- Directeur de l'Ecole Doctorale 353 - Sciences pour l'ingénieur
- Membre du Comité Scientifique de l'EUROFUSION - Theory and Advanced Simulation Coordination
- Président du Comité thématique Physique théorique et plasma au GENCI
- Editorial board Journal of Engineering
Activités
Ecoulements en rotation: Taylor-Couette, rotor-stator, éclatement tourbillonnaire, couches limites,...
Plasmas de tokamak: Modélisation, transport turbulent, plasma de bord
Méthodes numériques d'ordre élevé
Publications scientifiques au M2P2
2021
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⟩
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⟩
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⟩
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⟩
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⟩
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⟩
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 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. Cartier-Michaud, D. Galassi, Ph Ghendrih, P. Tamain, F. Schwander, et al.. A posteriori error estimate in fluid simulations of turbulent edge plasmas for magnetic fusion in tokamak using the data mining iPoPe method. Physics of Plasmas, American Institute of Physics, 2020. ⟨hal-02613800⟩ Plus de détails...
Progressing towards more reliable numerical solutions in the simulation of plasma for magnetic confinement fusion has become a critical issue for the success of the ITER operation. This requires developing rigorous and efficient methods of verification of the numerical simulations in any relevant flow regimes of the operation. The paper introduces a new formulation of the PoPe 1 method, namely the independent Projection on Proper elements method (iPoPe) to quantify the numerical error by performing a data-driven identification of the mathematical model from the simulation outputs. Based on a statistical postprocessing of the outputs database, the method provides a measure of the error by estimating the distance between the (numerical) effective and (analytical) theoretical weights of each operator implemented in the mathematical model. The efficiency of the present method is illustrated on turbulent edge plasma simulations based on a drift-reduced Braginskii fluid model in realistic magnetic geometries. Results show the effective order of the numerical method in these multiscale flow regimes as well as the values of the plasma parameters which can be safely simulated with respect to a given discretization. In this sense, the method goes one step further than the Method of Manufactured Solution (MMS 2-4), recently introduced in fusion, and provides an efficient verification procedure of the numerical simulations in any regimes, including turbulent ones that could be generalized to other scientific domains.
T. Cartier-Michaud, D. Galassi, Ph Ghendrih, P. Tamain, F. Schwander, et al.. A posteriori error estimate in fluid simulations of turbulent edge plasmas for magnetic fusion in tokamak using the data mining iPoPe method. Physics of Plasmas, American Institute of Physics, 2020. ⟨hal-02613800⟩
R. Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios. Nuclear Fusion, IOP Publishing, 2019, 59 (10), pp.106019. ⟨10.1088/1741-4326/ab3005⟩. ⟨hal-02468022⟩ Plus de détails...
The SOLEDGE-EIRENE edge plasma code provides solutions for particle and energy transport in the plasma edge within complex and realistic 2D geometries (Bufferand et al 2015 Nucl. Fusion 55 053025). In this work, divertor detachment is simulated on HL-2M alternative magnetic configurations in pure deuterium plasma. Starting from a typical HL-2M low single-null configuration, the snowflake plus (SF+) and snowflake minus (SF-) configurations have then been investigated. Detachment of the outer target is studied in these configurations during plasma density ramps controlled by a fueling source, with constant input power and constant radial transport coefficients. Some typical characteristics of detachment, like threshold, depth and upstream window of detachment are investigated. In the three geometries, detachment onset and evolution with upstream plasma density is characterized by the gradual displacement of a radiation front from the outer target to the main X-point, as observed in experiments. It is found that, whatever the detachment in terms of particle, momentum or power dissipation, the detachment threshold is dominated primarily by the geometrical structure of the divertor plate and does not exhibit dependence on the magnetic configuration of the diverted plasma volume. In particular, the parallel connection length in the divertor is not found to affect the detachment threshold, in contrast with simple expectations from the two-point model, but in agreement with experimental findings.
R. Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios. Nuclear Fusion, IOP Publishing, 2019, 59 (10), pp.106019. ⟨10.1088/1741-4326/ab3005⟩. ⟨hal-02468022⟩
F. Nespoli, P. Tamain, N. Fedorczak, G. Ciraolo, D. Galassi, et al.. 3D structure and dynamics of filaments in turbulence simulations of WEST diverted plasmas. Nuclear Fusion, IOP Publishing, 2019. ⟨hal-02364554⟩ Plus de détails...
We study the effect of a diverted magnetic geometry on edge plasma turbulence, focusing on the three-dimensional structure and dynamics of filaments, also called blobs, in simulations of the WEST tokamak, featuring a primary and secondary X-point. For this purpose, in addition to classical analysis techniques, we apply here a novel fully 3D Blob Recognition And Tracking (BRAT) algorithm, allowing for the first time to resolve the three-dimensional structure and dynamics of the blobs in a turbulent 3D plasma featuring a realistic magnetic geometry. The results are tested against existing theoretical scalings of blob velocity [Myra et al, Physics of Plasmas 2006]. The complementary analysis of the 3D structure of the filaments shows how they disconnect from the divertor plate in the vicinity of the X-points, leading to a transition from a sheath-connected regime to the ideal-interchange one. Furthermore, the numerical results show non-negligible effects of the turbulent background plasma: approximately half of the detected filaments are involved in mutual interactions, eventually resulting in negative radial velocities, and a fraction of the filaments is generated by turbulence directly below the X-point.
F. Nespoli, P. Tamain, N. Fedorczak, G. Ciraolo, D. Galassi, et al.. 3D structure and dynamics of filaments in turbulence simulations of WEST diverted plasmas. Nuclear Fusion, IOP Publishing, 2019. ⟨hal-02364554⟩
G. Ciraolo, A. Thin, H. Bufferand, J. Bucalossi, N. Fedorczak, et al.. First modeling of strongly radiating WEST plasmas with SOLEDGE-EIRENE. Nuclear Materials and Energy, Elsevier, 2019, 20, pp.100685. ⟨10.1016/j.nme.2019.100685⟩. ⟨hal-02468035⟩ Plus de détails...
We present first results of SOLEDGE-EIRENE modeling a strongly radiating plasma in the WEST tokamak. Using measurements from a reciprocating Langmuir probe we have determined the SOLEDGE input parameters, i.e. separatrix density at outboard midplane and radial transport coefficients typical of L-mode plasma. We have performed deuterium plasma simulations with presence of oxygen, injected from the core boundary into the simulation domain. The comparison between the radiated power measured from the bolometry in the divertor region and the one computed from SOLEDGE simulations seems to indicate a concentration of oxygen of about 2%. Moreover we have obtained good agreement between simulation results and experimental measurements on electron density and electron temperature profiles at the outer strike point. First qualitative analysis of spectroscopic synthetic diagnostic on D-alpha signals is also presented.
G. Ciraolo, A. Thin, H. Bufferand, J. Bucalossi, N. Fedorczak, et al.. First modeling of strongly radiating WEST plasmas with SOLEDGE-EIRENE. Nuclear Materials and Energy, Elsevier, 2019, 20, pp.100685. ⟨10.1016/j.nme.2019.100685⟩. ⟨hal-02468035⟩
R Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of alternative divertor configuration on plasma detachment: pure Deuterium simulations with SolEdge2D-EIRENE edge transport code for HL-2M scenario. Nuclear Fusion, 2019. ⟨hal-02370418⟩ Plus de détails...
The SOLEDGE-EIRENE edge plasma code provides solutions for particle & energy transport in the plasma edge within complex and realistic 2D geometries [1]. In this work, divertor detachment is simulated on the HL-2M alternative magnetic configurations in pure Deuterium plasma. Starting from typical HL-2M low single-null (SN) configuration, the snowflake plus (SF+) and snowflake minus (SF-) configurations have been investigated. Detachment of the outer target is studied in these configurations during plasma density ramps controlled by a fueling source, at constant input power and constant radial transport coefficients. Some typical characteristics of detachment, like threshold, depth and upstream window of detachment are investigated. In the three geometries, detachment onset and evolution with upstream plasma density is characterized by the gradual displacement of a radiation front from the outer target to the main X-point, as observed in experiments. It is found that, whatever the detachment in terms of particle, momentum or power dissipation, the detachment threshold is dominated primarily by the geometrical structure of divertor plate and it does not exhibit dependence on the magnetic configuration of the diverted plasma volume. In particular, the parallel connection length in the divertor is not found to affect the detachment threshold, in contrast with simple expectations from the 2-point model, but in agreement with experimental findings.
R Mao, N. Fedorczak, G. Ciraolo, H. Bufferand, Y. Marandet, et al.. Impact of alternative divertor configuration on plasma detachment: pure Deuterium simulations with SolEdge2D-EIRENE edge transport code for HL-2M scenario. Nuclear Fusion, 2019. ⟨hal-02370418⟩
S. Baschetti, H. Bufferand, G. Ciraolo, N. Fedorczak, P. Ghendrih, et al.. A κ − ε model for plasma anomalous transport in tokamaks: closure via the scaling of the global confinement. Nuclear Materials and Energy, Elsevier, 2019, 19, pp.200-204. ⟨10.1016/j.nme.2019.02.032⟩. ⟨hal-02177039⟩ Plus de détails...
A reduced model for radial anomalous transport of plasma in tokamaks, inspired by the Reynolds-Averaged Navier-Stokes (RANS) approach, is presented assuming diffusion as governing mechanism. In order to self-consistently calculate transport coefficients, an empirical equation is built for the turbulent kinetic energy and the system is closed via the scaling law of global confinement. In such way the SOL width appears to recover experimental dependencies with respect to machine parameters and interestingly, when the model is implemented in a 2D transport code for a realistic study-case, mean fields retrieve some features already observed in 1st-principle turbulent codes.
S. Baschetti, H. Bufferand, G. Ciraolo, N. Fedorczak, P. Ghendrih, et al.. A κ − ε model for plasma anomalous transport in tokamaks: closure via the scaling of the global confinement. Nuclear Materials and Energy, Elsevier, 2019, 19, pp.200-204. ⟨10.1016/j.nme.2019.02.032⟩. ⟨hal-02177039⟩
Julien Denis, J. Bucalossi, G. Ciraolo, Etienne Hodille, B. Pégourié, et al.. Dynamic modelling of local fuel inventory and desorption in the whole tokamak vacuum vessel for auto-consistent plasma-wall interaction simulations. Nuclear Materials and Energy, Elsevier, 2019, 19, pp.550-557. ⟨10.1016/j.nme.2019.03.019⟩. ⟨hal-02902060⟩ Plus de détails...
An extension of the SolEdge2D-EIRENE code package, named D-WEE, has been developed to add the dynamics of thermal desorption of hydrogen isotopes from the surface of plasma facing materials. To achieve this purpose, D-WEE models hydrogen isotopes implantation, transport and retention in those materials. Before launching auto-consistent simulation (with feedback of D-WEE on SolEdge2D-EIRENE), D-WEE has to be initialised to ensure a realistic wall behaviour in terms of dynamics (pumping or fuelling areas) and fuel content. A methodology based on modelling is introduced to perform such initialisation. A synthetic plasma pulse is built from consecutive SolEdge2D-EIRENE simulations. This synthetic pulse is used as a plasma background for the D-WEE module. A sequence of plasma pulses is simulated with D-WEE to model a tokamak operation. This simulation enables to extract at a desired time during a pulse the local fuel inventory and the local desorption flux density which could be used as initial condition for coupled plasma-wall simulations. To assess the relevance of the dynamic retention behaviour obtained in the simulation, a confrontation to post-pulse experimental pressure measurement is performed. Such confrontation reveals a qualitative agreement between the temporal pressure drop obtained in the simulation and the one observed experimentally. The simulated dynamic retention during the consecutive pulses is also studied.
Julien Denis, J. Bucalossi, G. Ciraolo, Etienne Hodille, B. Pégourié, et al.. Dynamic modelling of local fuel inventory and desorption in the whole tokamak vacuum vessel for auto-consistent plasma-wall interaction simulations. Nuclear Materials and Energy, Elsevier, 2019, 19, pp.550-557. ⟨10.1016/j.nme.2019.03.019⟩. ⟨hal-02902060⟩
Giorgio Giorgiani, H. Bufferand, G. Ciraolo, Eric Serre, P. Tamain. A magnetic-field independent approach for strongly anisotropic equations arising plasma-edge transport simulations. Nuclear Materials and Energy, Elsevier, 2019, 19, pp.340-345. ⟨10.1016/j.nme.2019.03.002⟩. ⟨hal-02177048⟩ Plus de détails...
A [Summary] The control of the power exhaust in tokamaks is still an open issue for the future fusion operations. The heat loads on divertor and limiter PFCs is largely determined by the physics of the Scrape-Off Layer (SOL), and therefore it depends mainly on the geometry of the magnetic surfaces and on the geometry of wall components. A better characterization of the heat exhaust mechanisms requires therefore to improve the capabilities of the transport codes in terms of geometrical description of the wall components and in terms of the description of the magnetic geometry. The possibility of dealing with evolving magnetic configurations becomes also critical: during start-up or control operations, for example, the evolution of particles and heat fluxes is little known, although being critical for the safety of the machine. Hence, among the new capabilities of future transport codes will be the possibility of accurately describe the reactor chamber, and the flexibility with respect the magnetic configuration. In particular, avoiding expensive re-meshing of the computational domain in case of evolving equilibrium is mandatory. In order to fulfill these requirements, in this work a fluid solver based on non-aligned discretization is used to solve the plasma-edge transport equations for density, momentum and energies. Preliminary tests on non-structured meshes and realistic geometries/physical parameters show the pertinency of this novel approach.
Giorgio Giorgiani, H. Bufferand, G. Ciraolo, Eric Serre, P. Tamain. A magnetic-field independent approach for strongly anisotropic equations arising plasma-edge transport simulations. Nuclear Materials and Energy, Elsevier, 2019, 19, pp.340-345. ⟨10.1016/j.nme.2019.03.002⟩. ⟨hal-02177048⟩
Davide Galassi, Guido Ciraolo, Patrick Tamain, Hugo Bufferand, Philippe Ghendrih, et al.. Tokamak Edge Plasma Turbulence Interaction with Magnetic X-Point in 3D Global Simulations. Fluids, MDPI, 2019, 4 (1), pp.50. ⟨10.3390/fluids4010050⟩. ⟨hal-02176982⟩ Plus de détails...
