Plasmas de tokamak: Modélisation, transport turbulent, plasma de bord
Méthodes numériques d'ordre élevé
Publications scientifiques au M2P2
2017
E. Constant, J. Favier, M. Meldi, P. Meliga, E. Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers & Fluids, 2017, 157, pp.55 - 72. 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.
E. Constant, J. Favier, M. Meldi, P. Meliga, E. Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers & Fluids, 2017, 157, pp.55 - 72. <10.1016/j.compfluid.2017.08.001>. <hal-01591562>
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. 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. 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>
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), . 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. 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, T167, . 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, T167, <10.1088/0031-8949/T167/1/014073>. <hal-01459103>
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. 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>
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. 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. 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>
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. 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. 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>
Richard Howard, Eric Serre. Large-eddy simulation in a mixing tee junction: High-order turbulentstatistics analysis. International Journal of Heat and Fluid Flow, Elsevier, 2015, 51, pp.65-77. 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 turbulentstatistics analysis. International Journal of Heat and Fluid Flow, Elsevier, 2015, 51, pp.65-77. <hal-01138803>
Journal: International Journal of Heat and Fluid Flow
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. 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>
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. 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>
Alejandro Paredes, Hugo Bufferand, Guido Ciraolo, Frédéric Schwander, Eric Serre, et al.. A penalization technique to model plasma facing components in a tokamak ă with temperature variations. Journal of Computational Physics, Elsevier, 2014, 274, pp.283-298. Plus de détails...
To properly address turbulent transport in the edge plasma region of a ă tokamak, it is mandatory to describe the particle and heat outflow on ă wall components, using an accurate representation of the wall geometry. ă This is challenging for many plasma transport codes, which use a ă structured mesh with one coordinate aligned with magnetic surfaces. We ă propose here a penalization technique that allows modeling of particle ă and heat transport using such structured mesh, while also accounting for ă geometrically complex plasma-facing components. Solid obstacles are ă considered as particle and momentum sinks whereas ionic and electronic ă temperature gradients are imposed on both sides of the obstacles along ă the magnetic field direction using delta functions (Dirac). Solutions ă exhibit plasma velocities (M = 1) and temperatures fluxes at the ă plasma-wall boundaries that match with boundary conditions usually ă implemented in fluid codes. Grid convergence and error estimates are ă found to be in agreement with theoretical results obtained for neutral ă fluid conservation equations. The capability of the penalization ă technique is illustrated by introducing the non-collisional plasma ă region expected by the kinetic theory in the immediate vicinity of the ă interface, that is impossible when considering fluid boundary ă conditions. Axisymmetric numerical simulations show the efficiency of ă the method to investigate the large-scale transport at the plasma edge ă including the separatrix and in realistic complex geometries while ă keeping a simple structured grid. (C) 2014 Elsevier Inc. All rights ă reserved.
Alejandro Paredes, Hugo Bufferand, Guido Ciraolo, Frédéric Schwander, Eric Serre, et al.. A penalization technique to model plasma facing components in a tokamak ă with temperature variations. Journal of Computational Physics, Elsevier, 2014, 274, pp.283-298. <10.1016/j.jcp.2014.05.025>. <hal-01464707>
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. 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), . 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
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. 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
Clothilde Colin, Patrick Tamain, Philippe Ghendrih, Frederic Schwander, Eric Serre. Impact of a Langmuir probe on turbulence measurements in the Scrape-Off-Layer of tokamaks. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.543-548. Plus de détails...
An issue for Langmuir probe measurements of SOL turbulence concerns the impact of the probe itself on plasma transport. The aim of this paper is to investigate this issue with a synthetic reconstruction of Langmuir probe measurements by inserting a synthetic probe into a 2D fluid SOL turbulence code. The effect of a biased probe is analysed as a function of its size. It is shown that the probe creates a transport barrier whose effect is non-local and affects the current's circulation in the plasma. The plasma density is depleted by the presence of the probe as well as the electrostatic potential. A strong impact on turbulence can also be observed. Such observations imply that the probed turbulence can differ significantly from the probe-free turbulence
Clothilde Colin, Patrick Tamain, Philippe Ghendrih, Frederic Schwander, Eric Serre. Impact of a Langmuir probe on turbulence measurements in the Scrape-Off-Layer of tokamaks. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.543-548. <10.1002/ctpp.201410087>. <hal-01019696>
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. 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>
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), . 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>
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. 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, Eric Serre, Frédéric Schwander, Philippe Ghendrih, Patrick Tamain. Numerical fluid modelling of the plasma edge response to a 3D object and application to mach probe measurements. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.373-377. Plus de détails...
The penalization method is used to model the interaction of 3D probe with an isothermal plasma. Density maps show that the region perturbed by the obstacle, is not restricted to its near neighbourhood, but can extend to the whole SOL. In the particular case of a probe, which is used to measure local plasma parameters, this impact can lead to violation of assumptions of locality of the perturbation usually used in determining Mach number from the imbalance in density on both sides of the probe.
Alejandro Paredes, Eric Serre, Frédéric Schwander, Philippe Ghendrih, Patrick Tamain. Numerical fluid modelling of the plasma edge response to a 3D object and application to mach probe measurements. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.373-377. <10.1002/ctpp.201410028>. <hal-01050666>
Guido Ciraolo, Hugo Bufferand, Philippe Ghendrih, Patrick Tamain, Jérome Bucalossi, et al.. Investigation of edge and SOL particle flux patterns in high density regimes using SOLEDGE2D-EIRENE code. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.432-436. Plus de détails...
We present numerical simulations of plasma transport obtained with the SOLEDGE2D code coupled to the EIRENE Montecarlo code for neutrals. We consider a double null magnetic configuration in a WEST geometry. Density and temperatures parallel profiles in the SOL domain are presented as well as Mach profile. We detail how using the penalization technique we are able to model plasma transport up to the first wall having access to energy and particle fluxes on the entire chamber wall. Moreover, we present the computed 2D contour map of the plasma mach number and of the magnitude of the ionisation source term in the whole poloidal section, emphasizing how complex and realistic geometries can be handled thanks to the penalization technique.
Guido Ciraolo, Hugo Bufferand, Philippe Ghendrih, Patrick Tamain, Jérome Bucalossi, et al.. Investigation of edge and SOL particle flux patterns in high density regimes using SOLEDGE2D-EIRENE code. Contributions to Plasma Physics, Wiley-VCH Verlag, 2014, 54 (4-6), pp.432-436. <10.1002/ctpp.201410018>. <hal-01050505>
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, . 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>
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. 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. 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>
Philippe Ghendrih, Thomas Auphan, B. Bensiali, Marco Bilanceri, K. Bodi, et al.. Divertor imbalance and divertor density regimes for ballooned cross-field turbulence. Journal of Nuclear Materials, Elsevier, 2013, 438, pp.S368-S371. . Plus de détails...
The ballooned nature of cross-field transport is shown to govern the steady state divertor imbalance of the energy flux leading to a factor 10 between the low field side and high field energy flux. An even stronger ratio is found for the divertor temperatures. Conversely the particle flux is expected to be a factor 10 larger on the high field side than on the low field side. The transition to detachment, close to divertor thermal collapse, exhibits several constraints to maintain steady state solutions. These constraints, related in particular to a large drop of the divertor density upon detachment, are shown to strongly correlate the pressure and particle flux variation along the field line and consequently the various loss channels. This delicate balance between different mechanisms is a possible understanding of the difficulty reported in detached plasma operation and simulation.
Philippe Ghendrih, Thomas Auphan, B. Bensiali, Marco Bilanceri, K. Bodi, et al.. Divertor imbalance and divertor density regimes for ballooned cross-field turbulence. Journal of Nuclear Materials, Elsevier, 2013, 438, pp.S368-S371. <http://www.sciencedirect.com/science/article/pii/S0022311513000780>. <10.1016/j.jnucmat.2013.01.070>. <hal-00920748>
A. Paredes, Hugo Bufferand, F. Schwander, G. Ciraolo, E. Serre, et al.. Penalization technique to model wall-component impact on heat and mass transport in the tokamak edge. Journal of Nuclear Materials, Elsevier, 2013, 438, pp.625-628. Plus de détails...
The original and computationally efficient volume penalization technique Ref. [1], proposed for an isothermal plasma to recover the Bohm boundary condition at the plasma–obstacle interface, is extended to model 3D obstacles. It is then generalized to handle electron and ion temperatures in a 1D model. Results in 3D simulations show that the geometry of secondary limiter has an influence on the density and particle flux profiles, breaking its toroidal symmetry and introducing profile gaps of magnitude of 20%. On the other hand, the generalization of the penalization scheme to the non-isothermal case demands to deal with new Neumann conditions on the heat fluxes. Those boundary conditions require the introduction of new mask functions to ensure that the Bohm boundary condition remains satisfied.
A. Paredes, Hugo Bufferand, F. Schwander, G. Ciraolo, E. Serre, et al.. Penalization technique to model wall-component impact on heat and mass transport in the tokamak edge. Journal of Nuclear Materials, Elsevier, 2013, 438, pp.625-628. <10.1016/j.jnucmat.2013.01.131>. <hal-01101342>
Eric Serre, M. Minguez, R. Pasquetti, E. Guilmineau, G.B. Deng, et al.. On simulating the turbulent flow around the Ahmed body: a French-German collaborative evaluation of LES and DES. Computers and Fluids, Elsevier, 2013, 78, pp.10-23. Plus de détails...
