse, Philippe Meliga. Numerical exploration of the pitching plate parameter space with application to thrust scaling. Applied Ocean Research, Elsevier, 2020, 101, pp.102278. ⟨10.1016/j.apor.2020.102278⟩. ⟨hal-03235146⟩
Jérémie Labasse, Uwe Ehrenstein, Philippe Meliga. Numerical exploration of the pitching plate parameter space with application to thrust scaling. Applied Ocean Research, Elsevier, 2020, 101, pp.102278. ⟨10.1016/j.apor.2020.102278⟩. ⟨hal-02903603⟩ Plus de détails...
Jérémie Labasse, Uwe Ehrenstein, Philippe Meliga. Numerical exploration of the pitching plate parameter space with application to thrust scaling. Applied Ocean Research, Elsevier, 2020, 101, pp.102278. ⟨10.1016/j.apor.2020.102278⟩. ⟨hal-02903603⟩
Uwe Ehrenstein, Jérémie Labasse, Philippe Meliga. Numerical exploration of the pitching plate parameter space with application to thrust scaling. Applied Ocean Research, Elsevier, 2020, 101, pp.102278. ⟨10.1016/j.apor.2020.102278⟩. ⟨hal-03235146⟩ Plus de détails...
The thrust performance of a two-dimensional plate pitching harmonically in a uniform flow is assessed numerically using the OpenFOAM toolbox [1]. The mesh displacement vector associated with the rigid body motion is computed as the solution of a Laplace equation with variable diffusivity, using the appropriate mesh manipulation class of the toolbox. For a Reynolds number of 2000, the accuracy of the pressure and viscous stress distributions is assessed by comparison with reference data available for an equivalent fluid configuration. The efficiency and flexibility of the solver allows exploring large ranges of the pitching parameter space, that is the pitching frequency, amplitude and pivot-point location of the pitching plate. The forces induced by the pitching motion are computed for pitching amplitudes up to 15 ∘ , for Strouhal numbers varying between 0.2 and 0.5 and for different pitch pivot points. Performing a thrust scaling analysis, a classical theoretical model for the swimming of a waving plate is reliably fitted to the numerical pressure force data. The dependence of the time averaged thrust with the pitching axis is shown to be predicted accurately by a classical potential flow formula (known as Garrick's theory) for pivot points within the front quarter of the plate. The viscous drag is computed as well for the Reynolds number 2000. The time-averaged values are shown to depend on the pitching amplitude and frequency and for instance a Blasius-type scaling, sometimes used to model the viscous drag correction for oscillating two-dimensional foils in this Reynolds number range, is not reliable.
Uwe Ehrenstein, Jérémie Labasse, Philippe Meliga. Numerical exploration of the pitching plate parameter space with application to thrust scaling. Applied Ocean Research, Elsevier, 2020, 101, pp.102278. ⟨10.1016/j.apor.2020.102278⟩. ⟨hal-03235146⟩
Sylvia Wilhelm, Jérôme Jacob, Pierre Sagaut. A New Explicit Algebraic Wall Model for LES of Turbulent Flows Under Adverse Pressure Gradient. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2020, ⟨10.1007/s10494-020-00181-7⟩. ⟨hal-02960184⟩ Plus de détails...
A new explicit algebraic wall law for the Large Eddy Simulation of flows with adverse pressure gradient is proposed. This new wall law, referred as adverse pressure gradient power law (APGPL), is developed starting from the power-law of Werner and Wengle (Turbulent Shear Flows, vol 8, Springer, New York, pp 155-168, 1993) in order to mimic an implicit non-equilibrium log-law based on Afzal's law (Afzal, IUTAM Symposium on Asymptotic Methods for Turbulent Shear Flows at High Reynolds Numbers, Kluwer Academic Publishers, Bochum, pp 95-118, 1996). No iterative method is needed for the evaluation of the wall shear stress from the APGPL contrary to the majority of models available in the literature. The APGPL model relies on the definition of three modes: the equilibrium power-law is used in regions of no or favourable pressure gradient, the APGPL is used in regions of adverse pressure gradient, and no wall model is used in separated flow regions. This model is assessed via Large Eddy Simulations of flows involving adverse pressure gradient and boundary layer separation using the Lattice Boltzmann Method on uniform nested grids. The flow around a clean and iced NACA23012 airfoil at Reynolds numberRe=1.88 x 10(6) and the flow over the LAGOON landing gear at Re=1.59x10(6) are considered. Results are found in good agreement with those obtained by the non-equilibrium log-law and experimental and numerical data available in the literature.