Turbulence in the edge plasma of a tokamak is a key actor in the determination of the confinement properties. The divertor configuration seems to be beneficial for confinement, suggesting an effect on turbulence of the particular magnetic geometry introduced by the X-point. Simulations with the 3D fluid turbulence code TOKAM3X are performed here to evaluate the impact of a diverted configuration on turbulence in the edge plasma, in an isothermal framework. The presence of the X-point is found, locally, to affect both the shape of turbulent structures and the amplitude of fluctuations, in qualitative agreement with recent experimental observations. In particular, a quiescent region is found in the divertor scrape-off layer (SOL), close to the separatrix. Globally, a mild transport barrier spontaneously forms in the closed flux surfaces region near the separatrix, differently from simulations in limiter configuration. The effect of turbulence-driven Reynolds stress on the formation of the barrier is found to be weak by dedicated simulations, while turbulence damping around the X-point seems to globally reduce turbulent transport on the whole flux surface. The magnetic shear is thus pointed out as a possible element that contributes to the formation of edge transport barriers.
Davide Galassi, Guido Ciraolo, Patrick Tamain, Hugo Bufferand, Philippe Ghendrih, et al.. Tokamak Edge Plasma Turbulence Interaction with Magnetic X-Point in 3D Global Simulations. Fluids, MDPI, 2019, 4 (1), pp.50. ⟨10.3390/fluids4010050⟩. ⟨hal-02176982⟩
Marco Martins Afonso, Philippe Meliga, Eric Serre. Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step. Fluids, MDPI, 2019, 4 (1), pp.33. ⟨10.3390/fluids4010033⟩. ⟨hal-02176963⟩ Plus de détails...
With the aim of providing a first step in the quest for a reduction of the aerodynamic drag on the rear-end of a car, we study the phenomena of separation and reattachment of an incompressible flow by focusing on a specific aerodynamic geometry, namely a backward-slanted step at 25 circle of inclination. The ensuing recirculation bubble provides the basis for an analytical and numerical investigation of streamwise-streak generation, lift-up effect, and turbulent-wake and Kelvin-Helmholtz instabilities. A linear stability analysis is performed, and an optimal control problem with a steady volumic forcing is tackled by means of a variational formulation, adjoint methods, penalization schemes, and an orthogonalization algorithm. Dealing with the transient growth of spanwise-periodic perturbations, and inspired by the need of physically-realizable disturbances, we finally provide a procedure attaining a kinetic-energy maximal gain on the order of 106, with respect to the power introduced by the external forcing.
Marco Martins Afonso, Philippe Meliga, Eric Serre. Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step. Fluids, MDPI, 2019, 4 (1), pp.33. ⟨10.3390/fluids4010033⟩. ⟨hal-02176963⟩
D.M. Fan, Y. Marandet, P. Tamain, H. Bufferand, G. Ciraolo, et al.. Effect of turbulent fluctuations on neutral particles transport with the TOKAM3X-EIRENE turbulence code. Nuclear Materials and Energy, Elsevier, 2019, 18, pp.105-110. ⟨10.1016/j.nme.2018.12.011⟩. ⟨hal-02176529⟩ Plus de détails...
The effect of turbulent fluctuations on the transport of neutral particles (atoms, molecules) in tokamak plasmas is investigated with the 3D global turbulence code TOKAM3X-EIRENE in limiter geometry. The statistical properties of turbulent fields relevant to this work are discussed, including the recycling flux. The neutral particle transport is recalculated on the mean field plasma, and compared to the mean neutral particle density/flows obtained from the turbulent simulation, so as to assess the effects of the fluctuations, in particular on the ionization balance. The latter effects are remarkably modest in the simulation presented here, but are expected to become more and more pronounced as the high recycling regime is approached, in particular because the plasma temperature becomes low enough so that ionization is strongly non-linear. However, the turbulent fluctuations in the SOL do have a substantial effect on the neutral densities on the low field side of the limiter, including in the confined plasma. These effects are traced back to non-linearities in the plasma flux at the wall, and the fluctuations in the latter are identified as an important contributor both to neutral particle density fluctuations and to deviations from mean neutral particle density/flows in the turbulent simulation with respect to the same quantities recalculated on the mean plasma fields.
D.M. Fan, Y. Marandet, P. Tamain, H. Bufferand, G. Ciraolo, et al.. Effect of turbulent fluctuations on neutral particles transport with the TOKAM3X-EIRENE turbulence code. Nuclear Materials and Energy, Elsevier, 2019, 18, pp.105-110. ⟨10.1016/j.nme.2018.12.011⟩. ⟨hal-02176529⟩
H. Bufferand, P. Tamain, S. Baschetti, J. Bucalossi, G. Ciraolo, et al.. Three-dimensional modelling of edge multi-component plasma taking into account realistic wall geometry. Nuclear Materials and Energy, Elsevier, 2019, 18, pp.82-86. ⟨10.1016/j.nme.2018.11.025⟩. ⟨hal-02176521⟩ Plus de détails...
H. Bufferand, P. Tamain, S. Baschetti, J. Bucalossi, G. Ciraolo, et al.. Three-dimensional modelling of edge multi-component plasma taking into account realistic wall geometry. Nuclear Materials and Energy, Elsevier, 2019, 18, pp.82-86. ⟨10.1016/j.nme.2018.11.025⟩. ⟨hal-02176521⟩
J. Soler, F. Schwander, G Giorgiani, J Liandrat, P Tamain, et al.. A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain. Journal of Computational Physics, Elsevier, 2019, ⟨10.1016/j.jcp.2019.109093⟩. ⟨hal-02477007⟩ Plus de détails...
Highly anisotropic elliptic problems occur in many physical models that need to be solved numerically. A direction of dominant diffusion is thus introduced (called here parallel direction) along which the diffusion coefficient is several orders larger of magnitude than in the perpendicular one. In this case, finite-difference methods based on misaligned stencils are generally not designed to provide an optimal discretization, and may lead the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. This paper proposes an original scheme using non-aligned Cartesian grids and interpolations aligned along a parallel diffusion direction. Here, this direction is assumed to be supported by a divergence-free vector field which never vanishesand it is supposed to be stationary in time. Based on the Support Operator Method (SOM), the self-adjointness property of the parallel diffusion operator is maintained on the discrete level. Compared with existing methods, the present formulation further guarantees the conservativity of the fluxes in both parallel and perpendicular directions. In addition, when the flow intercepts a boundary in the parallel direction, an accurate discretization of the boundary condition is presented that avoids the uncertainties of extrapolated far ghost points classicaly used and ensures a better accuracy of the solution. Numerical tests based on manufactured solutions show the method is able to provide accurate and stable numerical approximations in both periodic and bounded domains with a drastically reduced number of degrees of freedom with respect to non-aligned approaches.
J. Soler, F. Schwander, G Giorgiani, J Liandrat, P Tamain, et al.. A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain A new conservative finite-difference scheme for anisotropic elliptic problems in bounded domain. Journal of Computational Physics, Elsevier, 2019, ⟨10.1016/j.jcp.2019.109093⟩. ⟨hal-02477007⟩
F. Nespoli, H. Bufferand, M. Valentinuzzi, N. Fedorczak, G. Ciraolo, et al.. Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma. Nuclear Materials and Energy, Elsevier, 2019, 18, pp.29-34. ⟨10.1016/j.nme.2018.11.026⟩. ⟨hal-02176505⟩ Plus de détails...
The edge and scrape-off layer (SOL) plasma of the inter-ELM phase of an H-mode discharge from the TCV tokamak is modeled with the transport code SolEdge2D-EIRENE (Bufferand et al. Nuclear Fusion 55 (2015)). The numerical simulations, in presence and in absence of C impurities sputtered from the first wall, are presented and compared with the experiments, finding an overall good agreement. The application of the standard two-point model to the simulation results leads to an apparent momentum gain along the divertor leg. A two-fluid two-point model featuring thermally decoupled ions and electrons is introduced and applied to the simulation results, overcoming this apparent discrepancy.
F. Nespoli, H. Bufferand, M. Valentinuzzi, N. Fedorczak, G. Ciraolo, et al.. Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma. Nuclear Materials and Energy, Elsevier, 2019, 18, pp.29-34. ⟨10.1016/j.nme.2018.11.026⟩. ⟨hal-02176505⟩
Giorgio Giorgiani, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Frédéric Schwander, et al.. A hybrid discontinuous Galerkin method for tokamak edge plasma simulations in global realistic geometry. Journal of Computational Physics, Elsevier, 2018, 374, pp.515-532. ⟨10.1016/j.jcp.2018.07.028⟩. ⟨hal-02114246⟩ Plus de détails...
Progressing toward more accurate and more efficient numerical codes forthe simulation of transport and turbulence in the edge plasma of tokamaks,we propose in this work a new hybrid discontinous Galerkin solver. Basedon 2D advection-diffusion conservation equations for the ion density and theparticle flux in the direction parallel to the magnetic field, the code simulatesplasma transport in the poloidal section of tokamaks, including the open fieldlines of the Scrape-off Layer (SOL) and the closed field lines of the core re-gion. The spatial discretization is based on a high-order hybrid DG schemeon unstructured meshes, which provides an arbitrary high-order accuracywhile reducing considerably the number of coupled degrees of freedom witha local condensation process. A discontinuity sensor is employed to identifycritical elements and regularize the solution with the introduction of artificialdiffusion. Based on a finite-element discretization, not constrained by a flux-aligned mesh, the code is able to describe plasma facing components of anycomplex shape using Bohm boundary conditions and to simulate the plasmain versatile magnetic equilibria, possibly extended up to the center. Nu-merical tests using a manufacturated solution show appropriate convergenceorders when varying independently the number of elements or the degree ofinterpolation. Validation is performed by benchmarking the code with thewell-referenced edge transport code SOLEDGE2D (Bufferandet al.2013,2015 [1, 2]) in the WEST geometry. Final numerical experiments show thecapacity of the code to deal with low-diffusion solutions.
Giorgio Giorgiani, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Frédéric Schwander, et al.. A hybrid discontinuous Galerkin method for tokamak edge plasma simulations in global realistic geometry. Journal of Computational Physics, Elsevier, 2018, 374, pp.515-532. ⟨10.1016/j.jcp.2018.07.028⟩. ⟨hal-02114246⟩
Philippe Ghendrih, Y. Asahi, E. Caschera, G. Dif-Pradalier, P. Donnel, et al.. Generation and dynamics of SOL corrugated profiles. Journal of Physics: Conference Series, IOP Publishing, 2018, 1125, pp.012011. ⟨10.1088/1742-6596/1125/1/012011⟩. ⟨hal-02196677⟩ Plus de détails...
The staircase transport regime reported in kinetic simulations of plasma turbulent transport in magnetic confinement is recovered with a simple 2D fluid model allowing for reduced damping of the zonal flows. Some of the complex dynamics of the kinetic zonation regime are recovered but the pattern of the corrugation appears to be sinusoidal with a characteristic scale comparable to that of turbulence modes with largest spectral energy, in contrast to regimes observed in global and flux-driven kinetic simulations. Enhanced zonal flows govern both an overall reduction of the SOL width and a gradual steepening of the gradients with distance to the separatrix.
Philippe Ghendrih, Y. Asahi, E. Caschera, G. Dif-Pradalier, P. Donnel, et al.. Generation and dynamics of SOL corrugated profiles. Journal of Physics: Conference Series, IOP Publishing, 2018, 1125, pp.012011. ⟨10.1088/1742-6596/1125/1/012011⟩. ⟨hal-02196677⟩
Eunok Yim, J.-M. Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor–stator cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018, 848, pp.631 - 647. ⟨10.1017/jfm.2018.239⟩. ⟨hal-02116221⟩ Plus de détails...
The transition to turbulence in the rotating disk boundary layer is investigated in a closed cylindrical rotor-stator cavity via direct numerical simulation (DNS) and linear stability analysis (LSA). The mean flow in the rotor boundary layer is qualitatively similar to the von Karman self-similarity solution. The mean velocity profiles, however, slightly depart from theory as the rotor edge is approached. Shear and centrifugal effects lead to a locally more unstable mean flow than the self-similarity solution, which acts as a strong source of perturbations. Fluctuations start rising there, as the Reynolds number is increased, eventually leading to an edge-driven global mode, characterized by spiral arms rotating counter-clockwise with respect to the rotor. At larger Reynolds numbers, fluctuations form a steep front, no longer driven by the edge, and followed downstream by a saturated spiral wave, eventually leading to incipient turbulence. Numerical results show that this front results from the superposition of several elephant front-forming global modes, corresponding to unstable azimuthal wavenumbers m, in the range m is an element of [32, 78 ]. The spatial growth along the radial direction of the energy of these fluctuations is quantitatively similar to that observed experimentally. This superposition of elephant modes could thus provide an explanation for the discrepancy observed in the single disk configuration, between the corresponding spatial growth rates values measured by experiments on the one hand, and predicted by LSA and DNS performed in an azimuthal sector, on the other hand.
Eunok Yim, J.-M. Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor–stator cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018, 848, pp.631 - 647. ⟨10.1017/jfm.2018.239⟩. ⟨hal-02116221⟩
L Valade, A. Ekedahl, P Ghendrih, Y. Sarazin, Y. Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02196679⟩ Plus de détails...
Hot spot generation by Lower Hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D-1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function with an island structure in the suprathermal part at the phase velocity of the external electrostatic drive. The non-linear features enhance the plasma response driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function with extent up to one thermal velocity is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of 1
L Valade, A. Ekedahl, P Ghendrih, Y. Sarazin, Y. Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02196679⟩
Laurent Valade, Annika Ekedahl, Philippe Ghendrih, Yanick Sarazin, Yuuichi Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02116142⟩ Plus de détails...
Hotspot generation by lower-hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D-1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function. An island structure is formed in the suprathermal part at the phase velocity of the external electrostatic drive. The non-linear features enhance the plasma response, driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function, with extent reaching one thermal velocity, is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of the small-scale features generated by the LH launchers, which are responsible for the interaction with the cold electrons. This mechanism can trigger hotspot generation further in the scrape-off layer than otherwise expected.
