ERCOFTAC Bulletin 77Presentation of the main activities of the MSNM-GP laborator

Bontoux, Patrick

Ciraolo, Guido

Morvan, Dominique

Poncet, Sébastien

Serre, Eric

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France South Pilot Centre - Main activities of the MSNM-GP laboratory

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France South Pilot Centre - Main activities of theMSNM-GP laboratorySe´bastien Poncet, Patrick Bontoux, Guido Ciraolo, Dominique Morvan, EricSerreTo cite this version:Se´bastien Poncet, Patrick Bontoux, Guido Ciraolo, Dominique Morvan, Eric Serre. FranceSouth Pilot Centre - Main activities of the MSNM-GP laboratory. ERCOFTAC Bulletin 77.2008. <hal-00678937>HAL Id: hal-00678937https://hal.archives-ouvertes.fr/hal-00678937Submitted on 14 Mar 2012HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.Main activities of the MSNM-GP laboratorySe´bastien Poncet, Patrick Bontoux, Guido Ciraolo, Dominique Morvan, E´ric SerreLaboratoire MSNM-GP, UMR 6181 Universite´s d’Aix-Marseille,Technopoˆle Chaˆteau-Gombert, 38 rue Joliot-Curie, 13451 Marseille, France1 IntroductionIn January 2008, the MSNM-GP laboratory will becomposed of about 54 permanent persons - corre-sponding to 46 researchers and faculty members, 8staff and engineers - plus about 30 PhD students andpost-doctorates. The laboratory is organized in twoDepartments - Computational Fluid Mechanics andof Chemical engineering - that cover nearly 60% and40%, respectively. It is mainly located in two sitesin the campus of Ecole Centrale de Marseille - IMTChaˆteau-Gombert - and in the campus of Arbois -north of Marseille. The MSNM-GP laboratory cov-ers a wide range of topics mainly relevant to fluidsdynamics and transfer, of high order accurate approx-imations and of high performance computing.The activities of the group of heat transfer and re-active flows involves topics as the modelling and phys-ical investigation of instabilities in combustion [10],the simulation of fire expansion in natural (forest)sites [6, 7] and the combined numerical and exper-imental (with industrial companies) study of smokeexpansion and heat transfer in tunnels during fires.Many topics concern the understanding of fluid flowand heat transfer processes in microgravity environ-ment (CNES) - as for instance, the hydrodynamicsof supercritical fluids (pure CO2 or binary mixtures[8]) and flow regimes, the convection and thermal dis-tribution of species inside a closed cabin [4] . . . Thesupercritical fluid flow topic [1] has also an impact inthe control of processes as crystallisation inside sol-vents included in processes in junction with one of theteam of the Chemical engineering Department (ESAprogram) [9]. This (mainly experiments oriented) de-partment also involves teams acting in the membraneand filtration processes and in the treatment of wastewater and it has an important role in the collabora-tive work with industries.The Fluid Mechanics Department is involved inthe modelling and simulation of instabilities, transi-tional and turbulent flows in internal and externaldevices. The more recent contributions concern theinvestigation of the vortex breakdown in a cylinderwith a rotating bottom and a free surface [13] andalso the investigation of LES based on special mod-elling issued for the spectral vanishing viscosity model[15] and using a penalization method (in strong linkwith the J.A. Dieudonne´ laboratory, R. Pasquetti)and Tech. Uni. Darmstadt (frame GDR Europe´enMFN, CNRS-DFG, M. Scha¨fer). The Coherent Vor-tex Simulation CVS has been extended to large sizecomputational problem and the wavelet approach wasdevelopped in the frame of the simulation of plasmasflows in the occurrence of a magnetic field for ITERapplication in the frame of CEA and ANR program.A LRC laboratory network between CEA, Ecole Cen-trale Marseille and Universite´ d’Aix-Marseille was re-cently constituted between a team of the laboratoryand the DRFC of Cadarache on CFD modelling insideITER research program. The list is not exhaustiveand some topics are reported and illustrated withinthis review.2 Aerodynamics of externaland internal flows with highorder methods2.1 Ahmed bodyA numerical study of the flow over the Ahmed carmodel (Ahmed body [2], see Fig.1 & 2), with slantedback-face 25◦, is provided in collaboration with R.Pasquetti (Lab. J. Dieudonne´, Nice) for a Reynoldsnumber Re = 768000. It constitutes a flow at veryhigh Reynolds number and massive separation. Thestudy is based on a high-order large-eddy simula-tions (LES), carried out with a multi-domain spec-tral Chebyshev-Fourier solver. The LES capabilityis