Sylvia Wilhelm, Jérôme Jacob, Pierre Sagaut. A New Explicit Algebraic Wall Model for LES of Turbulent Flows Under Adverse Pressure Gradient. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2020, ⟨10.1007/s10494-020-00181-7⟩. ⟨hal-02960184⟩
Shahram Khazaie, Régis Cottereau. Influence of local cubic anisotropy on the transition towards an equipartition regime in a 3D texture-less random elastic medium. Wave Motion, Elsevier, 2020, 96, pp.102574. ⟨10.1016/j.wavemoti.2020.102574⟩. ⟨hal-02566857⟩ Plus de détails...
At long lapse times in randomly fluctuating media with macroscopic isotropy (texture-less media), the energy of elastic waves is equipartitioned between compressional (P) and shear (S) waves. This property is independent of the local isotropy or anisotropy of the heterogeneous constitutive tensor and of the type of source. However the local symmetry of the constitutive tensor does influence the rate of convergence to equipartition and this paper discusses the precise influence of local anisotropy on the time required to reach equipartition. More particularly, a randomly-fluctuating medium is considered, whose behavior is statistically isotropic, and locally cubic. After calculating all the differential and total scattering cross-sections in that case, an analytical formula is derived for the rate of convergence to the equipartition regime, function of the second-order statistics of the mechanical parameter fields (bulk and shear moduli and anisotropy parameter). The local anisotropy is shown to influence strongly that transition rate, with a faster transition when the fluctuations of the anisotropy parameter are positively correlated to those of the shear modulus. A numerical model is constructed to illustrate numerically these results. Since the asymptotic regime of equipartition cannot be simulated directly because it would require too large a computational domain, boundaries are introduced and mechanical properties are chosen so as to minimize their influence on equipartition.
Shahram Khazaie, Régis Cottereau. Influence of local cubic anisotropy on the transition towards an equipartition regime in a 3D texture-less random elastic medium. Wave Motion, Elsevier, 2020, 96, pp.102574. ⟨10.1016/j.wavemoti.2020.102574⟩. ⟨hal-02566857⟩
G. Farag, S. Zhao, T. Coratger, Pierre Boivin, G. Chiavassa, et al.. A pressure-based regularized lattice-Boltzmann method for the simulation of compressible flows. Physics of Fluids, American Institute of Physics, 2020, 32 (6), pp.066106. ⟨10.1063/5.0011839⟩. ⟨hal-02885427⟩ Plus de détails...
A new pressure-based Lattice-Boltzmann method (HRR-p) is proposed for the simulation of flows for Mach numbers ranging from 0 to 1.5. Compatible with nearest neighbor lattices (e.g. D3Q19), the model consists of a predictor step comparable to classical athermal Lattice-Boltzmann methods, appended with a fully local and explicit correction step for the pressure. Energy conservation-for which the Hermi-tian quadrature is not accurate enough on such lattice-is solved via a classical finite volume MUSCL-Hancock scheme based on the entropy equation. The Euler part of the model is then validated for the transport of three canonical modes (vortex, en-tropy, and acoustic propagation), while its diffusive/viscous properties are assessed via thermal Couette flow simulations. All results match the analytical solutions, with very limited dissipation. Lastly, the robustness of the method is tested in a one dimensional shock tube and a two-dimensional shock-vortex interaction.
G. Farag, S. Zhao, T. Coratger, Pierre Boivin, G. Chiavassa, et al.. A pressure-based regularized lattice-Boltzmann method for the simulation of compressible flows. Physics of Fluids, American Institute of Physics, 2020, 32 (6), pp.066106. ⟨10.1063/5.0011839⟩. ⟨hal-02885427⟩
Y. Feng, S. Guo, J. Jacob, P. Sagaut. Grid refinement in the three-dimensional hybrid recursive regularized lattice Boltzmann method for compressible aerodynamics. Physical Review E , American Physical Society (APS), 2020, 101 (6), pp.063302. ⟨10.1103/PhysRevE.101.063302⟩. ⟨hal-02892273⟩ Plus de détails...