Laurent Valade, Annika Ekedahl, Philippe Ghendrih, Yanick Sarazin, Yuuichi Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02116142⟩
Guido Ciraolo, Hugo Bufferand, Pierfrancesco Di Cintio, Philippe Ghendrih, Stefano Lepri, et al.. Fluid and kinetic modelling for non-local heat transport in magnetic fusion devices. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.457-464. ⟨10.1002/ctpp.201700222⟩. ⟨hal-02113953⟩ Plus de détails...
In order to improve the presently used ad hoc flux limiter treatment of parallel heat flux transport in edge plasma fluid codes, here, we consider a generalized version of the Fourier law implementing a non-local kernel for the heat flux computation. The Bohm boundary condition at the wall is recovered, introducing a volumetric loss term representing the contribution of suprathermal particles to the energy out flux. As expected, this contribution is negligible in the strongly collisional regime, while it becomes more and more dominant for marginally and low-collisional regimes. In the second part of the paper, we consider a kinetic approach where collisions are considered using the multi-particle collision algorithm. Kinetic simulation results at medium and low collisionality are also reported.
Guido Ciraolo, Hugo Bufferand, Pierfrancesco Di Cintio, Philippe Ghendrih, Stefano Lepri, et al.. Fluid and kinetic modelling for non-local heat transport in magnetic fusion devices. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.457-464. ⟨10.1002/ctpp.201700222⟩. ⟨hal-02113953⟩
Serafina Baschetti, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Optimization of turbulence reduced model free parameters based on L-mode experiments and 2D transport simulations. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.511-517. ⟨10.1002/ctpp.201700163⟩. ⟨hal-02111708⟩ Plus de détails...
In this paper, a κ−ϵ transport model is presented as a turbulence reduction tool for a typical ohmic L‐mode discharge plasma in a divertor‐configurated tokamak. Taking a Tokamak à configuration variable (TCV) study case, a feedback loop procedure is performed using the SolEdge2D code to acquire plasma diffusivity at the outer mid‐plane. The κ−ϵ model is calibrated through its free parameters with the aim of recovering the diffusivity calculated in the feedback procedure. Finally, it is shown that the model can self‐consistently calculate diffusivity in the whole domain, recovering the poloidal asymmetries due to interchange instabilities.
Serafina Baschetti, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Optimization of turbulence reduced model free parameters based on L-mode experiments and 2D transport simulations. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.511-517. ⟨10.1002/ctpp.201700163⟩. ⟨hal-02111708⟩
Dongmei Fan, Yannick Marandet, Patrick Tamain, Hugo Bufferand, Guido Ciraolo, et al.. Self-consistent coupling of the three-dimensional fluid turbulence code TOKAM3X and the kinetic neutrals code EIRENE. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.490-496. ⟨10.1002/ctpp.201700216⟩. ⟨hal-02114027⟩ Plus de détails...
The three-dimensional (3D) turbulence code TOKAM3X-EIRENE, coupling the 3D non-isothermal version of TOKAM3X to the EIRENE Monte Carlo solver has been developed with the ability to simulate self-consistently the interactions between large-scale flows and turbulence both in limited and diverted plasmas, including recycling. This is especially important for diverted plasmas, where neutrals play a key role and where the recycling source is strongly dominant. The code package relies on the same interface as the Soledge2D-EIRENE code, which retains state-of-the-art plasma-wall interaction, as well as atomic and molecular physics. In this paper, we present the first results obtained in WEST divertor geometry, in laminar mode, with the aim of verifying the new code package. The divertor density regimes are recovered, and the code results are shown to be consistent with the results of the two-point model, thus opening the way for turbulent simulations.
Dongmei Fan, Yannick Marandet, Patrick Tamain, Hugo Bufferand, Guido Ciraolo, et al.. Self-consistent coupling of the three-dimensional fluid turbulence code TOKAM3X and the kinetic neutrals code EIRENE. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.490-496. ⟨10.1002/ctpp.201700216⟩. ⟨hal-02114027⟩
Matteo Valentinuzzi, Giorgio Giorgiani, Yannick Marandet, Hugo Bufferand, Guido Ciraolo, et al.. Fluid description of neutral particles in divertor regimes in WEST. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.710-717. ⟨10.1002/ctpp.201700211⟩. ⟨hal-02116176⟩ Plus de détails...
A new neutral fluid code has been developed as a necessary step towards a hybrid fluid/kinetic neutral model, to be used in ITER or DEMO simulations, where part of the divertor will be very collisional for neutrals. The neutral fluid code, which is able to handle complex geometries in view of the coupling to Soledge2D, is tested on plasma backgrounds obtained by Soledge2D‐Eirene in WEST geometry, for different divertor regimes, and is found to be in fair agreement with the kinetic Monte Carlo solver Eirene. The differences are due to the simplifications introduced in the fluid model and to the fact that a fluid description is not fully valid in these cases.
Matteo Valentinuzzi, Giorgio Giorgiani, Yannick Marandet, Hugo Bufferand, Guido Ciraolo, et al.. Fluid description of neutral particles in divertor regimes in WEST. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.710-717. ⟨10.1002/ctpp.201700211⟩. ⟨hal-02116176⟩
Hugo Bufferand, Guido Ciraolo, Pierfrancesco Di Cintio, Nicolas Fedorczak, Philippe Ghendrih, et al.. Non-local heat flux application for scrape-off layer plasma. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.563-569. ⟨10.1002/ctpp.201700162⟩. ⟨hal-02112673⟩ Plus de détails...
The non-local expression proposed by Luciani-Mora-Virmont is implemented in a one dimensional fluid model for the scrape-off layer. Analytical solutions for heat equation are discussed as well as the impact of sheath boundary conditions on the continuity of the temperature profile. The non-local heat flux is compared to the Spitzer-Härm heat flux for different collisionality. KEYWORDS heat conduction, non-local transport, plasma physics 1 INTRODUCTION At the entrance of the scrape-off layer, the plasma collisionality í µí¼ ⋆ defined as the ratio between the field line length and collision mean free path is found to be of order unity. Despite this low collisionality, the tokamak edge plasma modelling relies mostly on the fluid approach and collisional closures that are theoretically only valid at high collisionality. Departure between Braginskii fluid description and kinetic modelling has been highlighted, particularly an underestimation of temperature gradient by the fluid approach. [1] Several kinetic corrections have been proposed to improve the plasma description at intermediate collisionality. [2-5] In this contribution, we investigate kinetic corrections to the local Spitzer-Härm (Braginskii) closure for the heat flux; more precisely, we focus on applying the non-local expression for the heat flux proposed by Luciani-Mora-Virmont [6] to scrape-off layer physics. In particular, we adapt boundary conditions and implement the non-local expression into a 1D hydrodynamic model for the scrape-off layer.
Hugo Bufferand, Guido Ciraolo, Pierfrancesco Di Cintio, Nicolas Fedorczak, Philippe Ghendrih, et al.. Non-local heat flux application for scrape-off layer plasma. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.563-569. ⟨10.1002/ctpp.201700162⟩. ⟨hal-02112673⟩
Nicolas Nace, Patrick Tamain, Camille Baudoin, Hugo Bufferand, Guido Ciraolo, et al.. Impact of safety factor and magnetic shear profiles on edge turbulence in circular limited geometry. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.497-504. ⟨10.1002/ctpp.201700174⟩. ⟨hal-02115405⟩ Plus de détails...
The impact of magnetic configuration on edge turbulence properties in circular limiter geometry is investigated using TOKAM3X, a three-dimensional (3D), first-principle, fluid code for edge plasma. The theoretical spatial tilting of magnetic shear on turbulence fluctuations is recovered. Magnetic shear is found to generate or enhance poloidal high/low field sides (HFS/LFS) and up/down asymmetries. A simulation mimicking the impact of an X-point on circular limiter geometry leads to the formation of two transport barriers that are stable in time, thus leading to the improvement of core particle confinement and to reduction of radial turbulent transport. The magnetic shear, which also strongly enhances the E × B shear, is responsible for the barrier formation.
Nicolas Nace, Patrick Tamain, Camille Baudoin, Hugo Bufferand, Guido Ciraolo, et al.. Impact of safety factor and magnetic shear profiles on edge turbulence in circular limited geometry. Contributions to Plasma Physics, Wiley-VCH Verlag, 2018, 58 (6-8), pp.497-504. ⟨10.1002/ctpp.201700174⟩. ⟨hal-02115405⟩
Eunok Yim, J.-M Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018, 836, pp.43-71. ⟨10.1017/jfm.2017.771⟩. ⟨hal-02121890⟩ Plus de détails...
This paper proposes a resolution to the conundrum of the roles of convective and absolute instability in transition of the rotating-disk boundary layer. It also draws some comparison with swept-wing flows. Direct numerical simulations based on the incompressible Navier–Stokes equations of the flow over the surface of a rotating disk with modelled roughness elements are presented. The rotating-disk flow has been of particular interest for stability and transition research since the work by Lingwood (J. Fluid Mech., vol. 299, 1995, pp. 17–33) where an absolute instability was found. Here stationary disturbances develop from roughness elements on the disk and are followed from the linear stage, growing to saturation and finally transitioning to turbulence. Several simulations are presented with varying disturbance amplitudes. The lowest amplitude corresponds approximately to the experiment by Imayama et al. (J. Fluid Mech., vol. 745, 2014a, pp. 132–163). For all cases, the primary instability was found to be convectively unstable, and secondary modes were found to be triggered spontaneously while the flow was developing. The secondary modes further stayed within the domain, and an explanation for this is a proposed globally unstable secondary instability. For the low-amplitude roughness cases, the disturbances propagate beyond the threshold for secondary global instability before becoming turbulent, and for the high-amplitude roughness cases the transition scenario gives a turbulent flow directly at the critical Reynolds number for the secondary global instability. These results correspond to the theory of Pier (J. Engng Maths, vol. 57, 2007, pp. 237–251) predicting a secondary absolute instability. In our simulations, high temporal frequencies were found to grow with a large amplification rate where the secondary global instability occurred. For smaller radial positions, low-frequency secondary instabilities were observed, tripped by the global instability. The transition to turbulence in the rotating disk boundary layer is investigated in a closed cylindrical rotor-stator cavity via direct numerical simulation (DNS) and linear stability analysis (LSA). The mean flow in the rotor boundary layer is qualitatively similar to the von Kármán self-similarity solution. The mean velocity profiles, however, slightly depart from theory as the rotor edge is approached. Shear and centrifugal effects lead to a locally more unstable mean flow than the self-similarity solution, which acts as a strong source of perturbations. Fluctuations start rising there, as the Reynolds number is increased, eventually leading to an edge-driven global mode, characterized by spiral arms rotating counterclockwise with respect to the rotor. At larger Reynolds numbers, fluctuations form a steep front, no longer driven by the edge, and followed downstream by a saturated spiral wave, eventually leading to incipient turbulence. Numerical results show that this front results from the superposition of several elephant front-forming global modes, corresponding to unstable azimuthal wavenumbers m, in the range m ∈ [32, 78]. The spatial growth along the radial direction of the energy of these fluctuations is quantitatively similar to that observed experimentally. This superposition of elephant modes could thus provide an explanation for the discrepancy observed in the single disk configuration, between the corresponding spatial growth rates values measured by experiments on the one hand, and predicted by LSA and DNS performed in an azimuthal sector, on the other hand.
Eunok Yim, J.-M Chomaz, Denis Martinand, Eric Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018, 836, pp.43-71. ⟨10.1017/jfm.2017.771⟩. ⟨hal-02121890⟩
Giorgio Giorgiani, Hervé Guillard, Boniface Nkonga, Eric Serre. A stabilized Powell–Sabin finite-element method for the 2D Euler equations in supersonic regime. Computer Methods in Applied Mechanics and Engineering, Elsevier, 2018, 340, pp.216-235. ⟨10.1016/j.cma.2018.05.032⟩. ⟨hal-01865708⟩ Plus de détails...
In this paper a Powell–Sabin finite-element (PS-FEM) scheme is presented for the solution of the 2D Euler equations in supersonic regime. The spatial discretization is based on PS splines, that are piecewise quadratic polynomials with a global continuity, defined on conforming triangulations. Some geometrical issues related to the practical construction of the PS elements are discussed, in particular, the generation of the control triangles and the imposition of the boundary conditions. A stabilized formulation is considered, and a novel shock-capturing technique in the context of continuous finite-elements is proposed to reduce oscillations around the discontinuity, and compared with the classical technique proposed by Tezduyar and Senga (2006). The code is verified using manufactured solutions and validated using two challenging numerical examples, which allows to evaluate the performance of the PS discretization in capturing the shocks.
Giorgio Giorgiani, Hervé Guillard, Boniface Nkonga, Eric Serre. A stabilized Powell–Sabin finite-element method for the 2D Euler equations in supersonic regime. Computer Methods in Applied Mechanics and Engineering, Elsevier, 2018, 340, pp.216-235. ⟨10.1016/j.cma.2018.05.032⟩. ⟨hal-01865708⟩
Journal: Computer Methods in Applied Mechanics and Engineering
Dominique Morvan. Comprendre et prévenir les feux de végétation. Université Grenoble Alpes. Encyclopédie de l’Environnement, 2018. ⟨hal-01678486⟩ Plus de détails...
H. Riahi, Marcello Meldi, Julien Favier, Eric Serre, Eric Goncalves da Silva. A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows. Journal of Computational Physics, Elsevier, 2018, 374, pp.361-383. ⟨10.1016/j.jcp.2018.07.033⟩. ⟨hal-01859760⟩ Plus de détails...
The development of an improved new IBM method is proposed in the present article. This method roots in efficient proposals developed for the simulation of incompressible flows, and it is expanded for compressible configurations. The main feature of this model is the integration of a pressure-based correction of the IBM forcing which is analytically derived from the set of dynamic equations. The resulting IBM method has been integrated in various flow solvers available in the CFD platform OpenFOAM. A rigorous validation has been performed considering different test cases of increasing complexity. The results have been compared with a large number of references available in the literature of experimental and numerical nature. This analysis highlights numerous favorable characteristics of the IBM method, such as precision, flexibility and computational cost efficiency.