implemented thanks to a Spectral Vanishing Vis-cosity (SVV) technique, with particular attention tothe near-wall region, and the bluff body is modeledwith a pseudopenalization method. Such a SVV-LESapproach is extended for the first time to an indus-trial three-dimensional turbulent flow over a complexgeometry. A detailed analysis of the flow structuresprovides a better understanding of the interactionsbetween flow separations and the dynamic behaviorof the released vortex wake.Figure 1: 3D streamline patterns colored by the lon-gitudinal velocity < u >.The complex dynamics of the wake flow is recov-ered in agreement with the experimental results ofLienhart et al. [5]. The thin turbulent boundarylayer partially separates at the edge of the slant in-1volving highly unsteady turbulent mechanisms abovethe slanted face and in the wake. The present SVV-LES results have shown that this partial detachmentis controlled by two strong contra rotative trailingvortices (Fig.1) which interact with hairpin vorticesoccurring within the shear layer above the slant toform large helical structures providing strong un-steady phenomena in the wake (Fig.2). More intrin-sic properties of the turbulence was pointed out asthe k5/3 energy density decay in the inertial range.Comparisons of the time averaged quantities havealso shown a globally good quantitative agreementwith experimental [5] measurements in the symmetryplane. An original near wall treatment based on alocal relaxation of the SVV threshold has been imple-mented, which has considerably improved the resultsand particularly the production of turbulence over theslant. An improvement of the present results wouldcome from a better prediction of the upstream flowover the roof of the body.Figure 2: Iso-values of pressure fluctuations coloredby < u >.2.2 Rotating disk flowsFlows in rotating-disk systems are not only a sub-ject of fundamental interest as prototype flows forinvestigating the underlying structures of the three-dimensional laminar and turbulent boundary layersbut are also a topic of practical importance in the per-formance improvements of many industrial devices.Moreover, many of these flows have also features thatappear in the flows in the Earth atmosphere and inwind-driven surface layers of the ocean.Turbulent flows have been considered in an ac-tual enclosed rotor-stator configuration with a rotat-ing hub and a stationary shroud. Large Eddy Simu-lations (LES) have been performed using the Spec-tral Vanishing Viscosity (SVV) technique which isshown leading to stable discretizations without sacri-ficing the formal accuracy of the spectral approxima-tion [15]. The numerical results have been favorablycompared to velocity measurements performed at IR-PHE (Marseille) for rotational Reynolds numbers upto Re = 106 in an annular cavity of large aspect ra-tio [14]. In the detailed picture of the flow struc-ture that emerges, the turbulence is mainly confinedin the boundary layers including in the StewartsonFigure 3: Isosurface plot of the Q-criterion in therotor boundary layer for Re = 106.layer along the external cylinder. For Reynolds num-bers Re ≥ 105, the stator boundary layer is turbulentover most of the cavity. On the other hand, the rotorlayer becomes progressively turbulent from the outerradial locations although the rotating hub is shownto destabilize the inner part of the boundary layers.The isosurface maps of the Q-criterion reveal that thethree-dimensional spiral arms (Fig.3) observed in theunstable laminar regime evolve to more axisymmet-ric structures when turbulence occurs. At Re = 106,the flow is fully turbulent and the anisotropy invari-ant map highlights turbulence structuring, which canbe either a “cigar-shaped” structuring aligned on thetangential direction or a “pancake-shaped” structur-ing depending on the axial location. The reduction ofthe structural parameter (the ratio of the magnitudeof the shear stress vector to twice the turbulence ki-netic energy) under the typical limit 0.15, as well asthe misalignment between the shear stress vector andthe mean velocity gradient vector, highlight the three-dimensional nature of both rotor and stator bound-ary layers with a degree of three-dimensionality muchhigher than in previous open systems.These last results have been extended to the non-isothermal case. The Boussinesq approximation isused to take into account the centrifugal-buoyancy ef-fects. The thermal effects have been examined in thesame rotor-stator cavity for Re = 106 and Rayleighnumbers up to Ra = 108. These LES results provideaccurate, instantaneous quantities which are of