# CerfacsEntrez dans le monde de la haute performance...

### Le Cerfacs en bref

Centre de recherche fondamentale et appliquée spécialisé dans la modélisation et la simulation numériques, également centre de formation avancée, le Cerfacs, par ses moyens et son savoir-faire en calcul haute performance, traite des grands problèmes scientifiques et techniques de recherche publique et industrielle sur les secteurs suivants: AERONAUTIQUE&AUTOMOBILEESPACEENERGIEENVIRONNEMENT&CLIMAT
Ses effectifs sont de l'ordre de 100-150 chercheurs, ingénieurs et administratifs.

## Contribution du CECI au « Petit Illustré » sur les Systèmes complexes (édition CNRS)

12 octobre 2017

Le CECI (Cerfacs, CNRS) et L'IMFT travaillent à la modélisation numérique des processus à l'origine des crues de rivières et de leurs incertitudes. Une contribution commune sur ce sujet, signée de Sophie Ricci et Hélène Roux, est publiée dans le numéro 34 de la collection "Petit...Lire la suite

## Le Cerfacs était présent à la Nuit Européenne des Chercheur.e.s 2017 à Toulouse

1 octobre 2017

"Peut-on faire entrer un moteur, un avion ou la Terre entière dans un ordinateur ?". Tel était le titre accrocheur du stand du Cerfacs vendredi 29 septembre pour la Nuit Européennes des Chercheur.e.s dont le thème était "Impossible". Une centaine de personnes, au Quai des Savoirs à Toulouse,...Lire la suite

### L'AGENDA

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### NOS PUBLICATIONS

Mejia, D., Brebion, M., Ghani, A., Kaiser, E., Duchaine, F., Selle, L. and Poinsot, T. (2017) Influence of flame-holder temperature on the acoustic flame transfer functions of a laminar flame, Combustion and Flame, 188, pp. 5-12, doi:10.1016/j.combustflame.2017.09.016
@ARTICLE{AR-CFD-17-194, author = {Mejia, D. and Brebion, M. and Ghani, A. and Kaiser, E. and Duchaine, F. and Selle, L. and Poinsot, T. }, title = {Influence of flame-holder temperature on the acoustic flame transfer functions of a laminar flame}, year = {2017}, volume = {188}, pages = {5-12}, doi = {10.1016/j.combustflame.2017.09.016}, journal = {Combustion and Flame}, abstract = {The occurrence of combustion instabilities in high-performance engines such as gas turbines is often affected by the thermal state of the engine. For example, strong bursts of pressure fluctuations may occur at cold start for operating conditions that are stable once the engine reaches thermal equilibrium. This observation raises the question of the influence of material temperature on the response of flames to acoustic perturbations. In this study, we assess the influence of the temperature of the flame holder for a laminar flame. Both experiments and numerical simulations show that the Flame Transfer Function (FTF) is strongly affected by the flame-holder temperature. The key factors driving the evolution of the FTF are the flame-root location as well as the modification of the flow, which affects its stability. In the case of the cooled flame-holder, the formation of a recirculation zone is identified as the main impact on the FTF.}}

Berger, S., Duchaine, F. and Gicquel, L. Y. M. (2017) Bluff-body Thermal Property and Initial State Effects on a Laminar Premixed Flame Anchoring Pattern, Flow Turbulence and Combustion, ISSN 1573-1987, doi:10.1007/s10494-017-9841-y
@ARTICLE{AR-CFD-17-195, author = {Berger, S. and Duchaine, F. and Gicquel, L.Y.M. }, title = {Bluff-body Thermal Property and Initial State Effects on a Laminar Premixed Flame Anchoring Pattern}, year = {2017}, issn = {1573-1987}, doi = {10.1007/s10494-017-9841-y}, journal = {Flow Turbulence and Combustion}, abstract = {Bluff-body stabilized laminar flames remain at the root of many industrial applications. Such a simple flame arrangement although steady results from complex chemical, flow mixing as well as solid body thermal interactions that are still today misunderstood. Numerically, accurate predictions of such non linear problems require Conjugate Heat Transfer (CHT) approaches that are seldom because of the need for complex fluid flow solvers as well as multi-physics coupling strategies that are computationally expensive and difficult to master. Such numerical tools however provide access to fundamental elements otherwise inaccessible. Relying on Direct Numerical Simulation (DNS) CHT based predictions, the following work underlines several key features of importance to predict and understand square bluff-body stabilized flames. In the case of fluid only predictions, where the bluff-body wall temperature is fixed and assumed constant, three possible flame topologies are obtained and respectively qualified as anchored, lifted and bowed flames. Out of these three stable flow solutions, only two topologies are found physically possible whenever computed in a CHT context. Furthermore, depending on the solid material and the initial solution, the non linear CHT problem exhibits multiple solutions highlighting the complex coupling that can arise. As evidenced by these simple flame problems, such a behavior higlights the potential difficulties of predicting flame wall interaction problems where coupling schemes and turbulent closures / modeling will be required.}, keywords = {LES, Heat transfer, Reacting flow, CHT, Coupling scheme and Convergence }}