H. Riahi, Marcello Meldi, Julien Favier, Eric Serre, Eric Goncalves da Silva. A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows. Journal of Computational Physics, Elsevier, 2018, 374, pp.361-383. ⟨10.1016/j.jcp.2018.07.033⟩. ⟨hal-01859760⟩
Thomas Cartier-Michaud, Philippe Ghendrih, Guilhem Dif-Pradalier, Xavier Garbet, Virginie Grandgirard, et al.. Verification of turbulent simulations using PoPe: quantifying model precision and numerical error with data mining of simulation output. Journal of Physics: Conference Series, IOP Publishing, 2018, 1125, pp.012005. ⟨10.1088/1742-6596/1125/1/012005⟩. ⟨hal-02196674⟩ Plus de détails...
Verification of a 1D-1V kinetic code with the PoPe method [1] is presented. Investigation of the impact of reducing the precision of the numerical scheme is analysed by following 3 indicators of the physics solved by the code, namely the plasma response to an external high frequency electric field wave. The response of the distribution function in the vicinity of the particle-wave resonance is found to be most sensitive to the resolution. Consistently, a rapid growth of the error indicator determined with PoPe is observed. However, no critical value of this indicator allowing us to retain the physics in a situation of degraded precision could be observed. The response of the amplitude of the electric potential fluctuations is characterised by a transient growth followed by a plateau. It is found that the loss of this plateau is governed by the resolution in v-space, but due to the generation of a symmetry in the problem rather than to errors in the numerical scheme. The analysis of the transient indicates that the growth rate of the amplitude of the electric potential is very robust down to very low resolution, step in velocity of 2 thermal velocities. However, a transition prior to this resolution, with step 0.5 thermal velocity, can be identified corresponding to a PoPe indicator of order zero, namely for errors of order 100 %.
Thomas Cartier-Michaud, Philippe Ghendrih, Guilhem Dif-Pradalier, Xavier Garbet, Virginie Grandgirard, et al.. Verification of turbulent simulations using PoPe: quantifying model precision and numerical error with data mining of simulation output. Journal of Physics: Conference Series, IOP Publishing, 2018, 1125, pp.012005. ⟨10.1088/1742-6596/1125/1/012005⟩. ⟨hal-02196674⟩
Eunok Yim, J.-M Chomaz, D Martinand, E Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018. ⟨hal-02927579⟩ Plus de détails...
The transition to turbulence in the rotating disk boundary layer is investigated in a closed cylindrical rotor-stator cavity via direct numerical simulation (DNS) and linear stability analysis (LSA). The mean flow in the rotor boundary layer is qualitatively similar to the von Kármán self-similarity solution. The mean velocity profiles, however, slightly depart from theory as the rotor edge is approached. Shear and centrifugal effects lead to a locally more unstable mean flow than the self-similarity solution, which acts as a strong source of perturbations. Fluctuations start rising there, as the Reynolds number is increased, eventually leading to an edge-driven global mode, characterized by spiral arms rotating counterclockwise with respect to the rotor. At larger Reynolds numbers, fluctuations form a steep front, no longer driven by the edge, and followed downstream by a saturated spiral wave, eventually leading to incipient turbulence. Numerical results show that this front results from the superposition of several elephant front-forming global modes, corresponding to unstable azimuthal wavenumbers m, in the range m ∈ [32, 78]. The spatial growth along the radial direction of the energy of these fluctuations is quantitatively similar to that observed experimentally. This superposition of elephant-modes could thus provide an explanation for the discrepancy observed in the single disk configuration, between the corresponding spatial growth rates values measured by experiments on the one hand, and predicted by LSA and DNS performed in an azimuthal sector, on the other hand.
Eunok Yim, J.-M Chomaz, D Martinand, E Serre. Transition to turbulence in the rotating disk boundary layer of a rotor-stator cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018. ⟨hal-02927579⟩
Denis Martinand, Eric Serre, Richard M. Lueptow. Linear and weakly nonlinear analyses of cylindrical Couette flow with axial and radial flows. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2017, 824, pp.438 - 476. ⟨10.1017/jfm.2017.351⟩. ⟨hal-01592948⟩ Plus de détails...
Extending previous linear stability analyses of the instabilities developing in permeable Taylor-Couette-Poiseuille flows where axial and radial throughflows are superimposed on the usual Taylor-Couette flow, we further examine the linear behaviour and expand the analysis to consider the weakly nonlinear behaviour of convective-type instabilities by means of the derivation of the fifth-order amplitude equation together with direct numerical simulations. Special attention is paid to the influence of the radius ratio eta = r(in)/r(out), and particularly to wide gaps (small eta) and how they magnify the effects of the radial flow. The instabilities take the form of pairs of counter-rotating toroidal vortices superseded by helical ones as the axial flow is increased. Increasing the radial inflow draws these vortices near the inner cylinder, where they shrink relative to the annular gap, when this gap is wide. Strong axial and radial flows in a narrow annular gap lead to a very large azimuthal wavenumber with steeply sloped helical vortices. Strong radial outflow in a wide annular gap results in very large helical vortices. The analytical and numerical saturated vortices match quite well. In addition, radial inflows or outflows can turn the usually supercritical bifurcation from laminar to vortical flow into a subcritical one. The radial flow above which this change occurs decreases as the radius ratio eta decreases. A practical motivation for this weakly nonlinear analysis is found in modelling dynamic filtration devices, which rely on vortical instabilities to reduce the processes of accumulation on their membranes.
Denis Martinand, Eric Serre, Richard M. Lueptow. Linear and weakly nonlinear analyses of cylindrical Couette flow with axial and radial flows. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2017, 824, pp.438 - 476. ⟨10.1017/jfm.2017.351⟩. ⟨hal-01592948⟩
P. Tamain, C. Colin, L. Colas, C. Baudoin, G. Ciraolo, et al.. Numerical analysis of the impact of an RF sheath on the Scrape-Off Layer in 2D and 3D turbulence simulations. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.1171 - 1177. ⟨10.1016/j.nme.2016.12.022⟩. ⟨hal-01702267⟩ Plus de détails...
Motivated by Radio Frequency (RF) heating studies, the response of the plasma of tokamaks to the presence of a locally polarized limiter is studied. In a first part, we use the TOKAM3X 3D global edge turbulence code to analyse the impact of such biasing in a realistic geometry. Key features of experimental observations are qualitatively recovered, especially the extension of a potential and density perturbation on long, but finite, distances along connected field lines. The perturbation is also found to extend in the transverse direction. Both observations demonstrate the influence of perpendicular current loops on the plasma confirming the need for an accurate description in reduced models. In a second part, we use the TOKAM2D slab turbulence code to determine the validity of using a transverse Ohm's law for this purpose. Results indicate that a local Ohm's law with a constant and uniform perpendicular resistivity appears at least as an oversimplified description of perpendicular charge transport in a turbulent Scrape-Off Layer.
P. Tamain, C. Colin, L. Colas, C. Baudoin, G. Ciraolo, et al.. Numerical analysis of the impact of an RF sheath on the Scrape-Off Layer in 2D and 3D turbulence simulations. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.1171 - 1177. ⟨10.1016/j.nme.2016.12.022⟩. ⟨hal-01702267⟩
W.A. Gracias, P. Tamain, Eric Serre, R.A. Pitts, L. Garcia. The impact of magnetic shear on the dynamics of a seeded 3D filament in slab geometry. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.798 - 807. ⟨10.1016/j.nme.2017.02.022⟩. ⟨hal-01702187⟩ Plus de détails...
Seeded filament simulations are used to study blob dynamics with the state-of-the-art TOKAM3X fluid code in the scrape-off layer (SOL) using a slab geometry. The filamentary dynamics recovered with the code are compared with previously predicted analytical blob velocity scalings while also studying the effect of field line pitch angle on these dynamics and are found to be similar. The effect of changing magnetic topology on filamentary motion is also investigated. Magnetic shear is introduced in the model by the sudden and localised variation of field line pitch angle for a narrow radially located region constituting effectively a shearing zone. Three such shear zones are tested to see how they affect filament motion. Filaments are initialised radially upstream from the shear zone and recorded as they convect towards the far-SOL side. The lowest intensity shear zone allows many of the higher amplitude filaments to pass through after dampening them. On the other hand, the highest intensity shear zones prevent all filaments from progressing to the wall beyond the shear zone and, in certain cases for high density amplitude filaments, is able to generate a new filament downstream from the shear zone.
W.A. Gracias, P. Tamain, Eric Serre, R.A. Pitts, L. Garcia. The impact of magnetic shear on the dynamics of a seeded 3D filament in slab geometry. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.798 - 807. ⟨10.1016/j.nme.2017.02.022⟩. ⟨hal-01702187⟩
Y. Marandet, H. Bufferand, N. Nace, M. Valentinuzzi, G. Ciraolo, et al.. Towards a consistent modelling of plasma edge turbulence in mean field transport codes: Focus on sputtering and plasma fluctuations. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.931 - 934. ⟨10.1016/j.nme.2017.02.007⟩. ⟨hal-01702229⟩ Plus de détails...
Transport codes are the main workhorses for global edge studies and modern divertor design. These tools do not resolve turbulent fluctuations responsible for the bulk of cross-field transport in the Scrape-off Layer (SOL), and solve mean field equations instead. Turbulent fluxes are modelled by diffusive transport along the gradients of the mean fields. Improvements of this description, on the basis of approaches developed in computational fluid dynamics are discussed, broadening the outlook given in Bufferand et al. (2016) [10]. This contribution focuses on additional closure issues related to non-linearities in sources/sinks from plasma-wall interactions, here sputtered fluxes from the plasma facing components. “Fluctuation dressed” sputtering yields Yeff are introduced and calculated from turbulence simulations. Properly taking fluctuations into account is shown to lead to higher sputtering at sub-threshold energies compared to mean field predictions. As a first step towards an implementation in a transport code, the possibility of parametrizing Yeff in terms of the mean fields is tentatively investigated.
Y. Marandet, H. Bufferand, N. Nace, M. Valentinuzzi, G. Ciraolo, et al.. Towards a consistent modelling of plasma edge turbulence in mean field transport codes: Focus on sputtering and plasma fluctuations. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.931 - 934. ⟨10.1016/j.nme.2017.02.007⟩. ⟨hal-01702229⟩
Eddy Constant, Julien Favier, Marcello Meldi, Philippe Meliga, Eric Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers and Fluids, Elsevier, 2017, 157, pp.55 - 72. ⟨10.1016/j.compfluid.2017.08.001⟩. ⟨hal-01591562⟩ Plus de détails...
The present work proposes a modified Pressure-Implicit Split-Operator (PISO) solver integrating the recent Immersed Boundary Method (IBM) proposed by Pinelli et al. [1] in order to perform reliable simulations of incompressible flows around bluff bodies using the open source toolbox OpenFOAM version 2.2 (ESI-OpenCFD [2]). The (IBM) allows for a precise representation of fixed and moving solid obstacles embedded in the physical domain, using uniform or stretched Cartesian meshes. Owing to this feature, the maximum level of accuracy and scalability of the numerical solvers can be systematically achieved. An iterative scheme based on sub-iterations between (IBM) and pressure correction has been implemented in the native (PISO) solver of OpenFOAM. This allows one to use fast optimized Poisson solvers while satisfying simultaneously the divergence-free flow state and the no-slip condition at the body surface. To compute the divergence of the momentum equation (in the PISO loop) and the interpolation of the fluxes, we propose an hybrid calculation with an analytical resolution (using the kernel function equation) of the quantities involving the force term (singular quantities). A careful and original verification study has been carried out which allows to estimate three different errors related to the discretization and to the (IBM). Various 2D and 3D well-documented test cases of academic flows around fixed or moving cylinders have been simulated and carefully validated against existing data from the literature in a large range of Reynolds numbers, Re = 30 − 3900 and in the frame of DNS and DDES OpenFOAM native models.
Eddy Constant, Julien Favier, Marcello Meldi, Philippe Meliga, Eric Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers and Fluids, Elsevier, 2017, 157, pp.55 - 72. ⟨10.1016/j.compfluid.2017.08.001⟩. ⟨hal-01591562⟩
G. Ciraolo, H. Bufferand, J. Bucalossi, Ph. Ghendrih, P. Tamain, et al.. H-mode WEST tungsten divertor operation: deuterium and nitrogen seeded simulations with SOLEDGE2D-EIRENE. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.187 - 192. ⟨10.1016/j.nme.2016.12.025⟩. ⟨hal-01702237⟩ Plus de détails...
Simulations of WEST H-mode divertor scenarios have been performed with SOLEDGE2D-EIRENE edge plasma transport code, both for pure deuterium and nitrogen seeded discharge. In the pure deuterium case, a target heat flux of 8 MW/m2 is reached, but misalignment between heat and the particle outflux yields 50 eV plasma temperature at the target plates. With nitrogen seeding, the heat and particle outflux are observed to be aligned so that lower plasma temperatures at the target plates are achieved together with the required high heat fluxes. This change in heat and particle outflux alignment is analysed with respect to the role of divertor geometry and the impact of vertical vs horizontal target plates on neutrals spreading.
G. Ciraolo, H. Bufferand, J. Bucalossi, Ph. Ghendrih, P. Tamain, et al.. H-mode WEST tungsten divertor operation: deuterium and nitrogen seeded simulations with SOLEDGE2D-EIRENE. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.187 - 192. ⟨10.1016/j.nme.2016.12.025⟩. ⟨hal-01702237⟩
Davide Galassi, P. Tamain, C. Baudoin, H. Bufferand, G. Ciraolo, et al.. Flux expansion effect on turbulent transport in 3D global simulations. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.953 - 958. ⟨10.1016/j.nme.2017.01.008⟩. ⟨hal-01702255⟩ Plus de détails...