Grid refinement techniques are of paramount importance for computational fluid dynamics approaches relying on the use of Cartesian grids. This is especially true of solvers dedicated to aerodynamics, in which the capture of thin shear layers require the use of small cells. In this paper, a three-dimensional grid refinement technique is developed within the framework of hybrid recursive regularized lattice Boltzmann method (HRR-LBM) for compressible high-speed flows, which is an efficient collide-stream-type method on a compact D3Q19 stencil. The proposed method is successfully assessed considering several test cases, namely, an isentropic vortex propagating through transition interface, shock-vortex interaction with intersection between grid refinement interface and shock corrugation, and transonic flows over three-dimensional DLR-M6 wing with seven levels of grid refinement.
Y. Feng, S. Guo, J. Jacob, P. Sagaut. Grid refinement in the three-dimensional hybrid recursive regularized lattice Boltzmann method for compressible aerodynamics. Physical Review E , American Physical Society (APS), 2020, 101 (6), pp.063302. ⟨10.1103/PhysRevE.101.063302⟩. ⟨hal-02892273⟩
Y. Feng, S. Guo, J. Jacob, P. Sagaut. Grid refinement in the three-dimensional hybrid recursive regularized lattice Boltzmann method for compressible aerodynamics. Physical Review E , American Physical Society (APS), 2020, 101 (6), pp.063302. ⟨10.1103/PhysRevE.101.063302⟩. ⟨hal-03228997⟩ Plus de détails...
Grid refinement techniques are of paramount importance for computational fluid dynamics approaches relying on the use of Cartesian grids. This is especially true of solvers dedicated to aerodynamics, in which the capture of thin shear layers require the use of small cells. In this paper, a three-dimensional grid refinement technique is developed within the framework of hybrid recursive regularized lattice Boltzmann method (HRR-LBM) for compressible high-speed flows, which is an efficient collide-stream-type method on a compact D3Q19 stencil. The proposed method is successfully assessed considering several test cases, namely, an isentropic vortex propagating through transition interface, shock-vortex interaction with intersection between grid refinement interface and shock corrugation, and transonic flows over three-dimensional DLR-M6 wing with seven levels of grid refinement.
Y. Feng, S. Guo, J. Jacob, P. Sagaut. Grid refinement in the three-dimensional hybrid recursive regularized lattice Boltzmann method for compressible aerodynamics. Physical Review E , American Physical Society (APS), 2020, 101 (6), pp.063302. ⟨10.1103/PhysRevE.101.063302⟩. ⟨hal-03228997⟩
Y. Feng, S. Guo, J. Jacob, P. Sagaut. Grid refinement in the three-dimensional hybrid recursive regularized lattice Boltzmann method for compressible aerodynamics. Physical Review E , American Physical Society (APS), 2020, 101 (6), pp.063302. ⟨10.1103/PhysRevE.101.063302⟩. ⟨hal-03228997⟩ Plus de détails...
Grid refinement techniques are of paramount importance for computational fluid dynamics approaches relying on the use of Cartesian grids. This is especially true of solvers dedicated to aerodynamics, in which the capture of thin shear layers require the use of small cells. In this paper, a three-dimensional grid refinement technique is developed within the framework of hybrid recursive regularized lattice Boltzmann method (HRR-LBM) for compressible high-speed flows, which is an efficient collide-stream-type method on a compact D3Q19 stencil. The proposed method is successfully assessed considering several test cases, namely, an isentropic vortex propagating through transition interface, shock-vortex interaction with intersection between grid refinement interface and shock corrugation, and transonic flows over three-dimensional DLR-M6 wing with seven levels of grid refinement.
Y. Feng, S. Guo, J. Jacob, P. Sagaut. Grid refinement in the three-dimensional hybrid recursive regularized lattice Boltzmann method for compressible aerodynamics. Physical Review E , American Physical Society (APS), 2020, 101 (6), pp.063302. ⟨10.1103/PhysRevE.101.063302⟩. ⟨hal-03228997⟩
Simon Gsell, Etienne Loiseau, Umberto D’ortona, Annie Viallat, Julien Favier. Hydrodynamic model of directional ciliary-beat organization in human airways. Scientific Reports, Nature Publishing Group, 2020, 10 (8405), ⟨10.1038/s41598-020-64695-w⟩. ⟨hal-02614711⟩ Plus de détails...