The paper presents a comparative analysis of recent simulations, conducted in the framework of a French-German collaboration on LES of Complex Flows, for the so-called Ahmed body at Reynolds number 768000 and slant angle 25°. It provides a juxtaposition of results obtained with different eddy-resolving modeling approaches, i.e. two Large Eddy Simulations (LES) on body-fitted curvilinear grids, a stabilized spectral method and a Detachted Eddy Simulation (DES) on an unstructured grid. The paper presents a comprehensive data base including both instantaneous and statistical data. A central achievement is the comparative assessment of the different approaches with an appreciation of the respective advantages and disadvantages of the various methods. In particular, issues on computational cost and ease of implementation are addressed in addition to the quality of results.
Eric Serre, M. Minguez, R. Pasquetti, E. Guilmineau, G.B. Deng, et al.. On simulating the turbulent flow around the Ahmed body: a French-German collaborative evaluation of LES and DES. Computers and Fluids, Elsevier, 2013, 78, pp.10-23. <10.1016/j.compfluid.2011.05.017>. <hal-01101350>
Hugo Bufferand, B. Bensiali, J. Bucalossi, G. Ciraolo, P. Genesio, et al.. Near wall plasma simulation using penalization technique with the transport code Soledge2D-EIRENE. Journal of Nuclear Materials, Elsevier, 2013, 438, pp.445-448. Plus de détails...
In order to model plasma interaction with full complexity of the geometry of PFCs, an immersed method to impose boundary conditions has been implemented in the transport code SolEdge2D. This penalization technique has proven to properly recover Bohm boundary conditions, including supersonic solutions at the sheath entrance. The role of the ionization source has been taken into account by coupling SolEdge2D with the 3D kinetic neutral code Eirene. Density regimes are properly recovered and major differences between core located and divertor located ionization source regimes are emphasized. One also presents main chamber wall recycling regime simulations that can now be addressed with simulations of the entire edge plasma up to the wall.
Hugo Bufferand, B. Bensiali, J. Bucalossi, G. Ciraolo, P. Genesio, et al.. Near wall plasma simulation using penalization technique with the transport code Soledge2D-EIRENE. Journal of Nuclear Materials, Elsevier, 2013, 438, pp.445-448. <10.1016/j.jnucmat.2013.01.090>. <hal-01101345>
Noele Peres, Sébastien Poncet, Eric Serre. A 3D pseudospectral method for cylindrical coordinates. Application to the simulations of rotating cavity flows. Journal of Computational Physics, Elsevier, 2012, 231, pp.6290-6305. Plus de détails...
The present work proposes a collocation spectral method for solving the three-dimensional Navier-Stokes equations using cylindrical coordinates. The whole diameter -R < r < R is discretized with an even number of radial Gauss-Lobatto collocation points and an angular shift is introduced in the Fourier transform that avoid pole and parity conditions usually required. The method keeps the spectral convergence that reduces the number of grid points with respect to lower-order numerical methods. The grid-points distribution densifies the mesh only near the boundaries that makes the algorithm well-suited to simulate rotating cavity flows where thin layers develop along the walls. Comparisons with reliable experimental and numerical results of the literature show good quantitative agreements for flows driven by rotating discs in tall cylinders and thin inter-disc cavities. Associated to a spectral vanishing viscosity [E. Séverac, E. Serre, A spectral vanishing viscosity for the LES of turbulent flows within rotating cavities, J. Comp. Phys. 226 (2007) 1234-1255], the method provides very promising LES results of turbulent cavity flows.
Noele Peres, Sébastien Poncet, Eric Serre. A 3D pseudospectral method for cylindrical coordinates. Application to the simulations of rotating cavity flows. Journal of Computational Physics, Elsevier, 2012, 231, pp.6290-6305. <10.1016/j.jcp.2012.04.033>. <hal-00822026>
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Incorporating Darcy's law for pure solvent flow through porous tubes: Asymptotic solution and numerical simulations. AIChE Journal, Wiley, 2012, 58 (7), pp.2030-2044. Plus de détails...
A generalized solution for pressure-driven, incompressible, Newtonian flow in a porous tubular membrane is challenging due to the coupling between the transmembrane pressure and velocity. To date, all analytical solutions require simplifications such as neglecting the coupling between the transmembrane pressure and velocity, assuming the form of the velocity fields, or expanding in powers of parameters involving the tube length. Moreover, previous solutions have not been validated with comparison to direct numerical simulation (DNS). We comprehensively revisit the problem to present a robust analytical solution incorporating Darcy's law on the membrane. We make no assumptions about the tube length or form of the velocity fields. The analytic solution is validated with detailed comparison to DNSs, including cases of axial flow exhaustion and cross flow reversal. We explore the validity of typical assumptions used in modeling porous tube flow and present a solution for porous channels in Supporting Information.
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Incorporating Darcy's law for pure solvent flow through porous tubes: Asymptotic solution and numerical simulations. AIChE Journal, Wiley, 2012, 58 (7), pp.2030-2044. <10.1002/aic.13823>. <hal-01032148>
Philippe Meliga, Gregory Pujals, Eric Serre. Sensitivity of 2-D turbulent flow past a D-shaped cylinder using global stability. Physics of Fluids, American Institute of Physics, 2012, 24, pp.061701. Plus de détails...
We use adjoint-based gradients to analyze the sensitivity of turbulent wake past a D-shaped cylinder at Re = 13000. We assess the ability of a much smaller control cylinder in altering the shedding frequency, as predicted by the eigenfrequency of the most unstable global mode to the mean flow. This allows performing beforehand identification of the sensitive regions, i.e., without computing the actually controlled states. Our results obtained in the frame of 2-D, unsteady Reynolds-averaged Navier-Stokes compare favorably with experimental data reported by Parezanović and Cadot [J. Fluid Mech.693, 115 (2012)] and suggest that the control cylinder acts primarily through a local modification of the mean flow profiles.
Philippe Meliga, Gregory Pujals, Eric Serre. Sensitivity of 2-D turbulent flow past a D-shaped cylinder using global stability. Physics of Fluids, American Institute of Physics, 2012, 24, pp.061701. <10.1063/1.4724211>. <hal-01061797>
Fontaine G., Poncet S., Serre E.. Multidomain extension of a divergence free pseudo-spectral algorithm for the DNS of wall-confined rotating flows. Lectures notes in comp. Sc. and Eng., 95, Springer, pp.261--271, 2012, 978-3-319-01601-6. Plus de détails...
Fontaine G., Poncet S., Serre E.. Multidomain extension of a divergence free pseudo-spectral algorithm for the DNS of wall-confined rotating flows. Lectures notes in comp. Sc. and Eng., 95, Springer, pp.261--271, 2012, 978-3-319-01601-6. <hal-01313536>
Ouafa Bouloumou, Eric Serre, Patrick Bontoux, J. Fröhlich. A 3D pseudo-spectral low Mach-number solver for buoyancy driven flows with large temperature differences. Computers and Fluids, Elsevier, 2012, 66, pp.107-120. Plus de détails...
A three-dimensional spectral method based on a Chebyshev/Chebyshev/Fourier discretization is proposed to integrate the Navier-Stokes equations for natural convection flow with large temperature differences under the low Mach-number approximation. The generalized Stokes problem arising from the time discretization by a second-order semi-implicit scheme is solved by a preconditioned iterative Uzawa algorithm. The spectrally convergent algorithm is validated on well-documented Boussinesq and non-Boussinesq benchmarks. Finally, non-Boussineq convection is investigated in a tall differentially heated cavity of aspect ratio 8 with one homogeneous direction. The technique is shown to be efficient in terms of computing performances and accuracy. The study brings new stability results evidencing 3D effects compared to both Boussinesq convection and former two-dimensional non-Boussinesq solutions. In particular, for Ra ⩾ 105 two-dimensional solutions are shown to be unstable with respect to three-dimensional perturbations. A Görtler-type instability grows in the region of the curved streamlines at both ends of the cavity and gives rise to 3D steady and oscillatory solutions. At higher Rayleigh numbers, these vortices eventually interact with a boundary layer instability leading to complex dynamics with multiple steady and unsteady stable solutions.
Ouafa Bouloumou, Eric Serre, Patrick Bontoux, J. Fröhlich. A 3D pseudo-spectral low Mach-number solver for buoyancy driven flows with large temperature differences. Computers and Fluids, Elsevier, 2012, 66, pp.107-120. <10.1016/j.compfluid.2012.05.014>. <hal-00834130>
Rodriguez S., Viaud B., Serre E.. Novel outflow boundary conditions for spectral direct numerical simulation of open rotating flows. Lectures notes in comp. Sc. and Eng., 95, Springer, pp.383--392, 2012, 978-3-319-01601-6. Plus de détails...
Rodriguez S., Viaud B., Serre E.. Novel outflow boundary conditions for spectral direct numerical simulation of open rotating flows. Lectures notes in comp. Sc. and Eng., 95, Springer, pp.383--392, 2012, 978-3-319-01601-6. <hal-01313535>
Eric Serre, Hugo Bufferand, A. Paredes, Frédéric Schwander, Guido Ciraolo, et al.. Numerical modeling of the impact of geometry and wall components on transport in the tokamak edge. Contributions to Plasma Physics, Wiley-VCH Verlag, 2012, 52 (5-6), pp.401-405. Plus de détails...
Eric Serre, Hugo Bufferand, A. Paredes, Frédéric Schwander, Guido Ciraolo, et al.. Numerical modeling of the impact of geometry and wall components on transport in the tokamak edge. Contributions to Plasma Physics, Wiley-VCH Verlag, 2012, 52 (5-6), pp.401-405. <10.1002/ctpp.201210023>. <hal-00848473>
M. Minguez, C. Brun, R. Pasquetti, E. Serre. Experimental and high-order LES analysis of the flow in near-wall region of a square cylinder. International Journal of Heat and Fluid Flow, Elsevier, 2011, 32 (3), pp.558-566. Plus de détails...