The flux expansion effect on the Scrape-Off Layer equilibrium is inspected through TOKAM3X 3D turbulence simulations. Three magnetic equilibria with analytically controlled flux expansion are built, representing respectively a positive, a null and a negative Shafranov shift. Turbulent E × B fluxes across flux surfaces show similar amplitudes and poloidal distributions in all cases. The ballooning nature of the interchange instability is recovered, with an enhancement of turbulence in the vicinity of the limiter, probably due to a Kelvin–Helmoltz instability. Interestingly, the poloidally averaged density decay length is found to be shorter almost by a factor 2 in the case of flux surfaces compressed at the low-field side midplane, with respect to the opposite case, indicating the presence of unfavorable conditions for the turbulent transport. The difference in the magnetic field line shape is pointed out as a mechanism which affects the turbulent transport across the flux surfaces. Indeed the unstable region has a larger parallel extension when flux expansion in the low-field side is larger. Moreover, the configuration with a lower magnetic shear at the low-field side midplane shows a more unstable behavior. The role of this parameter in turbulence stabilization is qualitatively evaluated. The difference in the distribution of transport along the parallel direction is shown to affect also the parallel flows, which are analyzed for the three proposed cases.
Davide Galassi, P. Tamain, C. Baudoin, H. Bufferand, G. Ciraolo, et al.. Flux expansion effect on turbulent transport in 3D global simulations. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.953 - 958. ⟨10.1016/j.nme.2017.01.008⟩. ⟨hal-01702255⟩
Congshan Zhuo, Pierre Sagaut. Acoustic multipole sources for the regularized lattice Boltzmann method: Comparison with multiple-relaxation-time models in the inviscid limit. Physical Review E , American Physical Society (APS), 2017, 95 (6), pp.063301. ⟨10.1103/PhysRevE.95.063301⟩. ⟨hal-01548424⟩ Plus de détails...
Congshan Zhuo, Pierre Sagaut. Acoustic multipole sources for the regularized lattice Boltzmann method: Comparison with multiple-relaxation-time models in the inviscid limit. Physical Review E , American Physical Society (APS), 2017, 95 (6), pp.063301. ⟨10.1103/PhysRevE.95.063301⟩. ⟨hal-01548424⟩
Alekseenko Elena, Bernard Roux. Submerged Aquatic Vegetation Restoration in Brackish Ecosystems Subject to Strong Winds and Coastal Jets. Oceanography & Fisheries Open access Journal, 2017, 2 (4), pp.555595. ⟨10.19080/OFOAJ.2017.02.555595⟩. ⟨hal-01813859⟩ Plus de détails...
The bottom shear stress (BSS) in a windy Mediterranean lagoon has been carefully investigated through numerical modelling. BSS maps have been obtained for the entire lagoon. The aim is to compare BSS with its critical value in the near shoreareas selected for SAV replanting which are subject to downwind coastal jets.
Alekseenko Elena, Bernard Roux. Submerged Aquatic Vegetation Restoration in Brackish Ecosystems Subject to Strong Winds and Coastal Jets. Oceanography & Fisheries Open access Journal, 2017, 2 (4), pp.555595. ⟨10.19080/OFOAJ.2017.02.555595⟩. ⟨hal-01813859⟩
Journal: Oceanography & Fisheries Open access Journal
Davide Galassi, P. Tamain, H. Bufferand, Guido Ciraolo, Ph. Ghendrih, et al.. Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry. Nuclear Fusion, IOP Publishing, 2017, 57 (3), pp.036029. ⟨10.1088/1741-4326/aa5332⟩. ⟨hal-01592945⟩ Plus de détails...
The poloidal asymmetries of parallel flows in edge plasmas are investigated by the 3D fluid turbulence code TOKAM3X. A diverted COMPASS-like magnetic equilibrium is used for the simulations. The measurements and simulations of parallel Mach numbers are compared, and exhibit good qualitative agreement. Small-scale turbulent transport is observed to dominate near the low field side midplane, even though it co-exists with significant large-scale cross-field fluxes. Despite the turbulent nature of the plasma in the divertor region, simulations show the low effectiveness of turbulence for the cross-field transport towards the private flux region. Nevertheless, a complex pattern of fluxes associated with the average field components are found to cross the separatrix in the divertor region. Large-scale and small-scale turbulent E x B transport, along with the del B drift, drive the asymmetries in parallel flows. A semian-alytical model based on mass and parallel momentum balances allows the poloidal drift effects on the asymmetry pattern to be evaluated. As in the experiments, a reversed B-T simulation provides a way of self-consistently separating the effects of turbulent transport and large-scale flows, which must be reversed for a reversed field. The large-scale contribution is found to be responsible for typically 50% of the effect on the Mach number, evaluated at the top of the machine. The presented picture shows the complex interplay between drifts and turbulence, underlining the necessity of a global approach to edge plasma modelling, including a self-consistent description of the turbulence.
Davide Galassi, P. Tamain, H. Bufferand, Guido Ciraolo, Ph. Ghendrih, et al.. Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry. Nuclear Fusion, IOP Publishing, 2017, 57 (3), pp.036029. ⟨10.1088/1741-4326/aa5332⟩. ⟨hal-01592945⟩
R.J.A. Howard, Eric Serre. Large eddy simulation in Code_Saturne of thermal mixing in a T junction with brass walls. International Journal of Heat and Fluid Flow, Elsevier, 2017, 63, pp.119 - 127. ⟨10.1016/j.ijheatfluidflow.2016.09.011⟩. ⟨hal-01592931⟩ Plus de détails...
Following on from Kuhn et al (2010) we study the capability of large eddy simulation with conjugate heat transfer to predict thermal fluctuations with thermal mixing. Wall functions are used to model the wall heat transfer. Comparison with experimental results show that the temperature variance on the outer skin of the solid is well predicted by the simulation. It is shown that the variance of thermal flux in the fluid closely maps the temperature variance at the outer boundary of the solid. Since the variance of thermal flux is closely related to the dissipation of temperature variance it can be concluded that the dissipation of temperature variance in the fluid is linked to temperature variance in the solid. Analysis of the equation of the temperature variance in the solid confirms this is indeed the case. It is the dissipation of temperature variance in the fluid that characterizes how the temperature variance penetrates the solid. Thus RANS modelling can be used to predict thermal variance in solids provided that there is an accurate model for the dissipation of temperature variance at the wall and an equation for the thermal variance in the solid is solved.
R.J.A. Howard, Eric Serre. Large eddy simulation in Code_Saturne of thermal mixing in a T junction with brass walls. International Journal of Heat and Fluid Flow, Elsevier, 2017, 63, pp.119 - 127. ⟨10.1016/j.ijheatfluidflow.2016.09.011⟩. ⟨hal-01592931⟩
Journal: International Journal of Heat and Fluid Flow
Hugo Bufferand, G. Ciraolo, P Di Cintio, N Fedorczak, Ph Ghendrih, et al.. Nonlocal heat flux application for Scrape-off Layer plasma. Contributions to Plasma Physics, Wiley-VCH Verlag, In press. ⟨hal-01655295⟩ Plus de détails...
The nonlocal expression proposed by Luciani-Mora-Virmont is implemented into a 1D fluid model for the scrape-off layer. Analytic solutions for heat equation are discussed as well as the impact of sheath boundary conditions on the continuity of the temperature profile. The nonlocal heat flux is compared to Spitzer-Härm heat flux for different collisionality.
Hugo Bufferand, G. Ciraolo, P Di Cintio, N Fedorczak, Ph Ghendrih, et al.. Nonlocal heat flux application for Scrape-off Layer plasma. Contributions to Plasma Physics, Wiley-VCH Verlag, In press. ⟨hal-01655295⟩
Hugo Bufferand, C Baudoin, J Bucalossi, G Ciraolo, J Denis, et al.. Implementation of drift velocities and currents in SOLEDGE2D-EIRENE. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.852-857. ⟨hal-01372986⟩ Plus de détails...
In order to improve cross-field transport description, drifts and currents have been implemented in SOLEDGE2D-EIRENE. The derivation of an equation for the electric potential is recalled. The resolution of current equation is tested in a simple slab case. WEST divertor simulations in forward-B and reverse-B fields are also discussed. A significant increase of ExB shear is observed in the forward-B configuration that could explain a favorable L-H transition in this case.
Hugo Bufferand, C Baudoin, J Bucalossi, G Ciraolo, J Denis, et al.. Implementation of drift velocities and currents in SOLEDGE2D-EIRENE. Nuclear Materials and Energy, Elsevier, 2017, 12, pp.852-857. ⟨hal-01372986⟩
Philippe Meliga, Olivier Cadot, Eric Serre. Experimental and Theoretical Sensitivity Analysis of Turbulent Flow Past a Square Cylinder. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2016, 97 (4, SI), pp.987-1015. ⟨10.1007/s10494-016-9755-0⟩. ⟨hal-01461791⟩ Plus de détails...
We assess experimentally and theoretically the ability of a small control cylinder to alter vortex shedding in turbulent flow past a square cylinder at R e = 22,000. Results are presented in terms of sensitivity maps showing the flow regions where the shedding frequency and amplitude are most affected by the control cylinder. Experimental results are obtained for a ratio 0.02 of the cylinder diameters, over an extended domain covering the wake, the shear layers and the free stream. The shedding frequency can be either decreased or increased, the largest effects being obtained placing the control cylinder at the outer edge of the detached shear layers (associated with frequency decrease) or upstream of the square cylinder (associated with frequency increase, in contrast with previous results obtained for a D-shaped geometry of the main cylinder). In contrast, the oscillation amplitude is rarely decreased, meaning that any variation of the shedding frequency comes at the expense of more intense vortex shedding. These findings are revisited in the frame of a theoretical, linear sensitivity analysis of the time-averaged mean flow, performed using adjoint methods in the frame of Reynolds-averaged Navier-Stokes modeling. We show that the retained approach carries valuable information in view of guiding efficient control strategy, as it allows identifying the main regions yielding either a decrease or an increase of the shedding frequency in striking agreement with the experiments. This is a tremendous timesaving in so far as the controlled states need not be computed, the overall computational cost being roughly that of computing the mean flow. In contrast, performing the sensitivity analysis on the underlying unstable steady state yields flawed predictions, hence stressing the need to encompass some level of mean coherent-coherent perturbations interaction in the linear model.
Philippe Meliga, Olivier Cadot, Eric Serre. Experimental and Theoretical Sensitivity Analysis of Turbulent Flow Past a Square Cylinder. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2016, 97 (4, SI), pp.987-1015. ⟨10.1007/s10494-016-9755-0⟩. ⟨hal-01461791⟩
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Davide Galassi, et al.. The TOKAM3X code for edge turbulence fluid simulations of tokamak plasmas in versatile magnetic geometries. Journal of Computational Physics, Elsevier, 2016, 321, pp.606-623. ⟨10.1016/j.jcp.2016.05.038⟩. ⟨hal-01461797⟩ Plus de détails...
The new code TOKAM3X simulates plasma turbulence in full torus geometry including the open field lines of the Scrape-off Layer (SOL) and the edge closed field lines region in the vicinity of the separatrix. Based on drift-reduced Braginskii equations, TOKAM3X is able to simulate both limited and diverted plasmas. Turbulence is flux driven by incoming particles from the core plasma and no scale separation between the equilibrium and the fluctuations is assumed so that interactions between large scale flows and turbulence are consistently treated. Based on a domain decomposition, specific numerical schemes are proposed using conservative finite-differences associated to a semi-implicit time advancement. The process computation is multi-threaded and based on MPI and OpenMP libraries. In this paper, fluid model equations are presented together with the proposed numerical methods. The code is verified using the manufactured solution technique and validated through documented simple experiments. Finally, first simulations of edge plasma turbulence in X-point geometry are also introduced in a JET geometry. (C) 2016 Elsevier Inc. All rights reserved.
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Davide Galassi, et al.. The TOKAM3X code for edge turbulence fluid simulations of tokamak plasmas in versatile magnetic geometries. Journal of Computational Physics, Elsevier, 2016, 321, pp.606-623. ⟨10.1016/j.jcp.2016.05.038⟩. ⟨hal-01461797⟩
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Yannick Marandet, J. Bucalossi, et al.. Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D-EIRENE. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.555-562. ⟨10.1002/ctpp.201610033⟩. ⟨hal-01455239⟩ Plus de détails...
Cross-field transport in edge tokamak plasmas is known to be dominated by turbulent transport. A dedicated effort has been made to simulate this turbulent transport from first principle models but the numerical cost to run these simulations on the ITER scale remains prohibitive. Edge plasma transport study relies mostly nowadays on so-called transport codes where the turbulent transport is taken into account using effective ad-hoc diffusion coeffecients. In this contribution, we propose to introduce a transport equation for the turbulence intensity in SOLEDGE2D-EIRENE to describe the interchange turbulence properties. Going beyond the empirical diffusive model, this system automatically generates profiles for the turbulent transport and hence reduces the number of degrees of freedom for edge plasma transport codes. We draw inspiration from the k-epsilon model widely used in the neutral fluid community. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Yannick Marandet, J. Bucalossi, et al.. Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D-EIRENE. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.555-562. ⟨10.1002/ctpp.201610033⟩. ⟨hal-01455239⟩
R. Futtersack, C. Colin, Patrick Tamain, Guido Ciraolo, Philippe Ghendrih, et al.. First Principle Modelling of Interplay between Langmuir Probes and Plasma Turbulence. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.575-580. ⟨10.1002/ctpp.201610038⟩. ⟨hal-01455240⟩ Plus de détails...
The interplay between Langmuir probes (LP) and Scrape-Off-Layer plasma turbulence is numerically investigated with the TOKAM2D and TOKAM3X fluid codes. The LP is modelled by biasing a part of the target plates surface; we then study its impact on the turbulent transport 1) in presence of electron temperature fluctuations and 2) with a complete description of the parallel dynamics. We find that a biased probe can disturb local plasma parameters as well as turbulent transport in its vicinity, by polarizing the connected flux tube and thus driving a strong ExB vortex. Moreover, electron temperature fluctuations are found to account significantly those of floating potential, but with a limited impact on flux measurements depending on the probe's exact geometry. The 3D study of the problem shows the attenuation, but the persistency, of these perturbations induced by the presence of the LP. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
R. Futtersack, C. Colin, Patrick Tamain, Guido Ciraolo, Philippe Ghendrih, et al.. First Principle Modelling of Interplay between Langmuir Probes and Plasma Turbulence. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.575-580. ⟨10.1002/ctpp.201610038⟩. ⟨hal-01455240⟩
Patrick Tamain, Hugo Bufferand, L. Carbajal, Yannick Marandet, C. Baudoin, et al.. Interplay between Plasma Turbulence and Particle Injection in 3D Global Simulations. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.569-574. ⟨10.1002/ctpp.201610063⟩. ⟨hal-01455242⟩ Plus de détails...