In the lung, the airway surface is protected by mucus, whose transport and evacuation is ensured through active ciliary beating. the mechanisms governing the long-range directional organization of ciliary beats, required for effective mucus transport, are much debated. Here, we experimentally show on human bronchial epithelium reconstituted in-vitro that the dynamics of ciliary-beat orientation is closely connected to hydrodynamic effects. To examine the fundamental mechanisms of this self-organization process, we build a two-dimensional model in which the hydrodynamic coupling between cilia is provided by a streamwise-alignment rule governing the local orientation of the ciliary forcing. The model reproduces the emergence of the mucus swirls observed in the experiments. The predicted swirl sizes, which scale with the ciliary density and mucus viscosity, are in agreement with in-vitro measurements. A transition from the swirly regime to a long-range unidirectional mucus flow allowing effective clearance occurs at high ciliary density and high mucus viscosity. In the latter case, the mucus flow tends to spontaneously align with the bronchus axis due to hydrodynamic effects.
Simon Gsell, Etienne Loiseau, Umberto D’ortona, Annie Viallat, Julien Favier. Hydrodynamic model of directional ciliary-beat organization in human airways. Scientific Reports, Nature Publishing Group, 2020, 10 (8405), ⟨10.1038/s41598-020-64695-w⟩. ⟨hal-02614711⟩
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-02524483⟩ Plus de détails...
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-02524483⟩
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-03251615⟩ Plus de détails...
This work concerns the wind-driven resuspension in a narrow marine channel and the risk of transport of contaminated bottom sediments in a wide brackish lagoon in the context of a planned anthropogenic infrastructure (with forced convection, by pumping sea water). It is based on the modelling and 3D numerical simulation of salinity, current distributions and bottom shear stress (BSS). The goal is to demonstrate that, even for narrow channels of a few tens of meter of width, a wind of 10-20 m/s is sufficient to create intensive currents, to resuspend muddy bottom sediments and transport polluted sediments downstream. Several model scenarios are considered for such wind speeds in two dominant and opposite wind directions, for a channel whose bottom sediments are mainly constituted of fine particles, typically 85% of mud and 15% of fine sand. It is known that finer sediments usually play an important role to transport contaminants (due to larger surface area of smaller particles). Our main results concern the bottom shear stress along such a long and narrow channel; namely the Rove channel which confluences the Etang de Berre lagoon, and for which a project of forced current circulation is planned by pumping sea water. Our numerical results show that the mobility threshold can be easily overpassed for the muddy sediments in the Rove channel. For a bottom roughness of 5 μm (coarse silt) and a wind speed of 20 m/s, BSS can reach 0.18 N/m 2 for the N-NW wind in the median part of the channel, and even 0.21 N/m 2 in one enlargement for the S-SE wind, while BSS cr is about 0.1 N/m 2. We conclude that these local winds can permit floc erosion and even surface erosion of fine sediments in the Rove channel. Concerning the resuspension of muddy sediments, our results are consistent with the experimental study presented by Carlin et al. (2016) for a windy shallow lagoon. They are also consistent with the conclusion of Mengual et al. (2017), from erodimetry experiment for estuarine sediments, that the sediment behaves like a pure mud if the percentage of the mud fraction is more than 70%, and that the critical BSS for mobility of such bed sediments is of the order of 0.1 N/m 2. Such a lower critical BSS when the mixture is muddier is opposite to trends most often published.
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-03251615⟩
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-03251615⟩ Plus de détails...