A coupled experimental/numerical analysis of turbulent flow past a square cylinder is performed at the ERCOFTAC Reynolds number Re = U∞D/ν = 21,400, where U∞ is the inflow velocity and D the cylinder height. Complementary Laser Doppler Velocimetry (LDV) and high-order large-eddy simulations (LES) approaches, based on a spectral vanishing technique (SVV-LES), provide a comprehensive data base including both instantaneous data and post-processed statistics. Beyond these results, an achievement of the paper is to investigate the coherent structures developing on the sides and in the wake of the cylinder with a special focus on the flow features in the near-wall region. The flow is found to separate at the leading edge of the cylinder with the occurence of three-dimensional Kelvin–Helmholtz (KH) pairings localized in the separating shear layer. The interaction between these KH vortical structures and Von Kármán vortex shedding (VK) in the near wake is discussed based on both visualisations and frequency analysis. In particular, signatures of VK and KH vortical structures are found on velocity time samples.
M. Minguez, C. Brun, R. Pasquetti, E. Serre. Experimental and high-order LES analysis of the flow in near-wall region of a square cylinder. International Journal of Heat and Fluid Flow, Elsevier, 2011, 32 (3), pp.558-566. <10.1016/j.ijheatfluidflow.2011.03.009>. <hal-01299962>
Journal: International Journal of Heat and Fluid Flow
Stéphane Viazzo, Sébastien Poncet, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. High-order Large Eddy Simulations of Confined Rotor-Stator Flows. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2011, 88, pp.63-75. Plus de détails...
In many engineering and industrial applications, the investigation of rotating turbulent flow is of great interest. In rotor-stator cavities, the centrifugal and Coriolis forces have a strong influence on the turbulence by producing a secondary flow in the meridian plane composed of two thin boundary layers along the disks separated by a non-viscous geostrophic core. Most numerical simulations have been performed using RANS and URANS modelling, and very few investigations have been performed using LES. This paper reports on quantitative comparisons of two high-order LES methods to predict a turbulent rotor-stator flow at the rotational Reynolds number Re=400000. The classical dynamic Smagorinsky model for the subgrid-scale stress (Germano et al., Phys Fluids A 3(7):1760-1765, 1991) is compared to a spectral vanishing viscosity technique (Séverac & Serre, J Comp Phys 226(2):1234-1255, 2007). Numerical results include both instantaneous data and postprocessed statistics. The results show that both LES methods are able to accurately describe the unsteady flow structures and to satisfactorily predict mean velocities as well as Reynolds stress tensor components. A slight advantage is given to the spectral SVV approach in terms of accuracy and CPU cost. The strong improvements obtained in the present results with respect to RANS results confirm that LES is the appropriate level of modelling for flows in which fully turbulent and transition regimes are involved.
Stéphane Viazzo, Sébastien Poncet, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. High-order Large Eddy Simulations of Confined Rotor-Stator Flows. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2011, 88, pp.63-75. <10.1007/s10494-011-9345-0>. <hal-00678841>
Stéphane Viazzo, Sébastien Poncet, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. High-order Large Eddy Simulations of Confined Rotor-Stator Flows. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2011, 88, pp.63-75. Plus de détails...
In many engineering and industrial applications, the investigation of rotating turbulent flow is of great interest. In rotor-stator cavities, the centrifugal and Coriolis forces have a strong influence on the turbulence by producing a secondary flow in the meridian plane composed of two thin boundary layers along the disks separated by a non-viscous geostrophic core. Most numerical simulations have been performed using RANS and URANS modelling, and very few investigations have been performed using LES. This paper reports on quantitative comparisons of two high-order LES methods to predict a turbulent rotor-stator flow at the rotational Reynolds number Re=400000. The classical dynamic Smagorinsky model for the subgrid-scale stress (Germano et al., Phys Fluids A 3(7):1760-1765, 1991) is compared to a spectral vanishing viscosity technique (Séverac & Serre, J Comp Phys 226(2):1234-1255, 2007). Numerical results include both instantaneous data and postprocessed statistics. The results show that both LES methods are able to accurately describe the unsteady flow structures and to satisfactorily predict mean velocities as well as Reynolds stress tensor components. A slight advantage is given to the spectral SVV approach in terms of accuracy and CPU cost. The strong improvements obtained in the present results with respect to RANS results confirm that LES is the appropriate level of modelling for flows in which fully turbulent and transition regimes are involved.
Stéphane Viazzo, Sébastien Poncet, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. High-order Large Eddy Simulations of Confined Rotor-Stator Flows. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2011, 88, pp.63-75. <10.1007/s10494-011-9345-0>. <hal-00822030>
Eric Serre, M. Minguez, R., Pasquetti, G.B. Deng, M. Kornhass, et al.. On simulating the turbulent flow around the Ahmed body : A French-German collaborative evaluation of LES and DES. Computers and Fluids, Elsevier, 2011. Plus de détails...
Eric Serre, M. Minguez, R., Pasquetti, G.B. Deng, M. Kornhass, et al.. On simulating the turbulent flow around the Ahmed body : A French-German collaborative evaluation of LES and DES. Computers and Fluids, Elsevier, 2011. <hal-01145131>
Guilhem Dif-Pradalier, J Gunn, Guido Ciraolo, C Chang, Guillaume Chiavassa, et al.. The Mistral base case to validate kinetic and fluid turbulence transport codes of the edge and SOL plasmas. Journal of Nuclear Materials, Elsevier, 2011, 415, . Plus de détails...
Experimental data from the Tore Supra experiments are extrapolated in the SOL and edge to investigate the Kelvin–Helmholtz instability. The linear analysis indicates that a large part of the SOL is rather unstable. The effort is part of the setup of the Mistral base case that is organised to validate the codes and address new issues on turbulent edges, including the comparison of kinetic and fluid modelling in the edge plasma.
Guilhem Dif-Pradalier, J Gunn, Guido Ciraolo, C Chang, Guillaume Chiavassa, et al.. The Mistral base case to validate kinetic and fluid turbulence transport codes of the edge and SOL plasmas. Journal of Nuclear Materials, Elsevier, 2011, 415, <10.1016/j.jnucmat.2010.12.035>. <cea-01468372>
Hugo Bufferand, Guido Ciraolo, Livia Isoardi, Guillaume Chiavassa, Frédéric Schwander, et al.. Applications of SOLEDGE-2D code to complex SOL configurations and analysis of Mach probe measurements. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S589-S592. Plus de détails...
A series of experiments dedicated to the determination of the ballooning nature of the edge and SOL transport has been achieved on Tore Supra and , proposing a quantitative characterization of the radial flux that enters the SOL. The aim of this paper is to back up the interpretation of these probe flow measurements making use of SOLEDGE-2D code. In particular, this fluid code allows one to study density and parallel momentum transport in a 2D geometry including edge and SOL region. Moreover, thanks to an appropriate numerical technique recently proposed and , SOLEDGE-2D code is also able to deal with a complex geometry of plasma facing components including main and secondary limiters.
Hugo Bufferand, Guido Ciraolo, Livia Isoardi, Guillaume Chiavassa, Frédéric Schwander, et al.. Applications of SOLEDGE-2D code to complex SOL configurations and analysis of Mach probe measurements. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S589-S592. <10.1016/j.jnucmat.2010.11.037>. <hal-00848483>
Livia Isoardi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, Frédéric Schwander, et al.. 2D modelling of electron and ion temperature in the plasma edge and SOL. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S574-S578. Plus de détails...
We are interested here in modelling the electron and ion temperature fields, Te and Ti respectively, in order to understand the main trends that govern the ratio Ti/Te that is being better documented in the SOL with RFA probes and . The experimental evidence gathered from several devices indicates that this temperature ratio significantly exceeds unity in most data sets that have been analysed, including measurements in the SOL of limiter devices like Tore Supra. Several issues of interest have been addressed with this version of the SOLEDGE-2D code. First, we have analysed the width of the SOL heat channels to the wall components and compared these values to analytical expressions. The key control mechanism of the width of the SOL heat channel is given by a balance between the sheath boundary conditions and the transverse transport. More advanced simulations address the interplay between the edge and SOL plasma allowing one to recover regimes with Ti/Te > 1.
Livia Isoardi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, Frédéric Schwander, et al.. 2D modelling of electron and ion temperature in the plasma edge and SOL. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S574-S578. <10.1016/j.jnucmat.2010.12.318>. <hal-00848528>
B. Viaud, Eric Serre, Jean-Marc Chomaz. Transition to turbulence through steep global-modes cascade in an open rotating cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2011, 688, pp.493-506. Plus de détails...
B. Viaud, Eric Serre, Jean-Marc Chomaz. Transition to turbulence through steep global-modes cascade in an open rotating cavity. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2011, 688, pp.493-506. <10.1017/jfm.2011.393>. <hal-00998000>
Frédéric Schwander, Guillaume Chiavassa, Guido Ciraolo, Philippe Ghendrih, Livia Isoardi, et al.. Parallel shear flow instability in the tokamak edge. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S601-S604. Plus de détails...
The transition between the core and scrape-off layer of a tokamak corresponds to a marked momentum shear layer, owing to sheath acceleration on limiters which drives near-sonic flows along the plasma magnetic field in the scrape-off layer, and a parallel shear flow instability can possibly be triggered. The possibility of this instability driven by the velocity gradient is investigated numerically, using a minimum model of particle and parallel momentum transport in the edge of a tokamak, in a computational domain modelling a limiter plasma with background turbulence modelled as an effective diffusion. It is found that unstable regions can exist in the vicinity of a limiter, in agreement with experimental findings, when momentum radial transport - and therefore coupling between SOL and core flows - is sufficiently weak. Instability is reinforced by core rotation, and is found to be maximum downstream of the limiter (with respect to the core plasma flow).