The impact of a 3D localized particle source on the edge plasma in 3D global turbulence simulations is investigated using the TOKAM3X fluid code. Results apply to advanced fueling methods such as Supersonic Molecular Beam Injection (SMBI) or pellets injection. The fueling source is imposed as a volumetric particle source in the simulations so that the physics leading to the ionization of particles and its localization are not taken into account. As already observed in experiments, the localized particle source strongly perturbs both turbulence and the large scale organization of the edge plasma. The localized increase of the pressure generated by the source drives sonic parallel flows in the plasma, leading to a poloidal redistribution of the particles on the time scale of the source duration. However, the particle deposition also drives localized transverse pressure gradients which impacts the stability of the plasma with respect to interchange processes. The resulting radial transport occurs on a sufficiently fast time scale to compete with the parallel redistribution of particles, leading to immediate radial losses of a significant proportion of the injected particles. Low Field Side (LFS) and High Field Side (HFS) injections exhibit different dynamics due to their interaction with curvature. In particular, HFS particle deposition drives an inward flux leading to differences in the particle deposition efficiency (higher for HFS than LFS). These results demonstrate the importance of taking into account plasma transport in a self-consistent manner when investigating fueling methods. ((c) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Patrick Tamain, Hugo Bufferand, L. Carbajal, Yannick Marandet, C. Baudoin, et al.. Interplay between Plasma Turbulence and Particle Injection in 3D Global Simulations. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.569-574. ⟨10.1002/ctpp.201610063⟩. ⟨hal-01455242⟩
Yannick Marandet, Hugo Bufferand, G. Ciraolo, P. Genesio, P. Meliga, et al.. Effect of Statistical Noise on Simulation Results with a Plasma Fluid Code Coupled to a Monte Carlo Kinetic Neutral Code. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.604-609. ⟨10.1002/ctpp.201610009⟩. ⟨hal-01455237⟩ Plus de détails...
Power exhaust is one of the major challenges that future devices such as ITER and DEMO will face. Because of the lack of identified scaling parameters, predictions for divertor plasma conditions in these devices have to rely on detailed modelling. Most plasma edge simulations carried out so far rely on transport codes, which most of the times consist of a fluid code for the plasma coupled to a kinetic Monte Carlo (MC) code for neutral particles. One of the main difficulties in interpreting code results is the statistical noise from the MC procedure, which makes it difficult to define a convergence criterion for the simulations. In this work, we elaborate on similarities between noisy transport code simulations and turbulence simulations, and argue that the time averaged solution is a well defined stationary solution for the system. We illustrate these ideas with a simple slab test case with fluid neutrals, to which we add synthetic noise. In this case, the effects of noise are found to be significant only at high noise levels and for large enough correlations times.
Yannick Marandet, Hugo Bufferand, G. Ciraolo, P. Genesio, P. Meliga, et al.. Effect of Statistical Noise on Simulation Results with a Plasma Fluid Code Coupled to a Monte Carlo Kinetic Neutral Code. Contributions to Plasma Physics, Wiley-VCH Verlag, 2016, 56 (6-8), pp.604-609. ⟨10.1002/ctpp.201610009⟩. ⟨hal-01455237⟩
Fabio Riva, Clothilde Colin, Julien Denis, Luke Easy, Ivo Furno, et al.. Blob dynamics in the TORPEX experiment: a multi-code validation. Plasma Physics and Controlled Fusion, IOP Publishing, 2016, 58 (4), ⟨10.1088/0741-3335/58/4/044005⟩. ⟨hal-01461784⟩ Plus de détails...
Three-dimensional and two-dimensional seeded blob simulations are performed with five different fluid models, all based on the drift-reduced Braginskii equations, and the numerical results are compared among themselves and validated against experimental measurements provided by the TORPEX device ( Fasoli et al 2006 Phys. Plasmas 13 055902). The five models are implemented in four simulation codes, typically used to simulate the plasma dynamics in the tokamak scrape-off layer, namely BOUT++ (Dudson et al 2009 Comput. Phys. Commun. 180 1467), GBS (Ricci et al 2012 Plasma Phys. Control. Fusion 54 124047), HESEL (Nielsen et al 2015 Phys. Lett. A 379 3097), and TOKAM3X (Tamain et al 2014 Contrib. Plasma Phys. 54 555). Three blobs with different velocities and different stability properties are simulated. The differences observed among the simulation results and the different levels of agreement with experimental measurements are investigated, increasing our confidence in our simulation tools and shedding light on the blob dynamics. The comparisons demonstrate that the radial blob dynamics observed in the three-dimensional simulations is in good agreement with experimental measurements and that, in the present experimental scenario, the two-dimensional model derived under the assumption of k(vertical bar vertical bar) = 0 is able to recover the blob dynamics observed in the three-dimensional simulations. Moreover, it is found that an accurate measurement of the blob temperature is important to perform reliable seeded blob simulations.
Fabio Riva, Clothilde Colin, Julien Denis, Luke Easy, Ivo Furno, et al.. Blob dynamics in the TORPEX experiment: a multi-code validation. Plasma Physics and Controlled Fusion, IOP Publishing, 2016, 58 (4), ⟨10.1088/0741-3335/58/4/044005⟩. ⟨hal-01461784⟩
J. Gounley, G. Boedec, Marc Jaeger, M. Leonetti. Influence of surface viscosity on droplets in shear flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2016, 791, pp.464- 494. ⟨10.1017/jfm.2016.39⟩. ⟨hal-01281643⟩ Plus de détails...
The behaviour of a single droplet in an immiscible external fluid, submitted to shear flow is investigated using numerical simulations. The surface of the droplet is modelled by a Boussinesq–Scriven constitutive law involving the interfacial viscosities and a constant surface tension. A numerical method using Loop subdivision surfaces to represent droplet interface is introduced. This method couples boundary element method for fluid flows and finite element method to take into account the stresses due to the surface dilational and shear viscosities and surface tension. Validation of the numerical scheme with respect to previous analytic and computational work is provided, with particular attention to the viscosity contrast and the shear and dilational viscosities characterized both by a Boussinesq number Bq. Then, influence of equal surface viscosities on steady-state characteristics of a droplet in shear flow are studied, considering both small and large deformations and for a large range of bulk viscosity contrast. We find that small deformation analysis is surprisingly predictive at moderate and high surface viscosities. Equal surface viscosities decrease the Taylor deformation parameter and tank-treading angle and also strongly modify the dynamics of the droplet: when the Boussinesq number (surface viscosity) is large relative to the capillary number (surface tension), the droplet displays damped oscillations prior to steady-state tank-treading, reminiscent from the behaviour at large viscosity contrast. In the limit of infinite capillary number Ca, such oscillations are permanent. The influence of surface viscosities on breakup is also investigated, and results show that the critical capillary number is increased. A diagram (Bq;Ca) of breakup is established with the same inner and outer bulk viscosities. Additionally, the separate roles of shear and dilational surface viscosity are also elucidated, extending results from small deformation analysis. Indeed, shear (dilational) surface viscosity increases (decreases) the stability of drops to breakup under shear flow. The steady-state deformation (Taylor parameter) varies nonlinearly with each Boussinesq number or a linear combination of both Boussinesq numbers. Finally, the study shows that for certain combinations of shear and dilational viscosities, drop deformation for a given capillary number is the same as in the case of a clean surface while the inclination angle varies.
J. Gounley, G. Boedec, Marc Jaeger, M. Leonetti. Influence of surface viscosity on droplets in shear flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2016, 791, pp.464- 494. ⟨10.1017/jfm.2016.39⟩. ⟨hal-01281643⟩
J. Denis, B. Pégourié, J. Bucalossi, Hugo Bufferand, Guido Ciraolo, et al.. Wall surface temperature calculation in the SolEdge2D-EIRENE transport code. Physica Scripta, IOP Publishing, 2016, 15th International Conference on Plasma-Facing Materials and Components for Fusion Applications, T167, ⟨10.1088/0031-8949/T167/1/014073⟩. ⟨hal-01459103⟩ Plus de détails...
A thermal wall model is developed for the SolEdge2D-EIRENE edge transport code for calculating the surface temperature of the actively-cooled vessel components in interaction with the plasma. This is a first step towards a self-consistent evaluation of the recycling of particles, which depends on the wall surface temperature. The proposed thermal model is built to match both steady-state temperature and time constant of actively-cooled plasma facing components. A benchmark between this model and the Finite Element Modelling code CAST3M is performed in the case of an ITER-like monoblock. An example of application is presented for a SolEdge2D-EIRENE simulation of a medium-power discharge in the WEST tokamak, showing the steady-state wall temperature distribution and the temperature cycling due to an imposed Edge Localised Mode-like event.
J. Denis, B. Pégourié, J. Bucalossi, Hugo Bufferand, Guido Ciraolo, et al.. Wall surface temperature calculation in the SolEdge2D-EIRENE transport code. Physica Scripta, IOP Publishing, 2016, 15th International Conference on Plasma-Facing Materials and Components for Fusion Applications, T167, ⟨10.1088/0031-8949/T167/1/014073⟩. ⟨hal-01459103⟩
Achim Guckenberger, Marcel P. Schrame, Paul G. Chen, Marc Leonetti, Stephan Gekle. On the bending algorithms for soft objects in flows. Computer Physics Communications, Elsevier, 2016, 207, pp.1-23. ⟨10.1016/j.cpc.2016.04.018⟩. ⟨hal-01314722⟩ Plus de détails...
One of the most challenging aspects in the accurate simulation of three-dimensional soft objects such as vesicles or biological cells is the computation of membrane bending forces. The origin of this difficulty stems from the need to numerically evaluate a fourth order derivative on the discretized surface geometry. Here we investigate six different algorithms to compute membrane bending forces, including regularly used methods as well as novel ones. All are based on the same physical model (due to Canham and Helfrich) and start from a surface discretization with flat triangles. At the same time, they differ substantially in their numerical approach. We start by comparing the numerically obtained mean curvature, the Laplace-Beltrami operator of the mean curvature and finally the surface force density to analytical results for the discocyte resting shape of a red blood cell. We find that none of the considered algorithms converges to zero error at all nodes and that for some algorithms the error even diverges. There is furthermore a pronounced influence of the mesh structure: Discretizations with more irregular triangles and node connectivity present serious difficulties for most investigated methods. To assess the behavior of the algorithms in a realistic physical application, we investigate the deformation of an initially spherical capsule in a linear shear flow at small Reynolds numbers. To exclude any influence of the flow solver, two conceptually very different solvers are employed: the Lattice-Boltzmann and the Boundary Integral Method. Despite the largely different quality of the bending algorithms when applied to the static red blood cell, we find that in the actual flow situation most algorithms give consistent results for both hydrodynamic solvers. Even so, a short review of earlier works reveals a wide scattering of reported results for, e.g., the Taylor deformation parameter. Besides the presented application to biofluidic systems, the investigated algorithms are also of high relevance to the computer graphics and numerical mathematics communities.
Achim Guckenberger, Marcel P. Schrame, Paul G. Chen, Marc Leonetti, Stephan Gekle. On the bending algorithms for soft objects in flows. Computer Physics Communications, Elsevier, 2016, 207, pp.1-23. ⟨10.1016/j.cpc.2016.04.018⟩. ⟨hal-01314722⟩
Abir Bouledjouidja, Yasmine Masmoudi, Michelle Sergent, Vivek Trivedi, Abdeslam-Hassen Meniai, et al.. Drug loading of foldable commercial intraocular lenses using supercritical impregnation
. International Journal of Pharmaceutics, Elsevier, 2016, 500, pp.85 - 99. ⟨hal-01266557⟩ Plus de détails...
The drug delivery through intraocular lenses (IOLs) allows the combination of cataract surgery act and postoperative treatment in a single procedure. In order to prepare such systems, “clean” supercritical CO2 processes are studied for loading commercial IOLs with ophthalmic drugs. Ciprofloxacin (CIP, an antibiotic) and dexamethasone 21-phosphate disodium (DXP, an anti-inflammatory drug) were impregnated into foldable IOLs made from poly-2-hydroxyethyl methacrylate (P-HEMA). A first pre-treatment step was conducted in order to remove absorbed conditioning physiological solution. Supercritical impregnations were then performed by varying the experimental conditions. In order to obtain transparent IOLs and avoid the appearance of undesirable foaming, it was necessary to couple slow pressurization and depressurization phases during supercritical treatments. The impregnation yields were determined through drug release studies. For both drugs, release studies showdeep and reproducible impregnation for different diopters. For the system P-HEMA/CIP, a series of impregnations was performed to delimit the experimental range at two pressures (80 and 200 bar) in the presence or absence of ethanol as a co-solvent for two diopters (+5.0 D and +21.0 D). Increase in pressure in the absence of a co-solvent resulted in improved CIP impregnation. The addition of ethanol (5 mol%) produced impregnation yields comparable to those obtained at 200 bar without co-solvent. A response surface methodology based on experimental designs was used to study the influence of operating conditions on impregnation of IOLs (+21.0 D) in the absence of co-solvent. Two input variables with 5 levels each were considered; the pressure (80–200 bar) and the impregnation duration (30–240 min). CIP impregnation yields ranging between 0.92 and 3.83 μgCIP/mgIOL were obtained from these experiments and response surface indicated the pressure as a key factor in the process. The DXP impregnation in P-HEMA was higher than CIP at all the tested conditions (8.50–14.53 μgDXP/mgIOL). Furthermore, unlike CIP, highest DXP impregnation yields were obtained in the presence of ethanol as a co-solvent (5 mol%). NMR spectroscopy was performed to confirm complete removal of ethanol in the co-solvent-treated IOLs
Abir Bouledjouidja, Yasmine Masmoudi, Michelle Sergent, Vivek Trivedi, Abdeslam-Hassen Meniai, et al.. Drug loading of foldable commercial intraocular lenses using supercritical impregnation
. International Journal of Pharmaceutics, Elsevier, 2016, 500, pp.85 - 99. ⟨hal-01266557⟩
Lyes Bordja, Emilia Arco, Éric Serre, Rachid Bessaih. EFFECTS OF AXIAL MAGNETIC FIELD AND THERMAL CONVECTION ON A COUNTERROTATING VON KARMAN FLOW. Heat Transfer Research, Begell House, 2016, 47 (5), pp.471-488. ⟨10.1615/HeatTransRes.2016007441⟩. ⟨hal-01462070⟩ Plus de détails...