This work concerns the wind-driven resuspension in a narrow marine channel and the risk of transport of contaminated bottom sediments in a wide brackish lagoon in the context of a planned anthropogenic infrastructure (with forced convection, by pumping sea water). It is based on the modelling and 3D numerical simulation of salinity, current distributions and bottom shear stress (BSS). The goal is to demonstrate that, even for narrow channels of a few tens of meter of width, a wind of 10-20 m/s is sufficient to create intensive currents, to resuspend muddy bottom sediments and transport polluted sediments downstream. Several model scenarios are considered for such wind speeds in two dominant and opposite wind directions, for a channel whose bottom sediments are mainly constituted of fine particles, typically 85% of mud and 15% of fine sand. It is known that finer sediments usually play an important role to transport contaminants (due to larger surface area of smaller particles). Our main results concern the bottom shear stress along such a long and narrow channel; namely the Rove channel which confluences the Etang de Berre lagoon, and for which a project of forced current circulation is planned by pumping sea water. Our numerical results show that the mobility threshold can be easily overpassed for the muddy sediments in the Rove channel. For a bottom roughness of 5 μm (coarse silt) and a wind speed of 20 m/s, BSS can reach 0.18 N/m 2 for the N-NW wind in the median part of the channel, and even 0.21 N/m 2 in one enlargement for the S-SE wind, while BSS cr is about 0.1 N/m 2. We conclude that these local winds can permit floc erosion and even surface erosion of fine sediments in the Rove channel. Concerning the resuspension of muddy sediments, our results are consistent with the experimental study presented by Carlin et al. (2016) for a windy shallow lagoon. They are also consistent with the conclusion of Mengual et al. (2017), from erodimetry experiment for estuarine sediments, that the sediment behaves like a pure mud if the percentage of the mud fraction is more than 70%, and that the critical BSS for mobility of such bed sediments is of the order of 0.1 N/m 2. Such a lower critical BSS when the mixture is muddier is opposite to trends most often published.
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-03251615⟩
Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. Consistent vortex initialization for the athermal lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (4), ⟨10.1103/PhysRevE.101.043306⟩. ⟨hal-03229006⟩ Plus de détails...
A barotropic counterpart of the well-known convected vortex test case is rigorously derived from the Euler equations along with an athermal equation of state. Starting from a given velocity distribution corresponding to an intended flow recirculation, the athermal counterpart of the Euler equations are solved to obtain a consistent density field. The present initialization is assessed on a standard lattice Boltzmann solver based on the D2Q9 lattice. Compared to the usual isentropic initialization, a much lower spurious relaxation toward the targeted solution is observed, which is due to the spatial resolution rather than approximated macroscopic quantities. The amplitude of the spurious waves can be further reduced by including an off-equilibrium part in the initial distribution functions.
Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. Consistent vortex initialization for the athermal lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (4), ⟨10.1103/PhysRevE.101.043306⟩. ⟨hal-03229006⟩
Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. Consistent vortex initialization for the athermal lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (4), ⟨10.1103/PhysRevE.101.043306⟩. ⟨hal-02892501⟩ Plus de détails...
A barotropic counterpart of the well-known convected vortex test case is rigorously derived from the Euler equations along with an athermal equation of state. Starting from a given velocity distribution corresponding to an intended flow recirculation, the athermal counterpart of the Euler equations are solved to obtain a consistent density field. The present initialization is assessed on a standard lattice Boltzmann solver based on the D2Q9 lattice. Compared to the usual isentropic initialization, a much lower spurious relaxation toward the targeted solution is observed, which is due to the spatial resolution rather than approximated macroscopic quantities. The amplitude of the spurious waves can be further reduced by including an off-equilibrium part in the initial distribution functions.
Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. Consistent vortex initialization for the athermal lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (4), ⟨10.1103/PhysRevE.101.043306⟩. ⟨hal-02892501⟩
Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. Consistent vortex initialization for the athermal lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (4), ⟨10.1103/PhysRevE.101.043306⟩. ⟨hal-02892501⟩ Plus de détails...
A barotropic counterpart of the well-known convected vortex test case is rigorously derived from the Euler equations along with an athermal equation of state. Starting from a given velocity distribution corresponding to an intended flow recirculation, the athermal counterpart of the Euler equations are solved to obtain a consistent density field. The present initialization is assessed on a standard lattice Boltzmann solver based on the D2Q9 lattice. Compared to the usual isentropic initialization, a much lower spurious relaxation toward the targeted solution is observed, which is due to the spatial resolution rather than approximated macroscopic quantities. The amplitude of the spurious waves can be further reduced by including an off-equilibrium part in the initial distribution functions.
Gauthier Wissocq, Jean-François Boussuge, Pierre Sagaut. Consistent vortex initialization for the athermal lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (4), ⟨10.1103/PhysRevE.101.043306⟩. ⟨hal-02892501⟩
T. Lyubimova, A. Lepikhin, Ya. Parshakova, C. Gualtieri, S. Lane, et al.. Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers. Journal of Applied Mechanics and Technical Physics, Springer Verlag, 2020, 60 (7), pp.1220-1227. ⟨10.1134/S0021894419070083⟩. ⟨hal-02989585⟩ Plus de détails...