Frédéric Schwander, Guillaume Chiavassa, Guido Ciraolo, Philippe Ghendrih, Livia Isoardi, et al.. Parallel shear flow instability in the tokamak edge. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S601-S604. <10.1016/j.jnucmat.2010.10.073>. <hal-00848536>
E. Plaut, Y. Lebranchu, M. Jenny, Eric Serre. Structure and stability of annular sheared channel flows: effects of confinement, curvature and inertial forces - waves. European Physical Journal B: Condensed Matter and Complex Systems, Springer-Verlag, 2011, 79 (1), pp.35-46. Plus de détails...
The structure and stability of the flows in an annular channel sheared by a rotating lid are investigated experimentally, theoretically and numerically. The channel has a square section, and a small curvature parameter: the ratio Γ of the inter-radii to the mean radius is 9.5%. The sidewalls and the bottom of the channel are integral and can rotate independently of the lid, permitting pure shear, co-rotation and counter-rotation cases. The basic flows obtained at small shear are characterized. In the absence of co-rotation, the centrifugal force linked with the curvature of the system plays an important role, whereas, when co-rotation is fast, the Coriolis force dominates. These basic flows undergo some instabilities when the shear is increased. These instabilities lead to supercritical traveling waves in the pure shear and co-rotation cases, but to weak turbulence in the counter-rotation case. The Reynolds number for the onset of instabilities, constructed with the velocity difference between the lid and bottom at mid-radius, and the height of the channel, increases from 1000 in the counter-rotation case to 1260 in the pure shear case and higher and higher values when co-rotation increases, i.e., when the Coriolis effect increases. The relevance of uni-dimensional Ginzburg-Landau models to describe the dynamics of the waves is studied. The domain of validity of these models turns out to be quite narrow.
E. Plaut, Y. Lebranchu, M. Jenny, Eric Serre. Structure and stability of annular sheared channel flows: effects of confinement, curvature and inertial forces - waves. European Physical Journal B: Condensed Matter and Complex Systems, Springer-Verlag, 2011, 79 (1), pp.35-46. <10.1140/epjb/e2010-10572-3>. <hal-01023235>
Journal: European Physical Journal B: Condensed Matter and Complex Systems
Guillaume Chiavassa, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Hervé Guillard, et al.. Parallel expansion of density bursts. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S613-S616. Plus de détails...
Evidence of poloidally localized cross-field transport in experiments and theoretical analysis of turbulence transport governs the onset of parallel transport towards equilibrium. When cross-field transport appears in bursts, both for ELM relaxation events and microturbulence, the parallel transport of particles is shown to generate fronts that propagate with supersonic velocities. It is shown that after a short transient the density structure is no longer monotonic and that the two fronts (one co, the other counter the magnetic field) are independent. Furthermore, the time trace of the particle flux at a given location is characterized by a sharp rise followed by a longer time scale relaxation. Comparing the time delay and magnitude of the density burst at two locations allows to estimate the magnitude and the location of the generation of the front.
Guillaume Chiavassa, Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Hervé Guillard, et al.. Parallel expansion of density bursts. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S613-S616. <10.1016/j.jnucmat.2010.10.086>. <hal-00848522>
A. Paredes, Eric Serre, Livia Isoardi, Guillaume Chiavassa, Guido Ciraolo, et al.. Boundary conditions at the limiter surface obtained in the modelling of plasma wall interaction with a penalization technique. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S579-S583. Plus de détails...
Isoardi et al. [1] recently proposed a penalization technique to model solid plasma facing components that treats a solid obstacle as a sink region corresponding to the strong plasma recombination in the solid state material. A major advantage of this approach is that it produces a system that can be solved in an obstacle free domain, thus allowing the use of powerful numerical algorithms. Such a technique implemented in a minimal transport model for ionic density and parallel momentum appeared to exhibit a Mach-1 transition at the boundary layer between the plasma presheath and the limiter region. In this paper, we reconsider this result by analysing the physics of detached plasmas that are governed both by strong recombination and plasma pressure decrease, as imposed by the penalization technique within the limiter region. The analysis provides a unique control parameter A=Γcsmi/ΠA=Γcsmi/Π (Γ being the parallel particles flux, cs the sound speed, mi the ionic mass and Π the total plasma pressure) that allows one to understand the results of the penalization technique for the Mach-1 transition.
A. Paredes, Eric Serre, Livia Isoardi, Guillaume Chiavassa, Guido Ciraolo, et al.. Boundary conditions at the limiter surface obtained in the modelling of plasma wall interaction with a penalization technique. Journal of Nuclear Materials, Elsevier, 2011, 415 (1), pp.S579-S583. <10.1016/j.jnucmat.2010.12.247>. <hal-00848532>
Philippe Ghendrih, K. Bodi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, et al.. Transition to supersonic flows in the edge plasma. Plasma Physics and Controlled Fusion, IOP Publishing, 2011, 53 (5), pp.054019. Plus de détails...
With a proper choice of a single dimensionless control parameter one describes the transition between subsonic and supersonic flows as a bifurcation. The bifurcation point is characterized by specific properties of the control parameter: the control parameter has a vanishing derivative in space and takes the maximum possible value equal to 1. This method is then applied to the sheath plasma with constant temperatures, allowing one to recover the Bohm boundary condition as well as the location of the point where the bifurcation takes place. This analysis is extended to fronts, rarefaction waves and divertor plasmas. Two cases are found, those where departure from quasineutrality is mandatory to generate a maximum in the variation of the control parameter (sheath and fronts) and those where the physics of the quasineutral plasma can generate such a maximum (rarefaction waves and supersonic flow in divertors). The conditions that are required to recover the Bohm condition, when modelling the wall using the penalization technique, are also addressed and generalized.
Philippe Ghendrih, K. Bodi, Hugo Bufferand, Guillaume Chiavassa, Guido Ciraolo, et al.. Transition to supersonic flows in the edge plasma. Plasma Physics and Controlled Fusion, IOP Publishing, 2011, 53 (5), pp.054019. <10.1088/0741-3335/53/5/054019>. <hal-00848545>
Livia Isoardi, Guillaume Chiavassa, Guido Ciraolo, Pierre Haldenwang, Eric Serre, et al.. Penalization modeling of a limiter in the Tokamak edge plasma. Journal of Computational Physics, Elsevier, 2010, 229 (6), pp.2220-2235. Plus de détails...
An original penalization method is applied to model the interaction of magnetically confined plasma with limiter in the frame of minimal transport model for ionic density and parallel momentum. The limiter is considered as a pure particle sink for the plasma and consequently the density and the momentum are enforced to be zero inside. Comparisons of the numerical results with one dimensional analytical solutions show a very good agreement. In particular, presented method provides a plasma velocity which is almost sonic at the boundaries obstacles as expected from the sheath conditions through the Bohm criterion. The new system being solved in an obstacle free domain, an efficient pseudo-spectral algorithm based on a Fast Fourier transform is also proposed, and associated with an exponential filtering of the unphysical oscillations due to Gibbs phenomenon. Finally, the efficiency of the method is illustrated by investigating the flow spreading from the plasma core to the Scrape Off Layer at the wall in a two-dimensional system with one then two limiters neighboring.
Livia Isoardi, Guillaume Chiavassa, Guido Ciraolo, Pierre Haldenwang, Eric Serre, et al.. Penalization modeling of a limiter in the Tokamak edge plasma. Journal of Computational Physics, Elsevier, 2010, 229 (6), pp.2220-2235. <10.1016/j.jcp.2009.11.031>. <hal-00386101v2>
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Pressure-driven radial flow in a Taylor-Couette cell. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2010, 660, pp.527-537. Plus de détails...
A generalized solution for pressure-driven flow through a permeable rotating inner cylinder in an impermeable concentric outer cylinder, a situation used commercially in rotating filtration, is challenging due to the interdependence between the pressure drop in the axial direction and that across the permeable inner cylinder. Most previous approaches required either an imposed radial velocity at the inner cylinder or radial throughflow with both the inner and outer cylinders being permeable. We provide an analytical solution for rotating Couette-Poiseuille flow with Darcy's law at the inner cylinder by using a small parameter related to the permeability of the inner cylinder. The theory works for suction, injection and even combined suction/injection, when the axial pressure drop in the annulus is such that the transmembrane pressure difference reverses sign along the axial extent of the system. Corresponding numerical simulations for finite-length systems match the theory very well.
Nils Tilton, Denis Martinand, Eric Serre, Richard M. Lueptow. Pressure-driven radial flow in a Taylor-Couette cell. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2010, 660, pp.527-537. <10.1017/S0022112010003228>. <hal-01024690>
Brian Launder, Sébastien Poncet, Eric Serre. Laminar, transitional, and turbulent flows in rotor-stator cavities. Annual Review of Fluid Mechanics, Annual Reviews, 2010, 42 (1), pp.229-248. Plus de détails...
This article reviews the range of flows that may be created within thin cylindrical or annular cavities due to the rotation of one of the confining disks. At low Reynolds numbers, the rotation gives rise to an axisymmetric, radially outward motion near the rotor with a return flow along the stationary disk. As the Reynolds number is raised, this base flow gives way to a shear flow populated by discrete vortices, whether of cylindrical or spiral form, near both the rotating and stationary disks. At Reynolds numbers high enough for turbulent flow to occur, in the twentieth century both experimental and computational studies treated the flow as axisymmetric and steady. Recent research has shown, however, that complex organized structures also persist in the turbulent regime.
Brian Launder, Sébastien Poncet, Eric Serre. Laminar, transitional, and turbulent flows in rotor-stator cavities. Annual Review of Fluid Mechanics, Annual Reviews, 2010, 42 (1), pp.229-248. <10.1146/annurev-fluid-121108-145514>. <hal-00678846>
Sébastien Poncet, Eric Serre. High-order LES of turbulent heat transfer in a rotor–stator cavity. International Journal of Heat and Fluid Flow, Elsevier, 2009, 30, pp.590-601. Plus de détails...