Sanchez-Gomez, E., Cassou, C., Ruprich-Robert, Y., Fernandez, E. and Terray, L. (2017) Drift dynamics in a coupled model initialized for decadal forecasts, Climate Dynamics, 46 (5), pp. 1819-1840, doi:10.1007/s00382-015-2678-y
@ARTICLE{AR-CMGC-17-175, author = {Sanchez-Gomez, E. and Cassou, C. and Ruprich-Robert, Y. and Fernandez, E. and Terray, L. }, title = {Drift dynamics in a coupled model initialized for decadal forecasts}, year = {2017}, number = {5}, volume = {46}, pages = {1819-1840}, doi = {10.1007/s00382-015-2678-y}, journal = {Climate Dynamics}, pdf = {http://cerfacs.fr/wp-content/uploads/2016/04/GLOBC-2015-Article-Sanchez_et_al_CLIMDYN.pdf}, url = {http://link.springer.com/article/10.1007%2Fs00382-015-2678-y}}

Daroukh, M., Moreau, S., Gourdain, N., Boussuge, J. -F. and Sensiau, C. (2017) Effect of Distortion on Turbofan Tonal Noise at Cutback with Hybrid Methods, International Journal of Turbomachinery, Propulsion and Power, 2 (3), pp. 16, doi:10.3390/ijtpp2030016
@ARTICLE{AR-CFD-17-155, author = {Daroukh, M. and Moreau, S. and Gourdain, N. and Boussuge, J.-F. and Sensiau, C. }, title = {Effect of Distortion on Turbofan Tonal Noise at Cutback with Hybrid Methods}, year = {2017}, number = {3}, volume = {2}, pages = {16}, doi = {10.3390/ijtpp2030016}, journal = {International Journal of Turbomachinery, Propulsion and Power}, abstract = { New ultra high bypass ratio architectures may significantly affect the fan tonal noise of future aircraft engines. Indeed, such a noise source is supposed to be dominated by the interaction of fan-blade wakes with outlet guide vanes. However, shorter nacelles in these engines are expected to trigger an important air-inlet distortion that can be responsible for new acoustic sources on the fan blades. Full annulus simulations based on the unsteady Reynolds-averaged Navier–Stokes equations are presently used to study this effect. Simulation results show that the air-inlet distortion has a main effect in the fan-tip region, leading to a strong variation of the fan-blade unsteady loading. It also significantly modifies the shape of the fan-blade wakes and, consequently, the unsteady loading of the outlet guide vanes. Acoustic predictions based on the extension of Goldstein’s analogy to an annular duct in a uniform axial flow are presented and show that the fan sources notably contribute to the fan tonal noise. The air-inlet distortion is responsible for an increase of the noise radiated by both the fan and the outlet guide vane sources, leading to a global noise penalty of up to three decibels.}, keywords = {AAM, ELSA}, pdf = {http://cerfacs.fr/wp-content/uploads/2017/09/Daroukh_IJTPP_2017.pdf}}

Coreixas, C., Wissocq, G., Puigt, G., Boussuge, J. -F. and Sagaut, P. (2017) Recursive regularization step for high-order lattice Boltzmann methods, Physical Review E, 96 (3), pp. 033306 (1-22), doi:10.1103/PhysRevE.96.033306
@ARTICLE{AR-CFD-17-140, author = {Coreixas, C. and Wissocq, G. and Puigt, G. and Boussuge, J.-F. and Sagaut, P. }, title = {Recursive regularization step for high-order lattice Boltzmann methods}, year = {2017}, number = {3}, volume = {96}, pages = {033306 (1-22)}, doi = {10.1103/PhysRevE.96.033306}, journal = {Physical Review E}, abstract = {A lattice Boltzmann method (LBM) with enhanced stability and accuracy is presented for various Hermite tensor-based lattice structures. The collision operator relies on a regularization step, which is here improved through a recursive computation of non-equilibrium Hermite polynomial coefficients. In addition to the reduced computational cost of this procedure with respect to the standard one, the recursive step allows to considerably enhance the stability and accuracy of the numerical scheme by properly filtering out second- (and higher-) order non-hydrodynamic contributions in under-resolved conditions. This is first shown in the isothermal case where the simulation of the doubly periodic shear layer is performed with a Reynolds number ranging from $10^4$ to $10^6$, and where a thorough analysis of the case at $Re=3\times 10^4$ is conducted. In the latter, results obtained using both regularization steps are compared against the BGK-LBM for standard (D2Q9) and high-order (D2V17 and D2V37) lattice structures, confirming the tremendous increase of stability range of the proposed approach. Further comparisons on thermal and fully compressible flows, using the general extension of this procedure, are then conducted through the numerical simulation of Sod shock tubes with the D2V37 lattice. They confirm the stability increase induced by the recursive approach as compared with the standard one. }}

### DOMAINES D'APPLICATION

Environnement et climatEspaceÉnergieAéronautique & Automobile

## Analyse et réduction de la cinétique chimique de la combustion

Contexte : la pénurie attendue de combustibles fossiles conduit l'industrie aéronautique à envisager l'ajout de combustibles de remplacement dans...Lire plus

## Stage : Découverte du calcul quantique

Contexte : Le Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS) travaille à la résolution, par la...Lire plus