At present, a significant weakening of the intensity of transverse mixing at the confluence of large rivers, which is observed in a number of cases, is widely discussed. Since the observed features of the confluence of large watercourses are not only of research interest but also of significant economic importance associated with the characteristics of water management at these water bodies, a large number of works are devoted to their study. Water resources management requires measures for the organization of water use which can be rational only under the understanding of processes occurring in water basins. To explain the phenomenon of suppression of the transverse mixing, which is interesting and important from the point of view of ecology, a wide range of hypotheses is proposed, up to the negation of turbulence in rivers. One of the possible mechanisms for explaining the suppression of transversal mixing can be the presence of transverse circulation manifesting itself as Prandtl’s secondary flows of the second kind. The characteristic velocity of these circulation flows is very small and difficult to measure directly by instruments; however, in our opinion, they can significantly complicate the transverse mixing at the confluence. The proposed hypothesis is tested in computational experiments in the framework of the three-dimensional formulation for dimensions of a real water object at the mouth of the Vishera River where it meets the Kama. Calculations demonstrate that, at sufficiently large flow rates, the two waters practically do not mix in the horizontal direction throughout the depth over long distances from the confluence. It has been found that a two-vortex flow is formed downstream the confluence, which just attenuates the mixing; the fluid motion in the vortices is such that, near the free surface, the fluid moves from the banks to the middle of the riverbed.
T. Lyubimova, A. Lepikhin, Ya. Parshakova, C. Gualtieri, S. Lane, et al.. Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers. Journal of Applied Mechanics and Technical Physics, Springer Verlag, 2020, 60 (7), pp.1220-1227. ⟨10.1134/S0021894419070083⟩. ⟨hal-02989585⟩
Journal: Journal of Applied Mechanics and Technical Physics
Simon Gsell, Umberto d'Ortona, Julien Favier. Multigrid dual-time-stepping lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (2), ⟨10.1103/PhysRevE.101.023309⟩. ⟨hal-02573156⟩ Plus de détails...
The lattice Boltzmann method often involves small numerical time steps due to the acoustic scaling (i.e., scaling between time step and grid size) inherent to the method. In this work, a second-order dual-time-stepping lattice Boltzmann method is proposed in order to avoid any time-step restriction. The implementation of the dual time stepping is based on an external source in the lattice Boltzmann equation, related to the time derivatives of the macroscopic flow quantities. Each time step is treated as a pseudosteady problem. The convergence rate of the steady lattice Boltzmann solver is improved by implementing a multigrid method. The developed solver is based on a two-relaxation time model coupled to an immersed-boundary method. The reliability of the method is demonstrated for steady and unsteady laminar flows past a circular cylinder, either fixed or towed in the computational domain. In the steady-flow case, the multigrid method drastically increases the convergence rate of the lattice Boltzmann method. The dual-time-stepping method is able to accurately reproduce the unsteady flows. The physical time step can be freely adjusted; its effect on the simulation cost is linear, while its impact on the accuracy follows a second-order trend. Two major advantages arise from this feature. (i) Simulation speed-up can be achieved by increasing the time step while conserving a reasonable accuracy. A speed-up of 4 is achieved for the unsteady flow past a fixed cylinder, and higher speed-ups are expected for configurations involving slower flow variations. Significant additional speed-up can also be achieved by accelerating transients. (ii) The choice of the time step allows us to alter the range of simulated timescales. In particular, increasing the time step results in the filtering of undesired pressure waves induced by sharp geometries or rapid temporal variations, without altering the main flow dynamics. These features may be critical to improve the efficiency and range of applicability of the lattice Boltzmann method.
Simon Gsell, Umberto d'Ortona, Julien Favier. Multigrid dual-time-stepping lattice Boltzmann method. Physical Review E , American Physical Society (APS), 2020, 101 (2), ⟨10.1103/PhysRevE.101.023309⟩. ⟨hal-02573156⟩
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, Elsevier, 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, Elsevier, 2020, 254, pp.107375. ⟨10.1016/j.cpc.2020.107375⟩. ⟨hal-02613709⟩
T. Lyubimova, A. Lepikhin, Ya Parshakova, C. Gualtieri, S. Lane, et al.. Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers. Journal of Applied Mechanics and Technical Physics, Springer Verlag, 2020, 60 (7), pp.1220-1227. ⟨10.1134/S0021894419070083⟩. ⟨hal-03231839⟩ Plus de détails...