The present work examines the turbulent flow in an enclosed rotor–stator system subjected to heat transfer effects. Besides their fundamental importance as three-dimensional prototype flows, such flows arise in many industrial applications but also in many geophysical and astrophysical settings. Large eddy simulations(LES) are here performed using a spectral vanishing viscosity technique. The LES results have already been favorably compared to velocity measurements in the isothermal case (Séverac et al. 2007) for a large range of Reynolds numbers in an annular cavity of large aspect ratio and weak curvature parameter. The purpose of this paper is to extend these previous results in the non-isothermal case using the Boussinesq approximation to take into account the buoyancy effects. Thus, the effects of thermal convection have been examined for a turbulent flow of air in the same rotor–stator system for Rayleigh numbers up to 100 millions. These LES results provide accurate, instantaneous quantities which are of interest in understanding the physics of turbulent flows and heat transfers in an interdisk cavity. Even at high Rayleigh numbers, the structure of the iso-values of the instantaneous normal temperature gradient at the disk surfaces resembles the one of the iso-values of the tangential velocity with large spiral arms along the rotor and more thin structures along the stator. The averaged results show small effects of density variation on the mean and turbulent fields. The turbulent Prandtl number is a decreasing function of the distance to the wall with 1.4 close to the disks and about 0.3 in the outer layers. The local Nusselt number is found to be proportional to the local Reynolds number to the power 0.7. The evolution of the averaged Bolgiano length scale with the Rayleigh number indicates that temperature fluctuations may have a large influence on the dynamics only at the largest scales of the system for Ra larger than 10 millions, since the averaged Bolgiano length scale remains lower than the thermal boundary layer thicknesses.
Sébastien Poncet, Eric Serre. High-order LES of turbulent heat transfer in a rotor–stator cavity. International Journal of Heat and Fluid Flow, Elsevier, 2009, 30, pp.590-601. <10.1016/j.ijheatfluidflow.2009.01.011>. <hal-00409169>
Journal: International Journal of Heat and Fluid Flow
Sébastien Poncet, Eric Serre, Patrice Le Gal. Revisiting the two first instabilities of the flow in an annular rotor-stator cavity. Physics of Fluids, American Institute of Physics, 2009, 21, pp.064106. Plus de détails...
Sébastien Poncet, Eric Serre, Patrice Le Gal. Revisiting the two first instabilities of the flow in an annular rotor-stator cavity. Physics of Fluids, American Institute of Physics, 2009, 21, pp.064106. <10.1063/1.3156859>. <hal-00418838>
Christine Baur, Patrick Bontoux, Michael Kornhaas, Matthieu Minguez, Richard Pasquetti, et al.. High-order methods for large-eddy simulation in complex geometries. Christophe Brun & al. Numerical simulation of turbulent flows and noise generation, Springer Berlin Heidelberg, pp.309-334, 2009, Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 978-3-540-89955-6. Plus de détails...
Developing high-order methods for large-eddy simulation (LES) is of interest to avoid mixing between subgrid scale modeling contributions and approximation errors of the numerical method. Two different approaches are investigated. The first one focuses on the so-called Spectral Vanishing Viscosity LES (SVV-LES) approach, which allows to extend the well known capabilities of spectral methods from laminar to turbulent flows, while the second one rather investigates the possibility of extending a second order finite volume code to higher order approximations. For the SVV-LES approach, a volume penalization like technique is used to address complex geometries.
Christine Baur, Patrick Bontoux, Michael Kornhaas, Matthieu Minguez, Richard Pasquetti, et al.. High-order methods for large-eddy simulation in complex geometries. Christophe Brun & al. Numerical simulation of turbulent flows and noise generation, Springer Berlin Heidelberg, pp.309-334, 2009, Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 978-3-540-89955-6. <10.1007/978-3-540-89956-3_13>. <hal-00834157>
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, Elsevier, 2009, 390-391, pp.388-391. Plus de détails...
The transition region between closed and open magnetic flux surfaces plays a crucial role for tokamak performances. Appropriate understanding of the edge region remains a major challenge owing to several open issues as momentum transport, turbulence overshoot or neutral penetration. We consider here a transport model system to investigate the propagation of parallel momentum from the SOL into the core plasma and vice-versa. The numerical results show that for small values of the radial diffusion coefficient, the density profile decays exponentially from the core to the SOL as predicted by 1D analytical solution. A spreading of the parallel momentum from the SOL to the core is observed, with the presence of non-zero velocities also in the regions far from the SOL. The effect of an imposed rotation of the core plasma is investigated as well as the dynamics of an overdensity imposed in the core plasma.
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, Elsevier, 2009, 390-391, pp.388-391. <10.1016/j.jnucmat.2009.01.088>. <hal-00848559>
Richard Pasquetti, Eric Séverac, Eric Serre, Patrick Bontoux, Michael Schaefer. From stratified wake to rotor-stator flows by a SVV-LES method. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2008, 22 (3-4), pp.261-273. Plus de détails...
Richard Pasquetti, Eric Séverac, Eric Serre, Patrick Bontoux, Michael Schaefer. From stratified wake to rotor-stator flows by a SVV-LES method. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2008, 22 (3-4), pp.261-273. <hal-01023280>
Journal: Theoretical and Computational Fluid Dynamics
R. Pasquetti, Eric Séverac, Eric Serre, Patrick Bontoux, M. Schäfer. From stratified wakes to rotor-stator flows by an SVV-LES method. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2008, 22 (3-4), pp.261-273. Plus de détails...
We extend a large-eddy simulation (LES) methodology, based on using the spectral vanishing viscosity (SVV) method to stabilize spectral collocation approximations, from the Cartesian to the cylindrical geometry. The capabilities of the SVV-LES approach are illustrated for two very different physical problems: (1) the influence of thermal stratification on the wake of a cylinder, and (2) the instabilities that develop in transitional and fully turbulent rotor-stator flows.
R. Pasquetti, Eric Séverac, Eric Serre, Patrick Bontoux, M. Schäfer. From stratified wakes to rotor-stator flows by an SVV-LES method. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2008, 22 (3-4), pp.261-273. <10.1007/s00162-007-0070-1>. <hal-00833881>
Journal: Theoretical and Computational Fluid Dynamics
Emilia Crespo del Arco, José Sanchez Alvarez, Eric Serre, A. De La Torre, Javier Burguete. Numerical and experimental study of the time dependent states and the slow dynamics in a von Karman swirling flow. Geophysical and Astrophysical Fluid Dynamics, Taylor & Francis, 2008, 103 (2), pp.1-15. Plus de détails...
Emilia Crespo del Arco, José Sanchez Alvarez, Eric Serre, A. De La Torre, Javier Burguete. Numerical and experimental study of the time dependent states and the slow dynamics in a von Karman swirling flow. Geophysical and Astrophysical Fluid Dynamics, Taylor & Francis, 2008, 103 (2), pp.1-15. <hal-01023287>
Journal: Geophysical and Astrophysical Fluid Dynamics
B. Viaud, E. Serre, Jean-Marc Chomaz. The elephant mode between two rotating disks. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2008, 598 (mars), pp.451-464. Plus de détails...
B. Viaud, E. Serre, Jean-Marc Chomaz. The elephant mode between two rotating disks. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2008, 598 (mars), pp.451-464. <10.1017/s0022112007009962>. <hal-01022811>
Eric Serre, Mathieu Minguez, Richard Pasquetti. Spectral vanishing viscosity stabilized LES of the Ahmed body turbulent wake. Communications in Computational Physics, Global Science Press, 2008, 5 (2-4), pp.635-648. Plus de détails...
Eric Serre, Mathieu Minguez, Richard Pasquetti. Spectral vanishing viscosity stabilized LES of the Ahmed body turbulent wake. Communications in Computational Physics, Global Science Press, 2008, 5 (2-4), pp.635-648. <hal-01023286>
Eric Serre, Michael Sprague, Richard Lueptow. Stability of Taylor-Couette flow with radial throughflow. Physics of Fluids, American Institute of Physics, 2008, 20 (3), pp.034106. Plus de détails...
Eric Serre, Michael Sprague, Richard Lueptow. Stability of Taylor-Couette flow with radial throughflow. Physics of Fluids, American Institute of Physics, 2008, 20 (3), pp.034106. <hal-01023284>
Bertrand Viaud, Eric Serre, Jean-Marc Chomaz. Elephant mode sitting on a rotating disk in an annulus. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2008, 598, pp.451-464. Plus de détails...
Bertrand Viaud, Eric Serre, Jean-Marc Chomaz. Elephant mode sitting on a rotating disk in an annulus. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2008, 598, pp.451-464. <hal-01023281>
Eric Séverac, Sébastien Poncet, Eric Serre, Marie-Pierre Chauve. Large eddy simulation and measurements of turbulent enclosed rotor-stator flows. Physics of Fluids, American Institute of Physics, 2007, 19 (8), pp.085113. Plus de détails...