inter-est in understanding the physics of turbulent flowsand heat transfers in such cavities. At Ra = 107, aregime with thermal plumes appear but regarding theaveraged results, very small effects of density varia-tion are obtained on the mean and turbulent fields.The radial distributions of the local Nusselt numberNu on both disks confirm previous results: Nu de-pends on the local Reynolds number to the power αslightly lower than 0.8 (α = 0.746 here).Experiments performed in collaboration with Pro-fessor B.E. Launder (MACE, Univ. Manchester) [3]have revealed the appearance at very high Reynoldsnumbers of three-dimensional structures in the coreregion of the flow in enclosed rotor-stator cavities ofvery large aspect ratio. These have been confirmed byrecent experiments for other flow conditions. Theseorganized vortex structures play a significant role onthe entire flow - so that (U)RANS simulations can2(a) (b)Figure 4: Visualizations by dye injection of 3D struc-tures in the core region of a highly turbulent rotor-stator flow: (a) S-shaped mode, (b) three-vortexmode [3].fail to predict accurately the heat transfer in thesecavities. The two-vortex S-shaped (Fig.3a) and thethree-vortex (Fig.3b) patterns are stable over a widerange of conditions but higher modes have also beenobserved. These structures disappear when a rotatinghub is attached to the stationary disk, which explainswhy they have not been obtained in the previous LEScalculations.3 Computational Approachesof Magnetized Plasmas FlowsSince 2005 the laboratory is involved in a research ac-tivity on numerical modelling of turbulence for toka-mak fusion plasma. This activity is performed in col-laboration with the “De´partement de Recherche surla Fusion Controˆle´e” (DRFC) of the CEA-Cadarache,in the framework of the ITER project. The ANR andLRC projects mentioned above are focused on twomain research activities that are briefly described inthe following.3.1 Multiscale methods for computingfluid and plasma turbulenceThe group in collaboration with M. Farge (LMD,ENS Paris) develops multiscale methods for model-ing and computing fully-developped turbulent flows.The idea is to decompose the flow variables into co-herent and incoherent contributions using nonlinearwavelet filtering. The coherent part is then determin-istically integrated using adaptive numerical methodswhile the influence of the incoherent background flowis statistically modeled. The new method, called Co-herent Vortex Simulation (CVS) has been successfullyapplied, for examples, to compute turbulent mixinglayers or decaying two-dimensional turbulence [12] ina circular container [11] (Fig.5). To compute confinedflows or flows around obstacles, the CVS method isassociated with a voluminal penalty method. Thiscombined approach has been successfully applied totwo-dimensional flows such as the flow behind a flatwing, in a network of tubes . . .3.2 Numerical modelling of turbu-lence transport equations for toka-mak edge plasmasThe confinement performances of tokamak plasmasare essentially governed by turbulent transport. Inthis framework, the transition region between closedFigure 5: Decaying 2D turbulence in a circular con-tainer: vorticity field [11].and open magnetic flux surfaces plays a crucialrole. Indeed, an edge transport barrier can developspontaneously in its vicinity, leading to the so-calledH-mode regime. This is the reference scenario forITER, and such will focus the research effort priorand during ITER operation.Our collaboration with the DRFC/CEA-Cadarache concerns more specifically the studyof the edge region in which several open issuesremain. First, there is a rich variety of non linearphysical processes that are potentially importantin this region, ranging from turbulence overshootto neutral penetration. Second, the very sharptransition in this region is a challenge to manyconcepts used to describe transport properties. Also,the instability mechanisms are shown to changecompletely there. This leads to a complex boundarylayer problem. Third, and not surprisingly, thenon linear simulations of fluid equations require apowerful numerical treatment that is able to accountsimultaneously for the doubly-periodic (inner) regionand the essentially non-periodic (outer) region.This collaboration is related to the work startedwith the ANR contract: M2TFP (“De´veloppementde Me´thodes Multi-e´chelles et spectrales pourl’analyse et la simulation nume´rique en TurbulenceFluide et Plasma. Application a` la fusion dans lesplasmas avec confinement magne´tique”, 2006-2008).4 Fire modelling and simula-tionFor ten years, the team develops