At present, a significant weakening of the intensity of transverse mixing at the confluence of large rivers, which is observed in a number of cases, is widely discussed. Since the observed features of the confluence of large watercourses are not only of research interest but also of significant economic importance associated with the characteristics of water management at these water bodies, a large number of works are devoted to their study. Water resources management requires measures for the organization of water use which can be rational only under the understanding of processes occurring in water basins. To explain the phenomenon of suppression of the transverse mixing, which is interesting and important from the point of view of ecology, a wide range of hypotheses is proposed, up to the negation of turbulence in rivers. One of the possible mechanisms for explaining the suppression of transversal mixing can be the presence of transverse circulation manifesting itself as Prandtl’s secondary flows of the second kind. The characteristic velocity of these circulation flows is very small and difficult to measure directly by instruments; however, in our opinion, they can significantly complicate the transverse mixing at the confluence. The proposed hypothesis is tested in computational experiments in the framework of the three-dimensional formulation for dimensions of a real water object at the mouth of the Vishera River where it meets the Kama. Calculations demonstrate that, at sufficiently large flow rates, the two waters practically do not mix in the horizontal direction throughout the depth over long distances from the confluence. It has been found that a two-vortex flow is formed downstream the confluence, which just attenuates the mixing; the fluid motion in the vortices is such that, near the free surface, the fluid moves from the banks to the middle of the riverbed.
T. Lyubimova, A. Lepikhin, Ya Parshakova, C. Gualtieri, S. Lane, et al.. Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers. Journal of Applied Mechanics and Technical Physics, Springer Verlag, 2020, 60 (7), pp.1220-1227. ⟨10.1134/S0021894419070083⟩. ⟨hal-03231839⟩
Journal: Journal of Applied Mechanics and Technical Physics
S. Guo, Yongliang Feng, Jérôme Jacob, F. Renard, Pierre Sagaut. An efficient lattice Boltzmann method for compressible aerodynamics on D3Q19 lattice. Journal of Computational Physics, Elsevier, 2020, 418, pp.109570. ⟨10.1016/j.jcp.2020.109570⟩. ⟨hal-03232070⟩ Plus de détails...
An efficient lattice Boltzmann (LB) model relying on a hybrid recursive regularization (HRR) collision operator on D3Q19 stencil is proposed for the simulation of three-dimensional high-speed compressible flows in both subsonic and supersonic regimes. An improved thermal equilibrium distribution function on D3Q19 lattice is derived to reduce the complexity of correcting terms. A simple shock capturing scheme and an upwind biased discretization of correction terms are implemented for supersonic flows with shocks. Mass and momentum equations are recovered by an efficient streaming, collision and forcing process on D3Q19 lattice. Then a non-conservative formulation of the entropy evolution equation is used, that is solved using a finite volume method. The proposed method is assessed considering the simulation of i) 2D isentropic vortex convection, ii) 3D non-isothermal acoustic pulse, iii) 2D supersonic flow over a bump, iv) 3D shock explosion in a box, v) 2D vortex interaction with shock wave, vi) 2D laminar flows over a flat plate at Ma of 0.5, 1.0 and 1.5.
S. Guo, Yongliang Feng, Jérôme Jacob, F. Renard, Pierre Sagaut. An efficient lattice Boltzmann method for compressible aerodynamics on D3Q19 lattice. Journal of Computational Physics, Elsevier, 2020, 418, pp.109570. ⟨10.1016/j.jcp.2020.109570⟩. ⟨hal-03232070⟩
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, Elsevier, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-03232146⟩ Plus de détails...
The partially averaged Navier-Stokes (PANS) model, proposed in Girimaji (2006), allows to simulate turbulent flows either in RANS, LES or DNS mode. The PANS model includes f k which denotes the ratio of modeled to total kinetic energy. In RANS, f k = 1 while in DNS it tends to zero. In the present study we propose an improved formulation for f k based on the H-equivalence introduced by Friess et al. (2015). In this formulation the expression of f k is derived to mimic Improved Delayed Detached Eddy Simulation (IDDES). This new formulation behaves in a very similar way as IDDES, even though the two formulations use different mechanisms to separate modeled and resolved scales. They show very similar performance in separated flows as well as in attached boundary layers. In particular, the novel formulation is able to (i) treat attached boundary layers as properly as IDDES, and (ii) "detect" laminar initial/boundary conditions, in which case it enforces RANS mode. Furthermore, it is found that the new formulation is numerically more stable than IDDES.