Turbulent flows are studied in an actual enclosed rotor-stator configuration with a rotating hub and a stationary shroud. Besides its fundamental importance - the disk boundary layer is one of the simplest platforms for investigating the underlying structure of three-dimensional boundary layers - this cavity models more complex configurations relevant to rotating machinery. Large Eddy Simulation (LES) is performed using a Spectral Vanishing Viscosity (SVV) technique which is shown leading to stable discretizations without sacrificing the formal accuracy of the spectral approximation. Numerical results and velocity measurements have been favorably compared for a large range of rotational Reynolds numbers up to one million in an annular cavity of curvature parameter Rm=(b+a)/(b-a)=1.8 and of aspect ratio G=(b-a)/h=5, where a and b are respectively the inner and outer radii of the rotating disk and h is the interdisk spacing. In the detailed picture of the flow structure that emerges, the turbulence is mainly confined in the boundary layers including in the Stewartson layer along the external cylinder. For Reynolds numbers larger than 0.1 million, the stator boundary layer is turbulent over most of the cavity. On the other hand, the rotor layer becomes progressively turbulent from the outer radial locations although the rotating hub is shown to destabilize the inner part of the boundary layers. The isosurface maps of the Q-criterion reveal that the three-dimensional spiral arms observed in the unstable laminar regime evolve to more axisymmetric structures when turbulence occurs. At Re equal to one million, the flow is fully turbulent and the anisotropy invariant map highlights turbulence structuring, which can be either a ``cigar-shaped'' structuring aligned on the tangential direction or a ``pancake-shaped'' structuring depending on the axial location. The reduction of the structural parameter a1 (the ratio of the magnitude of the shear stress vector to twice the turbulence kinetic energy) under the typical limit 0.15, as well as the misalignment between the shear stress vector and the mean velocity gradient vector, highlight the three-dimensional nature of both rotor and stator boundary layers with a degree of three-dimensionality much higher than in the idealized system studied by Lygren and Andersson (2001-2006).
Eric Séverac, Sébastien Poncet, Eric Serre, Marie-Pierre Chauve. Large eddy simulation and measurements of turbulent enclosed rotor-stator flows. Physics of Fluids, American Institute of Physics, 2007, 19 (8), pp.085113. <10.1063/1.2759530>. <hal-00170072>
Eric Serre, Patrick Bontoux. Vortex breakdown in a cylinder with a rotating bottom and a flat stress-free surface. International Journal of Heat and Fluid Flow, Elsevier, 2007, 28 (2), pp.229-248. Plus de détails...
Vortex breakdown and transition to time-dependent regimes are investigated in a cylinder (H/R = 4) with a rotating disk and a free-surface. The aim of this study is to show how, by changing upstream conditions it is possible to alter on the flow, particularly the vortex breakdown process. The understanding of such effects on vortex breakdown is very useful in the development of a control strategy in order to intensify or remove the phenomenon. The flow dynamics are explored through numerical solution of the three-dimensional Navier-Stokes equations based on high-order spectral approximations. The use of a flat, stress-free model for the air/water interface is shown to be entirely satisfactory at least for moderate Reynolds numbers. A particular interest of these results is to show how the bubble related to the vortex breakdown becomes attached to the free-surface and grows in diameter as the Reynolds number is increased, Re ⩾ 2900. Such a phenomenon removes the cylindrical vortex core upstream of the breakdown which is usually included in classical theories based on idealized models of vortex flows. The flow is shown to be unstable to three-dimensional perturbations for sufficiently large rotation rates. The bifurcated state takes the form of a k = 3 rotating wave at Re = 3000. The existence of the free-surface promotes the onset of periodicity, with a critical Reynolds number about 15% lower than in the case with a rigid cover. Moreover, the successive bifurcations occur over a much shorter range of Reynolds numbers and lead rapidly to a multi-frequency regime with more than five different frequencies. In the unsteady regime, the vortex breakdown is characterized by an elongated, asymmetric recirculation zone, attached to the free-surface and precessing around the axis of the container. By increasing the rotation, the circular stagnation line on the free-surface takes a more irregular form and starts to move around the axis of the cylinder in the same sense as the rotating disk. Finally, our results show that the vertical boundary layer controls both the vortex breakdown process and the transition to unsteadiness.
Eric Serre, Patrick Bontoux. Vortex breakdown in a cylinder with a rotating bottom and a flat stress-free surface. International Journal of Heat and Fluid Flow, Elsevier, 2007, 28 (2), pp.229-248. <10.1016/j.ijheatfluidflow.2006.04.004>. <hal-00834166>
Journal: International Journal of Heat and Fluid Flow
Clemente Rodriguez, Eric Serre, Claude Rey. A numerical model for shallow-water flows: dynamics of the eddy shedding. WSEAS transactions on environment and development, 2005, 1 (2), pp.280-287. Plus de détails...
Clemente Rodriguez, Eric Serre, Claude Rey. A numerical model for shallow-water flows: dynamics of the eddy shedding. WSEAS transactions on environment and development, 2005, 1 (2), pp.280-287. <hal-01023278>
Journal: WSEAS transactions on environment and development
E. Crespo del Arco, Eric Serre, Patrick Bontoux, Brian Launder. Stability, transition and turbulence in rotating cavities. M. Rahman. Instability of flows, WIT Press, pp.141-195, 2005, Advances in Fluid Mechanics, 1-85312-785-X. Plus de détails...
This chapter reviews striking features of boundary-layer instabilities induced by different mechanisms and related to transition to turbulence in rotating flows with walls. Besides its fundamental importance as a three-dimensional prototype flow, confined flow between rotating discs has been extensively examined because of its relevance to many industrial applications such as turbomachinery and engineering processes. Many studies using stability analyses and experiments have been devoted to the onset of unstable waves and to the mechanisms associated with them. Here, we focus on how numerical investigations may provide insights and complement experimental data and analytical results by providing the full velocity field in well-controlled flows within idealized configurations. Rotor-stator and rotating cavity with radial throughflow are investigated. At a critical rotation rate, axisymmetric and/or three-dimensional structures appear in the Bödewadt and Ekman layers. All features of the transitions in these rotating cavities are documented. A comparison of the wave numbers, frequencies, and phase velocities of the instabilities with available theoretical and experimental results shows that both Type II (or A) and Type I (or B) instabilities appear, depending on flow and geometric control parameters. Interesting patterns exhibiting the coexistence of circular and spiral waves are found under certain conditions.
E. Crespo del Arco, Eric Serre, Patrick Bontoux, Brian Launder. Stability, transition and turbulence in rotating cavities. M. Rahman. Instability of flows, WIT Press, pp.141-195, 2005, Advances in Fluid Mechanics, 1-85312-785-X. <10.2495/1-85312-785-X/05>. <hal-00833957>
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich Busse. Square patterns in rotating Rayleigh-Bénard convection. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2005, 72, pp.036307. Plus de détails...
José Sanchez Alvarez, Eric Serre, Emilia Crespo del Arco, Friedrich Busse. Square patterns in rotating Rayleigh-Bénard convection. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2005, 72, pp.036307. <hal-01023277>
Journal: Physical Review E : Statistical, Nonlinear, and Soft Matter Physics
Eric Serre, Ewa Tuliszka-Sznitko, Patrick Bontoux. Coupled numerical and theoretical study of the flow transition between a rotating and stationary disk. Physics of Fluids, American Institute of Physics, 2004, 16 (3), pp.688-706. Plus de détails...
Both direct numerical simulation and theoretical stability analysis are performed together in order to study the transition process to turbulence in a flow between a rotating and a stationary disk. This linear stability analysis considers the complete rotor-stator flow and then extends the results of Lingwood [J. Fluid Mech. 299, 17 (1995); 314, 373 (1996)] obtained in a single disk case. The present linear analysis also extends the former two-disk computations of Itoh [ASME FED 114, 83 (1991)], only limited to a hydrodynamic spatial instability analysis. Moreover, in the present work, this approach is completed by discussing the effects of buoyancy-driven convection on the flow stability and by absolute/convective analysis of the flow. Coupled with accurate numerical computations based on an efficient pseudo-spectral Chebyshev-Fourier method, this study brings new insight on the spatio-temporal characteristics of this flow during the first stages of transition. For instance, an exchange of stability from a steady to a periodic flow with spiral structures is observed for the first time numerically in such cavity of large aspect ratio. The nature of the first bifurcation is discussed as well as the influence on it of disturbances coming from the end-wall boundary layer. Annular and spiral patterns are observed in the unstable stationary disk layer with characteristic parameters agreeing very well with the present theoretical results. Then, these structures are interpreted in terms of type I and type II generic instabilities. Moreover, the absolute instability regions which are supposed to be strongly connected with the turbulent breakdown process are also identified and the critical Reynolds numbers of the convective/absolute transition in both Ekman and Bödewadt layers are given.
Eric Serre, Ewa Tuliszka-Sznitko, Patrick Bontoux. Coupled numerical and theoretical study of the flow transition between a rotating and stationary disk. Physics of Fluids, American Institute of Physics, 2004, 16 (3), pp.688-706. <10.1063/1.1644144>. <hal-00838390>
Eric Serre, Patrick Bontoux, Brian Launder. Transitional-turbulent flow with heat transfer in a closed rotor-stator cavity. Journal of Turbulence, Taylor & Francis, 2004, 5, pp.008. Plus de détails...
In this paper, a non-isothermal flow confined between a rotating and a stationary disc is investigated using direct numerical simulation. Besides its fundamental importance as a three-dimensional prototype flow, such flows arise in many industrial devices, especially in turbomachinery applications. Our aim is to include the effects of density variation as this introduces a quasi-buoyant effect on the near-wall layers due to the radial acceleration, Ω2 r. None of the detailed experimental studies of disc-cavity flows has examined this effect due to the extreme flow conditions arising in an actual gas turbine. As a preliminary exploration we show here the effects on the mean flow of Rayleigh numbers up to 2 × 106. The direct numerical simulation is performed by integrating the time-dependent Navier-Stokes equations with a three-dimensional spectral method. The Boussinesq approximation is used to take into account the centrifugal-buoyancy effects. The effects of thermal convection have been examined for a transitional-turbulent flow at Re (=ΩR 1 2/ν) = 110 000 in an annular cavity of aspect ratio L (=ΔR/H) = 2.35. These DNS results provide accurate, instantaneous quantities which are of interest in understanding the physics of turbulent flow and heat transfer in a rotating disc cavity. Moreover, the averaged results show small effects of density variation and provide target data for researchers employing RANS schemes.