researches activityin wildfire modelling [6, 7]. They participated, in col-laboration with the IUSTI laboratory in Marseille,to three European projects (EFAISTOS, FIRESTARand EUFIRELAB) during the 4th and the 5th Frame-work Programs (FP). Actually they participate (asthe main member of the Consortium) to the Euro-pean project FireParadox (6th FP). Inside this fouryears project (March 2006 - February 2010), theyare in charge to develop a 3D code to simulate thebehaviour of wildfires at a local scale (< 500 m)(see Fig.6a,b). This work is an extension of a 2Dmodel that they have developed this last decade. Itis based on a multiphase formulation, describing themain physical phenomena governing the propagationof a fire through a solid fuel layer. During this project,a particular effort is done to optimise and to adapt3the computational code to the multi-processor sharememory machines (SGI-Altix) bought with the finan-cial support of the European commission.(a)(b)Figure 6: (a) Average temperature field calculatedduring the propagation of a surface fire through aMediterranean shrubland; (b) Surface fire in a shrub-land: Evolution of the rate of spread (ROS) as a func-tion of the wind speed (numerical results comparedwith experimental correlations).5 Others, international net-works and web-sitesComplementary details on other activities in theMSNM-GP (L3M) laboratory are available in theweb site : http://www.MSNM-GP.univ-mrs.fr/.The CNRS-DFG Program headed in the frame ofGDR Europe´en MFN directly involves 30 laboratoriesand research teams in France and Germany amongthem three participating to ERCOFTAC France SudGroup - that are MSNM-GP UMR 6181, Lab. J.A.Dieudonne´ UMR 6621 (Nice, R. Pasquetti), IMFTUMR 5502 (Toulouse, Ch. Airiau).References on the two research topics inweb sites : Generation of Noise in TurbulentFlows (http://www.iag.uni-stuttgart.de/dfg-cnrs/)and LES of Complex Flows(http://www.hy.bv.tum.de/DFG-CNRS/).References[1] G. Accary, and I. Raspo. A 3D finite volumemethod for the prediction of a supercritical fluidboyant flow in a differentially heated cavity. Com-puters & Fluids, 35 (10):1316–1331, 2006.[2] S.R. Ahmed, and G. Ramm. Salient Features ofthe Time-Averaged Ground Vehicle Wake. SAE-paper, 40300, 1984.[3] O. Czarny, H. Iacovides and B.E. Launder. Pre-cessing Vortex Structures in Turbulent Flowwithin Rotor-Stator Disc Cavities. Flow, Turbu-lence and Combustion, 69:51–61, 2002.[4] M. Forestier & P. Haldenwang. Analysis of highRayleigh number thermally stratified convectionthat affects the vapour phase in a liquefied gasstorage tank. J. Fluid Mech., 588:217–241, 2007.[5] H. Lienhart, C. Stoots, and S. Becker. Flow andturbulence structures in the wake of a simplifiedcar model (Ahmed Body). In DGLR Fach Symp.der AG STAB, Stuttgart University, 15-17 No-vember 2000.[6] D. Morvan, and J.L. Dupuy. Modelling the prop-agation of a wildfire through a Mediterraneanshrub using a multiphase formulation. Combus-tion & Flame, 138:199–200, 2004.[7] D. Morvan. A numerical study of flame geom-etry and potential for crown fire initiation for awildfire propagating through a shrub fuel. Int. J.Wildland Fire, 16:511–518, 2007.[8] I. Raspo, S. Meradji & B. Zappoli. Heterogeneousreaction induced by the piston effect in supercrit-ical binary mixtures. Chem. Eng. Sci., 62:4182–4192, 2007.[9] I. Raspo, C. Nicolas, E. Neau & S. Meradji. Dif-fusion of solids in supercritical carbon dioxide :Modelling of near critical behaviour. Fluid PhaseEquilib., in press, 2007.[10] O. Roussel, and K. Schneider. Adaptive numeri-cal simulation of pulsating planar flames for largeLewis and Zeldovich ranges. Comm. Nonlin. Sci.Num. Simulation, 11:463–480, 2006.[11] K. Schneider, and M. Farge. Decaying two-dimensional turbulent flow in a circular container.Phys. Rev. Lett., 95:244502, 2005.[12] K. Schneider, M. Farge, A. Azzalini & J. Ziuber.Coherent vortex extraction and simulation of 2Disotropic turbulence. JoT, 7 (44):1–24, 2006.[13] E. Serre & P. Bontoux. Vortex breakdown in acylinder with a rotating bottom and a free surface.Int. J. Heat Fluid Flow, 28 (2):229–248, 2007.[14] E. Se´verac, S. Poncet, E. Serre and M.P. Chauve.Large eddy simulation and measurements of tur-bulent enclosed rotor-stator flows. Phys. Fluids,19:085113, 2007.[15] E. Se´verac, and E. Serre. A Spectral Viscos-ity LES model for the simulation of turbulentflows within rotating cavities. J. Comp. Phys.,226(6):1234–1255, 2007.4

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France South Pilot Centre - Main activities of the MSNM-GP laboratory

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