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, Elsevier, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-03232146⟩
Journal: International Journal of Heat and Fluid Flow
Sylvia Wilhelm, Jérôme Jacob, Pierre Sagaut. A New Explicit Algebraic Wall Model for LES of Turbulent Flows Under Adverse Pressure Gradient. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2020, 106 (1), pp.1-35. ⟨10.1007/s10494-020-00181-7⟩. ⟨hal-03231798⟩ Plus de détails...
A new explicit algebraic wall law for the Large Eddy Simulation of flows with adverse pressure gradient is proposed. This new wall law, referred as adverse pressure gradient power law (APGPL), is developed starting from the power-law of Werner and Wengle (Turbulent Shear Flows, vol 8, Springer, New York, pp 155-168, 1993) in order to mimic an implicit non-equilibrium log-law based on Afzal's law (Afzal, IUTAM Symposium on Asymptotic Methods for Turbulent Shear Flows at High Reynolds Numbers, Kluwer Academic Publishers, Bochum, pp 95-118, 1996). No iterative method is needed for the evaluation of the wall shear stress from the APGPL contrary to the majority of models available in the literature. The APGPL model relies on the definition of three modes: the equilibrium power-law is used in regions of no or favourable pressure gradient, the APGPL is used in regions of adverse pressure gradient, and no wall model is used in separated flow regions. This model is assessed via Large Eddy Simulations of flows involving adverse pressure gradient and boundary layer separation using the Lattice Boltzmann Method on uniform nested grids. The flow around a clean and iced NACA23012 airfoil at Reynolds numberRe=1.88 x 10(6) and the flow over the LAGOON landing gear at Re=1.59x10(6) are considered. Results are found in good agreement with those obtained by the non-equilibrium log-law and experimental and numerical data available in the literature.
Sylvia Wilhelm, Jérôme Jacob, Pierre Sagaut. A New Explicit Algebraic Wall Model for LES of Turbulent Flows Under Adverse Pressure Gradient. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2020, 106 (1), pp.1-35. ⟨10.1007/s10494-020-00181-7⟩. ⟨hal-03231798⟩
A Gineau, E. Longatte, D. Lucor, P. Sagaut. Macroscopic model of fluid structure interaction in cylinder arrangement using theory of mixture. Computers and Fluids, Elsevier, 2020, 202, pp.104499. ⟨10.1016/j.compfluid.2020.104499⟩. ⟨hal-03251640⟩ Plus de détails...
In the framework of the theory of mixture, the dynamic behaviour of solid cylinder bundles submitted to external hydrodynamic load exerted by surrounding viscous fluid flow is described. Mass conservation and momentum balance formulated on an elementary domain made of a given volume of mixture give rise to a system of coupled equations governing solid space-averaged displacement, fluid velocity and pressure provided that near-wall hydrodynamic load on each vibrating cylinder is expressed as a function of both fluid and solid space-averaged velocity fields. Then, the ability of the macroscopic model to reproduce over time an averaged flow surrounding vibrating cylinders in a large array in the context of small magnitude displacements is pointed out. Numerical solutions obtained on a two-dimensional configuration involving an array of several hundreds of cylinders subjected to an impulsional load are compared to those provided by averaged well-resolved microscopic-scale solutions. The relative error is less than 3% in terms of displacement magnitude and 5% for frequency delay. The proposed macroscopic model does not include any assumption on relative effect contributions to mechanical exchanges occurring in the full domain. Therefore it features interesting properties in terms of fluid solid interaction prediction capabilities. Moreover it contributes to a significant gain in terms of computational time and resources. Further developments are now required in order to extent the formulation to large magnitude displacements including three-dimensional effects. This could be recommended for investigations on fuel assembly vibration risk assessment in Pressure Water, Fast Breeder reactors at a whole core scale or any other large-scale mechanical system involving some kind of periodic geometry.
A Gineau, E. Longatte, D. Lucor, P. Sagaut. Macroscopic model of fluid structure interaction in cylinder arrangement using theory of mixture. Computers and Fluids, Elsevier, 2020, 202, pp.104499. ⟨10.1016/j.compfluid.2020.104499⟩. ⟨hal-03251640⟩