Eric Serre, Patrick Bontoux, Brian Launder. Transitional-turbulent flow with heat transfer in a closed rotor-stator cavity. Journal of Turbulence, Taylor & Francis, 2004, 5, pp.008. <10.1088/1468-5248/5/1/008>. <hal-00838385>
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Interaction of wavy cylindrical couette flow with endwalls. Physics of Fluids, American Institute of Physics, 2004, 16 (4), pp.1140-1148. Plus de détails...
The finite length of a Taylor-Couette cell introduces endwall effects that interact with the centrifugal instability and the subsequent wavy vortex flow. We investigate the interaction between the endwall Ekman boundary layers and the wavy vortices in a finite-length cavity via direct numerical simulation using a three-dimensional spectral method. To analyze the nature of the interaction between the vortices and the endwall layers, we consider three endwall boundary conditions: fixed endwalls, endwalls rotating with the inner cylinder, and stress-free endwalls. Near the endwalls, the waviness is diminished, primarily due to the effect of the flatness of the endwall rather than as a result of the no-slip boundary condition at the endwall. However, the waviness is present just one or two vortices away from the endwalls, indicating that the effect of the endwall on waviness does not penetrate far from the endwall. The interaction of the waviness with the endwall Ekman layer does not appear to result in disorder in the flow, either in the endwall vortex or farther from the endwall. Likewise, the waviness does not significantly alter Ekman layer thickness from that predicted based on theory
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Interaction of wavy cylindrical couette flow with endwalls. Physics of Fluids, American Institute of Physics, 2004, 16 (4), pp.1140-1148. <10.1063/1.1652671>. <hal-00836628>
Eric Serre, Ewa Tuliszka-Sznitko, Patrick Bontoux. Coupled theoretical and numerical study of the flow transition between a rotating and a stationary disk. Physics of Fluids, American Institute of Physics, 2004, 16 (3), pp.688-706. Plus de détails...
Eric Serre, Ewa Tuliszka-Sznitko, Patrick Bontoux. Coupled theoretical and numerical study of the flow transition between a rotating and a stationary disk. Physics of Fluids, American Institute of Physics, 2004, 16 (3), pp.688-706. <hal-01023275>
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Ekman vortices and the centrifugal instability in the counter-rotating cylindrical Couette flow. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2004, 18 (2-4), pp.151-168. Plus de détails...
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Ekman vortices and the centrifugal instability in the counter-rotating cylindrical Couette flow. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2004, 18 (2-4), pp.151-168. <hal-01023276>
Journal: Theoretical and Computational Fluid Dynamics
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Ekman vorticities and the centrifugal instability in counter-rotating cylindrical Couette flow. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2004, 18 (2-4), pp.151-168. Plus de détails...
The finite length of a Taylor-Couette cell introduces endwall effects that interact with the centrifugal instability. We investigate the interaction between the endwall Ekman boundary layers and the vortical structures in a finite-length cavity with counter-rotating cylinders via direct numerical simulation using a three-dimensional spectral method. To analyze the nature of the interaction between the vortices and the endwall layers we consider four endwall boundary conditions: fixed endwalls, endwalls rotating with the outer cylinder, endwalls rotating with the inner cylinder, and stress-free endwalls. The vortical structure of the flow depends on the endwall conditions. The waviness of the vortices is suppressed only very near the endwall, primarily due to zero axial velocity at the endwall rather than viscous effects. In spite of their waviness and random behavior, the vortices generally stay inside of the vθ=0 isosurface by adjusting quickly to the radial transport of azimuthal momentum. The thickness and strength of the Ekman layer at the endwall match with that predicted from a simple theoretical approach.
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Ekman vorticities and the centrifugal instability in counter-rotating cylindrical Couette flow. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2004, 18 (2-4), pp.151-168. <10.1007/s00162-004-0140-6>. <hal-00838377>
Journal: Theoretical and Computational Fluid Dynamics
Eric Serre, Peter Stansby, Dominique Laurence, Brian Launder. Ecoulement autour d'un modèle d'île conique en eau peu profonde, Revue Européenne des Eléments Finis. Revue Européenne des Eléments Finis, Hermès, 2003, 12 (2-3), pp.361-371. Plus de détails...
Eric Serre, Peter Stansby, Dominique Laurence, Brian Launder. Ecoulement autour d'un modèle d'île conique en eau peu profonde, Revue Européenne des Eléments Finis. Revue Européenne des Eléments Finis, Hermès, 2003, 12 (2-3), pp.361-371. <hal-01023273>
P. Droll, M. Schafer, Eric Serre, Patrick Bontoux. An implicit pseudospectral multi-domain method for the simulation of incompressible flows. International Journal for Numerical Methods in Fluids, Wiley, 2003, 41 (5), pp.447-470. Plus de détails...
A pseudo-spectral method for the solution of incompressible flow problems based on an iterative solver involving an implicit treatment of linearized convective terms is presented. The method allows the treatment of moderately complex geometries by means of a multi-domain approach and it is able to cope with non-constant fluid properties and non-orthogonal problem domains. In addition, the fully implicit scheme yields improved stability properties as opposed to semi-implicit schemes commonly employed. Key components of the method are a Chebyshev collocation discretization, a special pressure-correction scheme, and a restarted GMRES method with a preconditioner derived from a fast direct solver. The performance of the proposed method is investigated by considering several numerical examples of different complexity, and also includes comparisons to alternative solution approaches based on finite-volume discretizations.
P. Droll, M. Schafer, Eric Serre, Patrick Bontoux. An implicit pseudospectral multi-domain method for the simulation of incompressible flows. International Journal for Numerical Methods in Fluids, Wiley, 2003, 41 (5), pp.447-470. <10.1002/fld.441>. <hal-00838397>
Journal: International Journal for Numerical Methods in Fluids
Said Benjeddou, Eric Serre, Claude Rey. Application de l'approximation polytropique à la simulation numérique directe d'écoulements de gaz chauds. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2003, 332, pp.271-277. Plus de détails...
Said Benjeddou, Eric Serre, Claude Rey. Application de l'approximation polytropique à la simulation numérique directe d'écoulements de gaz chauds. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2003, 332, pp.271-277. <hal-01023274>
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Interaction between the Ekman pumping and the centrifugal instability in Taylor-Couette flow. Physics of Fluids, American Institute of Physics, 2003, 15 (2), pp.467-477. Plus de détails...
The endwalls in a Taylor-Couette cell introduce adjacent boundary layers that interact with the centrifugal instability. We investigate the interaction between the endwall Ekman layers and the Taylor vortices near transition from nonvortical to vortical flow via direct numerical simulation using a spectral method. We consider a radius ratio of η = 0.75 in a short annulus having a length-to-gap ratio of Γ = 6. To analyze the nature of the interaction between the vortices and the endwall layers, three endwall boundary conditions were considered: fixed endwalls, endwalls rotating with the inner cylinder, and stress-free endwalls. Below the critical Taylor number, endwall vortices for rotating endwalls are more than twice the strength of the vortices for fixed endwalls. This trend continues well above the transition to vortical flow, consistent with a simple force balance analysis near the endwalls. Stress-free endwalls result in endwall vortices that are similar in strength to those for rotating endwalls above the critical Taylor number. The endwall conditions significantly change the bifurcation diagram based on the radial velocity near the center of the annulus. For stress-free endwall conditions, the bifurcation is quite sharp, although only one fork of the bifurcation results unless the initial conditions are specifically set to favor the other fork. For rotating and fixed endwalls, there is a continuous transition from a featureless flow to a vortical flow due to the endwall vortices.
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Interaction between the Ekman pumping and the centrifugal instability in Taylor-Couette flow. Physics of Fluids, American Institute of Physics, 2003, 15 (2), pp.467-477. <10.1063/1.1534108>. <hal-00838408>
Eric Serre, Patrick Bontoux, Brian Launder. Direct numerical simulation of transitional turbulent flow in an enclosed rotor-stator cavity. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2002, 69 (1), pp.35-50. Plus de détails...
The transitional turbulent regime in confined flow between a rotating and a stationary disc is studied using direct numerical simulation. Besides its fundamental importance as a three-dimensional prototype flow, such flows frequently arise in many industrial devices, especially in turbomachinary applications. The present contribution extends the DNS simulation into the turbulent flow regime, to a rotational Reynolds number Re =3 × 105. An annular rotor-stator cavity of radial extension ΔR and height H, is considered with L = 4.72(L = ΔR/H) and Rm = 2.33 (Rm = (R 1+ R 0)/ΔR). The direct numerical simulation is performed by integrating the time-dependent Navier-Stokes equations until a statistically steady state is reached. A three-dimensional spectral method is used with the aim of providing both very accurate instantaneous fields and reliable statistical data. The instantaneous quantities are analysed in order to enhance our knowledge of the physics of turbulent rotating flows. Also, the results have been averaged so as to provide target turbulence data for any subsequent modelling attempts at reproducing the flow.
Eric Serre, Patrick Bontoux, Brian Launder. Direct numerical simulation of transitional turbulent flow in an enclosed rotor-stator cavity. Flow, Turbulence and Combustion, Springer Verlag (Germany), 2002, 69 (1), pp.35-50. <10.1023/A:1022467232348>. <hal-00838458>
Isabelle Raspo, Sandrine Hugues, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. A spectral projection method for the simulation of complex three-dimensional rotating flows. Computers and Fluids, Elsevier, 2002, 31 (4-7), pp.745-767. Plus de détails...