The effects of thermal convection and of a constant axial magnetic field on a von Karman flow driven by the exact counter-rotation of two lids are investigated in a vertical cylinder of aspect ratio Gamma(= height/radius) = 2 at a fixed Reynolds number Re(= Omega R-2/v) = 300. Direct numerical simulations are performed when varying separately the Rayleigh and Hartmann numbers in the range [0, 1800] and [0, 20], respectively, in the limit of the Boussinesq approximation and of a small magnetic Reynolds numbers, Re-m << 1. Without a magnetic field, the base flow symmetries of the von Karman flow are broken by thermal convection that becomes dominant in the range of Ra [500, 1000]. Three-dimensional solutions are characterized by the occurrence of a steady, m = 1, azimuthal mode exhibiting a cat's eye vortex in the circumferential plane. When increasing the Rayleigh number in the range [500, 1000], the vortex pulsates in an oscillatory manner, due to variations of the flow intensity. Otherwise, increasing the axial magnetic field intensity stabilizes the flow, and the oscillatory motion can be inhibited. Numerical solutions show that the critical Rayleigh number for transition increases linearly with the Hartmann number. Finally, results show that when varying the Rayleigh number, the structure of the electric potential can be strongly modified by thermal convection. Such an observation suggests new induction mechanisms in the case of small nonzero values of the magnetic Reynolds number.
Lyes Bordja, Emilia Arco, Éric Serre, Rachid Bessaih. EFFECTS OF AXIAL MAGNETIC FIELD AND THERMAL CONVECTION ON A COUNTERROTATING VON KARMAN FLOW. Heat Transfer Research, Begell House, 2016, 47 (5), pp.471-488. ⟨10.1615/HeatTransRes.2016007441⟩. ⟨hal-01462070⟩
R. Trozzo, G. Boedec, M. Leonetti, M. Jaeger. Axisymmetric Boundary Element Method for vesicles in a capillary. Journal of Computational Physics, Elsevier, 2015, 289, pp.62-82. ⟨10.1016/j.jcp.2015.02.022⟩. ⟨hal-01281961⟩ Plus de détails...
The problem of a vesicle transported by a fluid flow can present a large range of length scales. One example is the case of a vesicle producing a tether, and eventually pearls, in an elongational flow. Another case occurs when a lubrication film is formed, such as during the short range interaction between two vesicles. Such problems are still challenging for 3D simulations. On the other hand, a good understanding could be obtained by first considering the axisymmetric regime when such a regime exists. An axisymmetric model could then be used, without the criticisms that can be made of a 2D approach. We propose such a model, primarily interested in flows through narrow cylindrical capillaries. Two options are compared, with and without explicit representation of the capillary boundaries by a mesh. The numerical effort is characterized as a function of the vesicle’s initial shape, the flow magnitude and the confinement. The model is able to treat typical configurations of red blood cells flowing through very narrow pores with extremely thin lubrication films.
R. Trozzo, G. Boedec, M. Leonetti, M. Jaeger. Axisymmetric Boundary Element Method for vesicles in a capillary. Journal of Computational Physics, Elsevier, 2015, 289, pp.62-82. ⟨10.1016/j.jcp.2015.02.022⟩. ⟨hal-01281961⟩
Patrick Tamain, Philippe Ghendrih, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, et al.. Multi-scale self-organisation of edge plasma turbulent transport in 3D global simulations. Plasma Physics and Controlled Fusion, IOP Publishing, 2015, 57 (5), pp.054014. ⟨10.1088/0741-3335/57/5/054014⟩. ⟨hal-01299732⟩ Plus de détails...
The 3D global edge turbulence code TOKAM3X is used to study the properties of edge particle turbulent transport in circular limited plasmas, including both closed and open flux surfaces. Turbulence is driven by an incoming particle flux from the core plasma and no scale separation between the equilibrium and the fluctuations is assumed. Simulations show the existence of a complex self-organization of turbulence transport coupling scales ranging from a few Larmor radii up to the machine scale. Particle transport is largely dominated by small scale turbulence with fluctuations forming quasi field-aligned filaments. Radial particle transport is intermittent and associated with the propagation of coherent structures on long distances via avalanches. Long range correlations are also found in the poloidal and toroidal direction. The statistical properties of fluctuations vary with the radial and poloidal directions, with larger fluctuation levels and intermittency found in the outboard scrape-off layer (SOL). Radial turbulent transport is strongly ballooned, with 90% of the flux at the separatrix flowing through the low-field side. One of the main consequences is the existence of quasi-sonic asymmetric parallel flows driving a net rotation of the plasma. Simulations also show the spontaneous onset of an intermittent E × B rotation characterized by a larger shear at the separatrix. Strong correlation is found between the turbulent particle flux and the E × B flow shear in a phenomenology reminiscent of H-mode physics. The poloidal position of the limiter is a key player in the observed dynamics.
Patrick Tamain, Philippe Ghendrih, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, et al.. Multi-scale self-organisation of edge plasma turbulent transport in 3D global simulations. Plasma Physics and Controlled Fusion, IOP Publishing, 2015, 57 (5), pp.054014. ⟨10.1088/0741-3335/57/5/054014⟩. ⟨hal-01299732⟩
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, P. Genesio, et al.. Comparison on heat flux deposition between carbon and tungsten wall – Investigations on energy recycling. Journal of Nuclear Materials, Elsevier, 2015, 463, pp.420-423. ⟨10.1016/j.jnucmat.2014.09.061⟩. ⟨hal-01225205⟩ Plus de détails...
The influence of the plasma facing components material on the scrape-off layer plasma is investigated. In particular, the energy recycling is found to be more pronounced for tungsten wall compared with carbon wall. Edge plasma simulations performed with the transport code SOLEDGE2D-EIRENE show that this enhanced energy recycling in the tungsten case leads to an increase of the scrape-off layer temperature. Moreover, the energy recycling depends on the ion angle of incidence with the wall. A PIC code has been used to model the ion acceleration in the magnetic pre-sheath and determine the later angle of incidence. These simulations show that ions mostly impact the wall with rather shallow incident angles leading to a further increase of the energy recycling.
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, P. Genesio, et al.. Comparison on heat flux deposition between carbon and tungsten wall – Investigations on energy recycling. Journal of Nuclear Materials, Elsevier, 2015, 463, pp.420-423. ⟨10.1016/j.jnucmat.2014.09.061⟩. ⟨hal-01225205⟩
Hugo Bufferand, Guido Ciraolo, Yannick Marandet, Jérome Bucalossi, Philippe Ghendrih, et al.. Numerical modelling for divertor design of the WEST device with a focus on plasma–wall interactions. Nuclear Fusion, IOP Publishing, 2015, 55 (5), pp.053025. ⟨hal-01225195⟩ Plus de détails...
In the perspective of operating tungsten monoblocks in WEST, the ongoing major upgrade of the Tore Supra tokamak, a dedicated modelling effort has been carried out to simulate the interaction between the edge plasma and the tungsten wall. A new transport code, SolEdge2D–EIRENE, has been developed with the ability to simulate the plasma up to the first wall. This is especially important for steady state operation, where thermal loads on all the plasma facing components, even remote from the plasma, are of interest. Moreover, main chamber tungsten sources are thought to dominate the contamination of the plasma core. We present here in particular new developments aimed at improving the description of the interface between the plasma and the wall, namely a way to treat sheath physics in a more faithful way using the output of 1D particle in cell simulations. Moreover, different models for prompt redeposition have been implemented and are compared. The latter is shown to play an important role in the balance between divertor and main chamber sources.
Hugo Bufferand, Guido Ciraolo, Yannick Marandet, Jérome Bucalossi, Philippe Ghendrih, et al.. Numerical modelling for divertor design of the WEST device with a focus on plasma–wall interactions. Nuclear Fusion, IOP Publishing, 2015, 55 (5), pp.053025. ⟨hal-01225195⟩
Richard Howard, Eric Serre. Large-eddy simulation in a mixing tee junction: High-order turbulent
statistics analysis. International Journal of Heat and Fluid Flow, Elsevier, 2015, 51, pp.65-77. ⟨hal-01138803⟩ Plus de détails...
This study analyses the mixing and thermal fluctuations induced in a mixing tee junction with circular cross-sections when cold water flowing in a pipe is joined by hot water from a branch pipe. This config- uration is representative of industrial piping systems in which temperature fluctuations in the fluid may cause thermal fatigue damage on the walls. Implicit large-eddy simulations (LES) are performed for equal inflow rates corresponding to a bulk Reynolds number Re= 39,080. Two different thermal boundary conditions are studied for the pipe walls; an insulating adiabatic boundary and a conducting steel wall boundary. The predicted flow structures show a satisfactory agreement with the literature. The velocity and thermal fields (including high-order statistics) are not affected by the heat transfer with the steel walls. However, predicted thermal fluctuations at the boundary are not the same between the flow and the solid, showing that solid thermal fluctuations cannot be predicted by the knowledge of the fluid thermal fluctuations alone. The analysis of high-order turbulent statistics provides a better understand- ing of the turbulence features. In particular, the budgets of the turbulent kinetic energy and temperature variance allows a comparative analysis of dissipation, production and transport terms. It is found that the turbulent transport term is an important term that acts to balance the production. We therefore use a priori tests to evaluate three different models for the triple correlation
Richard Howard, Eric Serre. Large-eddy simulation in a mixing tee junction: High-order turbulent
statistics analysis. International Journal of Heat and Fluid Flow, Elsevier, 2015, 51, pp.65-77. ⟨hal-01138803⟩
Journal: International Journal of Heat and Fluid Flow
R. Leybros, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Investigation of drift velocity effects on the EDGE and SOL transport. Journal of Nuclear Materials, Elsevier, 2015, 463, pp.489-492. ⟨10.1016/j.jnucmat.2014.10.079⟩. ⟨hal-01225211⟩ Plus de détails...
To understand the mechanisms behind poloidal asymmetries of the transport in the edge and SOL plasma, it is important to take into account drift velocity in the transport model. We investigate the effects of an imposed radial electric field on the plasma equilibrium in the transport code SOLEDGE2D. In the edge, we show an important modification of the flow pattern due to poloidal E × B drift velocity. The drift velocity generates asymmetry of the density through the Pfirsch–Schluter flows which creates an important parallel rotation through the viscous balance. In comparison to heat load imbalance studies in the SOL of divertor tokamak, a strong link between the amplitude of the radial electric field and the heat load imbalance in the SOL of limiter tokamak has been highlighted using different amplitude of the imposed radial electric field.
R. Leybros, Hugo Bufferand, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Investigation of drift velocity effects on the EDGE and SOL transport. Journal of Nuclear Materials, Elsevier, 2015, 463, pp.489-492. ⟨10.1016/j.jnucmat.2014.10.079⟩. ⟨hal-01225211⟩
Clothilde Colin, Patrick Tamain, Frederic Schwander, Eric Serre, Hugo Bufferand, et al.. Impact of the plasma-wall contact position on edge turbulent transport and poloidal asymmetries in 3D global turbulence simulations. Journal of Nuclear Materials, Elsevier, 2015, 463, pp.654-658. ⟨10.1016/j.jnucmat.2015.01.019⟩. ⟨hal-01225200⟩ Plus de détails...
A 3D global turbulence fluid code, TOKAM3X is used to investigate the effect of the limiter position on the edge plasma parallel flows and density profiles. Six configurations with different poloidal contact points in the machine are considered. For each one, asymmetric quasi-sonic parallel flows are found, owing to the ballooning of radial turbulent transport around the LFS mid-plane. In spite of the relative simplicity of the model used (isothermal, sheat-limited, no recycling), simulations exhibit trends in-line with experimental findings. Reversal of the flows is found when the limiter is moved from −30° under to 30° above the outboard mid-plane. The SOL width varies with the poloidal location and depends notably on the poloidal position of the limiter. Turbulence itself is shown to be impacted by the position of the limiter, radial transport appearing less ballooned with a LFS limiter than with a HFS.
Clothilde Colin, Patrick Tamain, Frederic Schwander, Eric Serre, Hugo Bufferand, et al.. Impact of the plasma-wall contact position on edge turbulent transport and poloidal asymmetries in 3D global turbulence simulations. Journal of Nuclear Materials, Elsevier, 2015, 463, pp.654-658. ⟨10.1016/j.jnucmat.2015.01.019⟩. ⟨hal-01225200⟩
H Guillard, M Bilanceri, C Colin, Philippe Ghendrih, G Giorgiani, et al.. Parallel Kelvin-Helmholtz instability in edge plasma. Journal of Physics: Conference Series, IOP Publishing, 2014, Joint Varenna-Lausanne International Workshop 2014, 561, pp.012009. ⟨10.1088/1742-6596/561/1/012009⟩. ⟨hal-01100365⟩ Plus de détails...