In this paper, we present an efficient projection method to solve the three-dimensional time-dependent incompressible Navier-Stokes equations in primitive variables formulation using spectral approximations. This method is based on a modification of the algorithm proposed by Goda [J. Comp. Phys. 30 (1979) 76]. It brings an improvement by introducing a preliminary step for the pressure in order to allow a temporal evolution of the normal pressure gradient at the boundaries. Its efficiency is brought to the fore by comparison with the Goda's algorithm. The modified projection method is then applied to the simulation of complex three-dimensional flows in rotating cavities, involving either a throughflow or a differential rotation.
Isabelle Raspo, Sandrine Hugues, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. A spectral projection method for the simulation of complex three-dimensional rotating flows. Computers and Fluids, Elsevier, 2002, 31 (4-7), pp.745-767. <10.1016/S0045-7930(01)00070-6>. <hal-00833836>
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Spiral and wavy vortex flows in short counter-rotating Taylor-Couette cells. International Journal of Theoretical and Computational Fluid dynamics, 2002, 16, pp.5-15. Plus de détails...
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Spiral and wavy vortex flows in short counter-rotating Taylor-Couette cells. International Journal of Theoretical and Computational Fluid dynamics, 2002, 16, pp.5-15. <hal-01023184>
Journal: International Journal of Theoretical and Computational Fluid dynamics
Eric Serre, Patrick Bontoux. Vortex breakdown in a three-dimensional swirling flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2002, 459, pp.347-370. Plus de détails...
Eric Serre, Patrick Bontoux. Vortex breakdown in a three-dimensional swirling flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2002, 459, pp.347-370. <hal-01023166>
Eric Serre, Serge Gauthier. An auto-adative multidomain pseudo-spectral technique for linear stability analysis: application to viscous compressible flows. Journal of Scientific Computing, Springer Verlag, 2002, 17 (1-4), pp.91-99. Plus de détails...
Eric Serre, Serge Gauthier. An auto-adative multidomain pseudo-spectral technique for linear stability analysis: application to viscous compressible flows. Journal of Scientific Computing, Springer Verlag, 2002, 17 (1-4), pp.91-99. <hal-01023182>
Ewa Tuliszka-Sznitko, Eric Serre, Patrick Bontoux. On the nature of the boundary layer instability in a closed rotor-stator cavity. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2002, 329, pp.91-99. Plus de détails...
Ewa Tuliszka-Sznitko, Eric Serre, Patrick Bontoux. On the nature of the boundary layer instability in a closed rotor-stator cavity. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2002, 329, pp.91-99. <hal-01023180>
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Spiral and wavy vortex flows in short counter-rotating Taylor-Couette cells. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2002, 16 (1), pp.5-15. Plus de détails...
Differentially rotating cylinders result in a rich variety of vortical flows for cylindrical Couette flow. In this study we investigate the case of a short, finite-length cavity with counter-rotating cylinders via direct numerical simulation using a three-dimensional spectral method. We consider aspect ratios ranging from 5 to 6. Two complex flow regimes, wavy vortices and interpenetrating spirals, occur with similar appearance to those found experimentally for much larger aspect ratios. For wavy vortices the wave speed is similar to that found for counter-rotating systems and systems in which the outer cylinder is stationary. For the interpenetrating spiral structure, the vortices are largely confined to the unstable region near the inner cylinder. The endwalls appear to damp and stabilize the flow as the aspect ratio is reduced to the point that in some cases the vortical flow is suppressed. At higher inner cylinder speeds, the interpenetrating spirals acquire a waviness and the vortices, while generally near the inner cylinder, can extend all of the way to the outer cylinder.
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Spiral and wavy vortex flows in short counter-rotating Taylor-Couette cells. Theoretical and Computational Fluid Dynamics, Springer Verlag, 2002, 16 (1), pp.5-15. <10.1007/s00162-002-0070-0>. <hal-00833861>
Journal: Theoretical and Computational Fluid Dynamics
Isabelle Raspo, Sandrine Hugues, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. Spectral projection methods for the simulation of complex three-dimensional rotating flows. Computers and Fluids, Elsevier, 2002, 31 (4-7), pp.745-767. Plus de détails...
Isabelle Raspo, Sandrine Hugues, Eric Serre, Anthony Randriamampianina, Patrick Bontoux. Spectral projection methods for the simulation of complex three-dimensional rotating flows. Computers and Fluids, Elsevier, 2002, 31 (4-7), pp.745-767. <hal-01023173>
Eric Serre, Patrick Bontoux. Vortex breakdown in a three-dimensional swirling flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2002, 459, pp.347-370. Plus de détails...
Time-dependent swirling flows inside an enclosed cylindrical rotor-stator cavity with aspect ratio H/R = 4, larger than the ones usually considered in the literature, are studied. Within a certain range of governing parameters, vortex breakdown phenomena can arise along the axis. Very recent papers exhibiting some particular three-dimensional effects have stimulated new interest in this topic. The study is carried out by a numerical resolution of the three-dimensional Navier-Stokes equations, based on high-order spectral approximations in order to ensure very high accuracy of the solutions. The first transition to an oscillatory regime occurs through an axisymmetric bifurcation (a supercritical Hopf bifurcation) at Re = 3500. The oscillatory regime is caused by an axisymmetric mode of centrifugal instability of the vertical boundary layer and the vortex breakdown is axisymmetric, being composed of two stationary bubbles. For Reynolds numbers up to Re = 3500, different three-dimensional solutions are identified. At Re = 4000, the flow supports the k = 5 mode of centrifugal instability. By increasing the rotation speed to Re = 4500, the vortex breakdown evolves to an S-shaped type after a long computational time. The structure is asymmetric and gyrates around the axis inducing a new time-dependent regime. At Re = 5500, the structure of the vortex breakdown is more complex: the upper part of the structure takes a spiral form. The maximum rotation speed is reached at Re = 10000 and the flow behaviour is now chaotic. The upper structure of the breakdown can be related to the spiral-type. Asymmetric flow separation on the container wall in the form of spiral arms of different angles is also prominent.
Eric Serre, Patrick Bontoux. Vortex breakdown in a three-dimensional swirling flow. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2002, 459, pp.347-370. <10.1017/S0022112002007875>. <hal-00838446>
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, Elsevier, 2001, 22 (1), pp.82-93. Plus de détails...
Eric Serre, Sandrine Hugues, Emilia Crespo del Arco, Anthony Randriamampianina, Patrick Bontoux. Axisymmetric and three-dimensional instabilities in an Ekman boundary layer flow. International Journal of Heat and Fluid Flow, Elsevier, 2001, 22 (1), pp.82-93. <hal-01023080>
Journal: International Journal of Heat and Fluid Flow
Eric Serre, Emilia Crespo del Arco, Patrick Bontoux. Annular and spiral patterns in flows between rotating and stationary discs. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2001, 434, pp.65-100. Plus de détails...
Different instabilities of the boundary layer flows that appear in the cavity between stationary and rotating discs are investigated using three-dimensional direct numerical simulations. The influence of curvature and confinement is studied using two geometrical configurations: (i) a cylindrical cavity including the rotation axis and (ii) an annular cavity radially confined by a shaft and a shroud. The numerical computations are based on a pseudo-spectral Chebyshev{Fourier method for solving the incompressible Navier{Stokes equations written in primitive variables. The high level accuracy of the spectral methods is imperative for the investigation of such instability structures. The basic flow is steady and of the Batchelor type. At a critical rotation rate, stationary axisymmetric and/or three-dimensional structures appear in the B¨odewadt and Ekman layers while at higher rotation rates a second transition to unsteady flow is observed. All features of the transitions are documented. A comparison of the wavenumbers, frequencies, and phase velocities of the instabilities with available theoretical and experimental results shows that both type II (or A) and type I (or B) instabilities appear, depending on flow and geometric control parameters. Interesting patterns exhibiting the coexistence of circular and spiral waves are found under certain conditions.
Eric Serre, Emilia Crespo del Arco, Patrick Bontoux. Annular and spiral patterns in flows between rotating and stationary discs. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2001, 434, pp.65-100. <hal-01023110>
Eric Serre, Isabelle Raspo, Patrick Bontoux, Roger Peyret. Spectral solutions of the Navier-Stokes equations for rotating flow,. ZAMM, Wiley-VCH Verlag, 2001, 81 (1), pp.533-536. Plus de détails...
Eric Serre, Isabelle Raspo, Patrick Bontoux, Roger Peyret. Spectral solutions of the Navier-Stokes equations for rotating flow,. ZAMM, Wiley-VCH Verlag, 2001, 81 (1), pp.533-536. <hal-01023113>
Eric Serre, Jean-Pierre Pulicani. A 3D pseudospectral method for rotating flows is a cylinder. Computers and Fluids, Elsevier, 2001, 30 (4), pp.491-519. Plus de détails...
Eric Serre, Jean-Pierre Pulicani. A 3D pseudospectral method for rotating flows is a cylinder. Computers and Fluids, Elsevier, 2001, 30 (4), pp.491-519. <hal-01024303>
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Identification of complex flows in Taylor-Couette counter-rotating cavities. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2001, 329 (10), pp.727-733. Plus de détails...
The transition in confined rotating flows is a topical problem with many industrial and fundamental applications. The purpose of this study is to investigate the Taylor-Couette flow in a finite-length cavity with counter-rotating walls, for two aspect ratios L=5 or L=6. Two complex regimes of wavy vortex and spirals are emphasized for the first time via direct numerical simulation, by using a three-dimensional spectral method. The spatio-temporal behavior of the solutions is analyzed and compared to the few data actually available.
Olivier Czarny, Eric Serre, Patrick Bontoux, Richard M. Lueptow. Identification of complex flows in Taylor-Couette counter-rotating cavities. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, Elsevier, 2001, 329 (10), pp.727-733. <10.1016/S1620-7742(01)01392-7>. <hal-00835783>
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