In the scrape-off layer (SOL) of tokamaks, the flow acceleration due to the presence of limiter or divertor plates rises the plasma velocity in a sonic regime. These high velocities imply the presence of a strong shear between the SOL and the core of the plasma that can possibly trigger some parallel shear flow instability. The existence of these instabilities, denoted as parallel Kelvin-Helmholtz instability in some works [1, 2] have been investigated theoretically in [3] using a minimal model of electrostatic turbulence composed of a mass density and parallel velocity equations. This work showed that the edge plasma around limiters might indeed be unstable to this type of parallel shear flow instabilities. In this work, we perform 3D simulations of the same simple mathematical model to validate an original finite volume numerical method aimed to the numerical study of edge plasma. This method combines the use of triangular unstructured meshes in the poloidal section and structured meshes in the toroidal direction and is particularly suited to the representation of the real complex geometry of the vacuum chamber of a tokamak. The numerical results confirm that in agreement with the theoretical expectations as well as with other numerical methods, the sheared flows in the SOL are subject to parallel Kelvin-Helmholtz instabilities. However, the growth rate of these instabilities is low and these computations require both a sufficient spatial resolution and a long simulation time. This makes the simulation of parallel Kelvin-Helmholtz instabilities a demanding benchmark.
H Guillard, M Bilanceri, C Colin, Philippe Ghendrih, G Giorgiani, et al.. Parallel Kelvin-Helmholtz instability in edge plasma. Journal of Physics: Conference Series, IOP Publishing, 2014, Joint Varenna-Lausanne International Workshop 2014, 561, pp.012009. ⟨10.1088/1742-6596/561/1/012009⟩. ⟨hal-01100365⟩
Denis Martinand, Eric Serre, Richard M. Lueptow. Mechanisms for the transition to waviness for Taylor vortices. Physics of Fluids, American Institute of Physics, 2014, 26 (9), pp.094102. ⟨10.1063/1.4895400⟩. ⟨hal-01300402⟩ Plus de détails...
Building on the weakly nonlinear amplitude equation of the saturated Taylor vortices developing in a Taylor–Couette cell with a rotating inner cylinder and a fixed outer one, the physical mechanism underlying the destabilization of these vortices resulting in azimuthal waviness is addressed using Floquet analysis. For narrow gap configurations, analysis and direct numerical simulations together with existing experimental results support the idea that the waviness is generated by the axial shear in the azimuthal velocity due to the alternate advection by the Taylor vortices of azimuthal momentum between the cylinders. For wide gap configurations, this mechanism is no longer able to drive the azimuthal waviness and a different mechanism tends to select a subharmonic instability.
Denis Martinand, Eric Serre, Richard M. Lueptow. Mechanisms for the transition to waviness for Taylor vortices. Physics of Fluids, American Institute of Physics, 2014, 26 (9), pp.094102. ⟨10.1063/1.4895400⟩. ⟨hal-01300402⟩
Jose Joaquin Sanchez-Alvarez, Eric Serre, Emilia Arco, Friedrich.H Busse. Geometry effects on Rayleigh-Benard convection in rotating annular ă layers. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2014, 89 (6), ⟨10.1103/PhysRevE.89.063013⟩. ⟨hal-01464703⟩ Plus de détails...
Rayleigh-Benard convection is investigated in rotating annular cavities ă at a moderate dimensionless rotation rate Omega = 60. The onset of ă convection is in the form of azimuthal traveling waves that set in at ă the sidewalls and at values of the Rayleigh number significantly below ă the value of the onset of convection in an infinitely extended layer. ă The present study addresses the effects of curvature and confinement on ă the onset of sidewall convection by using three-dimensional spectral ă solutions of the Oberbeck-Boussinesq equations. Such solutions ă demonstrate that the curvature of the outer boundary promotes the onset ă of the wall mode, while the opposite curvature of the inner boundary ă tends to delay the onset of the wall mode. An inner sidewall with a ă radius as low as one tenth of its height is sufficient, however, to ă support the onset of a sidewall mode. When radial confinement is ă increased the two independent traveling waves interact and eventually ă merge to form a nearly steady pattern of convection.
Jose Joaquin Sanchez-Alvarez, Eric Serre, Emilia Arco, Friedrich.H Busse. Geometry effects on Rayleigh-Benard convection in rotating annular ă layers. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2014, 89 (6), ⟨10.1103/PhysRevE.89.063013⟩. ⟨hal-01464703⟩
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Philippe Ghendrih, et al.. 3D properties of edge turbulent transport in full-torus simulations and their impact on poloidal asymmetries. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.555-559. ⟨10.1002/ctpp.201410017⟩. ⟨hal-01053290⟩ Plus de détails...
The 3D fluid turbulence code TOKAM3X is used to investigate the 3D properties of edge turbulent transport and their impact on poloidal asymmetries. Simulations are run in circular limited plasmas in a domain covering both closed and open flux surfaces. Turbulence characteristics exhibit large inhomogeneities both in the radial and poloidal directions reminiscent of experimental observations. The low field side mid-plane in particular is found to be locally more fluctuating and intermittent than the rest of the Scrape-Off-Layer (SOL). As a consequence of this asymmetry, radial turbulent transport, that represents 80 to 90% of the total radial flux, is strongly ballooned, with 75% of the flux flowing through LFS. The equilibrium of the edge plasma is impacted by this asymmetry through the existence of large amplitude asymmetric parallel flows as well as through the development of poloidally asymmetric radial decay lengths making it impossible to define a single SOL width.
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Philippe Ghendrih, et al.. 3D properties of edge turbulent transport in full-torus simulations and their impact on poloidal asymmetries. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.555-559. ⟨10.1002/ctpp.201410017⟩. ⟨hal-01053290⟩
Nils Tilton, Eric Serre, Denis Martinand, Richard M. Lueptow. A 3D pseudospectral algorithm for fluid flows with permeable walls. Application to filtration. Computers and Fluids, Elsevier, 2014, 93, pp.129-145. ⟨10.1016/j.compfluid.2014.01.003⟩. ⟨hal-01053339⟩ Plus de détails...
The present work proposes a Chebyshev-collocation Fourier-Galerkin pseudospectral method for simulating unsteady, three-dimensional, fluid flows in cylindrical geometries with pressure-driven flow through permeable boundaries. Such systems occur in diverse applications and are challenging to simulate due to an additional velocity-pressure coupling on the permeable walls through Darcy's law. The present work extends the projection method of Raspo et al. (2002) to assure Darcy's law is satisfied exactly. A multidomain solver allows the efficient treatment of open boundary conditions that necessitate permeability buffers and a sponge layer. The method is spectrally convergent, and we demonstrate that pressure-prediction is necessary to obtain second-order temporal accuracy. The ability of the method to simulate complicated physical systems is demonstrated by simulating subcritical and supercritical flows in rotating filtration in Taylor-Couette cells. For subcritical cases, numerical results show excellent agreement with analytical solutions. For supercritical cases, the numerical method accurately resolves convectively and absolutely unstable flows with traveling toroidal and helical vortical structures that are in good agreement with a local linear stability analysis and experimental observations.
Nils Tilton, Eric Serre, Denis Martinand, Richard M. Lueptow. A 3D pseudospectral algorithm for fluid flows with permeable walls. Application to filtration. Computers and Fluids, Elsevier, 2014, 93, pp.129-145. ⟨10.1016/j.compfluid.2014.01.003⟩. ⟨hal-01053339⟩
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich Busse. Geometry effects on the onset of rotating Rayleigh-Bénard convection in annuli. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2014, 89, pp.063013. ⟨hal-01087216⟩ Plus de détails...
Rayleigh-Bénard convection is investigated in rotating annular cavities at a moderate rotationrate (square root of the Taylor number) Omega= 60. The onset of convection is in the form of azimuthaltraveling waves that set in at the sidewalls and at values of the Rayleigh number significantly belowthe value of the onset of convection in an infinitely extended layer. When curvature effect becomessignificant, the waves traveling along the sidewalls have different critical Rayleigh numbers and com-plex Guinzburg-Landau equations are no longer applicable. The present study addresses the effectsof curvature and confinement on the onset of sidewall convection by using three-dimensional spectralsolutions of the Oberbeck-Boussinesq equations. Such solutions demonstrate that the curvature ofthe outer boundary promotes the onset of the wall mode, while the opposite curvature of the innerboundary tends to delay the onset of the wall mode. When radial confinement is increased the twoindependent traveling waves can interact and eventually merge to form a nearly steady pattern ofconvection.
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich Busse. Geometry effects on the onset of rotating Rayleigh-Bénard convection in annuli. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2014, 89, pp.063013. ⟨hal-01087216⟩
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Density regimes and heat flux deposition in the WEST shallow divertor configuration. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.378-382. ⟨10.1002/ctpp.201410026⟩. ⟨hal-01053281⟩ Plus de détails...
To support ITER divertor design, the WEST project on Tore Supra aims at studying high heat fluxes on tungsten monoblock during long pulses. In that persective, a particular attention is paid to simulate the edge plasma interaction with complex PFCs using the transport code SOLEDGE2D-EIRENE. The plasma response to a heating and puffing scenario is described as well as the so-called divertor density regimes, characterizing the operational domain of the WEST divertor. These results are compared for two different magnetic configurations: a semi-open double null divertor with the X-point away from the target plates and a shallow divertor configuration with the X-point close to the targets.
Hugo Bufferand, Jérome Bucalossi, Guido Ciraolo, Nicolas Fedorczak, Philippe Ghendrih, et al.. Density regimes and heat flux deposition in the WEST shallow divertor configuration. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.378-382. ⟨10.1002/ctpp.201410026⟩. ⟨hal-01053281⟩
Alejandro Paredes, Hugo Bufferand, Guido Ciraolo, Frédéric Schwander, Eric Serre, et al.. A penalization technique to model plasma facing components in a tokamak with temperature variations. Journal of Computational Physics, Elsevier, 2014, 274, pp.283-298. ⟨hal-01087225⟩ Plus de détails...
To properly address turbulent transport in the edge plasma region of a tokamak, it is mandatory to describe the particle and heat outflow on wall components, using an accurate representation of the wall geometry. This is challenging for many plasma transport codes, which use a structured mesh with one coordinate aligned with magnetic surfaces. We propose here a penalization technique that allows modelingof particle and heat transport using such structured mesh, while also accounting for geometrically complex plasma-facing components. Solid obstacles are considered as particle and momentum sinks whereas ionic and electronic temperature gradients are imposed on both sides of the obstacles along the magnetic field direction using delta functions (Dirac). Solutions exhibit plasma velocities (M=1) and temperatures fluxes at the plasma–wall boundaries that match with boundary conditions usually implemented in fluid codes. Grid convergence and error estimates are found to be in agreement with theoretical results obtained for neutral fluid conservation equations. The capability of the penalization technique is illustrated by introducing the non-collisional plasma region expected by the kinetic theory in the immediate vicinity of the interface, that is impossible when considering fluid boundary conditions. Axisymmetric numerical simulations show the efficiency of the method to investigate the large-scale transport at the plasma edge including the separatrix and in realistic complex geometries while keeping a simple structured grid.
Alejandro Paredes, Hugo Bufferand, Guido Ciraolo, Frédéric Schwander, Eric Serre, et al.. A penalization technique to model plasma facing components in a tokamak with temperature variations. Journal of Computational Physics, Elsevier, 2014, 274, pp.283-298. ⟨hal-01087225⟩
Guillaume Fontaine, Sébastien Poncet, Eric Serre. Multidomain Extension of a Pseudospectral Algorithm for the Direct Simulation of Wall-Confined Rotating Flows. M. Azaiez, H. El Fekih, J.S. Hesthaven. Lecture Notes in Computational Science and Engineering, 95, Springer, pp.261 - 271, 2014, ⟨10.1007/978-3-319-01601-6_21⟩. ⟨hal-01098589⟩ Plus de détails...
In this work, we improve an existing pseudospectral algorithm, in order to extend its properties to a multidomain patching of a rotating cavity. Viscous rotating flows have been widely studied over the last decades, either on industrial or aca-demic approaches. Nevertheless, the range of Reynolds numbers reached in indus-trial devices implies very high resolutions of the spatial problem, which are clearly unreachable using a monodomain approach. Hence, we worked on the multido-main extension of the existing divergence-free Navier-Stokes solver with a Schur approach. The particularity of such an approach is that it does not require any sub-domain superposition: the value of a variable on the boundary between two adjacent subdomains is treated as a boundary condition of a local Helmholtz solver. This value is computed on a direct way via a so-called continuity influence matrix and the derivative jump of an homogeneous solution computed independently on each subdomain. Such a method is known to have both good scalability and accuracy. It has been validated on two well documented three-dimensional rotating flows.
Guillaume Fontaine, Sébastien Poncet, Eric Serre. Multidomain Extension of a Pseudospectral Algorithm for the Direct Simulation of Wall-Confined Rotating Flows. M. Azaiez, H. El Fekih, J.S. Hesthaven. Lecture Notes in Computational Science and Engineering, 95, Springer, pp.261 - 271, 2014, ⟨10.1007/978-3-319-01601-6_21⟩. ⟨hal-01098589⟩
Hugo Bufferand, Guido Ciraolo, Guilhem Dif-Pradalier, Philippe Ghendrih, Patrick Tamain, et al.. Magnetic geometry and particle source drive of supersonic divertor regimes. Plasma Physics and Controlled Fusion, IOP Publishing, 2014, 56 (122001), ⟨10.1088/0741-3335/56/12/122001⟩. ⟨hal-01225185⟩ Plus de détails...
We present a comprehensive picture of the mechanisms driving the transition from subsonic to supersonic flows in tokamak plasmas. We demonstrate that supersonic parallel flows into the divertor volume are ubiquitous at low density and governed by the divertor magnetic geometry. As the density is increased, subsonic divertor plasmas are recovered. On detachment, we show the change in particle source can also drive the transition to a supersonic regime. The comprehensive theoretical analysis is completed by simulations in ITER geometry. Such results are essential in assessing the divertor performance and when interpreting measurements and experimental evidence. The generation of large-scale flows in laboratory plasma is a highly non-linear problem. In a standard fashion it is considered that the flows remain subsonic away from the wall, the occurrence of supersonic flows being singular. We show here that the geometrical features of key configurations for fusion plasma can lead to supersonic flows.
Hugo Bufferand, Guido Ciraolo, Guilhem Dif-Pradalier, Philippe Ghendrih, Patrick Tamain, et al.. Magnetic geometry and particle source drive of supersonic divertor regimes. Plasma Physics and Controlled Fusion, IOP Publishing, 2014, 56 (122001), ⟨10.1088/0741-3335/56/12/122001⟩. ⟨hal-01225185⟩