Cerfacs Enter the world of high performance ...

@ARTICLE{AR-CFD-19-123, author = {Le Bras, S. and Deniau, H. and Bogey, C. }, title = {A technique of flux reconstruction at the interfaces of non-conforming grids for aeroacoustic simulations}, year = {2019}, number = {12}, volume = {91}, pages = {587-614}, doi = {10.1002/fld.4767}, journal = {International Journal for Numerical Methods in Fluids}, abstract = {A flux reconstruction technique is presented in order to perform aeroacoustic computations using implicit high-order spatial schemes on multiblock structured grids with non-conforming interfaces. The use of such grids, with mesh spacing discontinuities across the block interfaces, eases local mesh refinements, simplifies the mesh generation process, and thus facilitates the computation of turbulent flows. In this work, the spatial discretization consists of sixth-order finite-volume implicit schemes with low-dispersion and lowdissipation properties. The flux reconstruction is based on the combination of non-centered schemes with local interpolations to define ghost cells and compute flux values at the grid interfaces. The flow variables in the ghost cells are calculated from the flow field in the grid cells using a meshless interpolation with radial basis functions. In this study, the flux reconstruction is applied to both plane and curved non-conforming interfaces. The performance of the method is first evaluated by performing two-dimensional simulations of the propagation of an acoustic pulse and of the convection of a vortex on Cartesian and wavy grids. No significant spurious noise is produced at the grid interfaces. The applicability of the flux reconstruction to a 3-D computation is then demonstrated by simulating a jet at a Mach number of 0.9 and a diameter-based Reynolds number of 4× 105 on a Cartesian grid. The non-conforming grid interface located downstream of the jet potential core does not appreciably affect the flow development and the jet sound field, while reducing the number of mesh points by a factor of approximately two. }, keywords = {AEROACOUSTICS, FINITE VOLUMES, HIGH-ORDER SCHEMES, MESHLESS INTERPOLATION, NONCONFORMING GRIDS, STRUCTURED GRIDS}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/fld.4767}}

@ARTICLE{AR-CFD-19-156, author = {Harnieh, M. and Thomas, M. and Bizzari, R. and Dombard, J. and Duchaine, F. and Gicquel, L.Y.M. }, title = {Assessment of a coolant injection model on cooled high-pressure vanes with Large-Eddy Simulation}, year = {2019}, volume = {online}, doi = {10.1007/s10494-019-00091-3}, journal = {Flow Turbulence and Combustion}, abstract = {The high-pressure turbine blades are the components of the aero-engines which are the most exposed to extreme thermal conditions. To alleviate this issue, the blades are equipped with cooling systems to ensure long-term operation. However, the accurate prediction of the blade temperature and the design of the cooling system in an industrial context still remains a major challenge. Potential improvement is foreseen with Large-Eddy Simulation (LES) which is well suited to predict turbulent flows in such complex systems. Nonetheless, performing LES of a real cooled high-pressure turbine still remains expensive. To alleviate the issues of CPU cost, a cooling model recently developed in the context of combustion chamber liners is assessed in the context of blade cooling. This model was initially designed to mimic coolant jets injected at the wall surface and does not require to mesh the cooling pipes leading to a significant reduction in the CPU cost. The applicability of the mod el is here evaluated on the cooled Nozzle Guide Vanes (NGV) of the Full Aerothermal Combustor Turbine interactiOns Research (FACTOR) test rig. To do so, a hole modeled LES using the cooling model is compared to a hole meshed LES. Results show that both simulations yield very similar results confirming the capability of the approach to predict the adiabatic film effectiveness. Advanced post-processing and analyses of the coolant mass fraction profiles show that the turbulent mixing between the coolant and hot flows is however reduced with the model. This finding is confirmed by the turbulent map levels which are lower in the modeled approach. Potential improvements are hence proposed to increase the accuracy of such methods.}, keywords = {Large-eddy simulation, Turbomachinery, Film cooling, Modelling}}

@ARTICLE{AR-CMGC-19-170, author = {Rahaman, H. and Srinavisu, U. and Panickal, S. and Durgadoo, J.V. and Griffies, S.M. and Ravichandran, M. and Bozec, A. and Cherchi, A. and Voldoire, A. and Sidorenko, D. and Chassignet, E.P. and Danabasoglu, G. and Tsujino, H. and Getzlaff, K. and Ilicak, M. and Bentsen, M. and Long, M.C. and Fogli, P.G. and Danilov, S. and Marsland, S.J. and Valcke, S. and Yeager, S.G. and Wang, Q. }, title = {An assessment of the Indian Ocean mean state and seasonal cycle in a suite of interannual CORE-II simulations}, year = {2019}, volume = {145}, pages = {1-45}, doi = {10.1016/j.ocemod.2019.101503 }, journal = {Ocean Modelling}, pdf = {https://cerfacs.fr/wp-content/uploads/2019/11/GlobC-Article-Valcke-Ocenamodelling.pdf}}

@ARTICLE{AR-CMGC-19-178, author = {Cassou, C. and Drouard, M. }, title = {A Modeling- and Process-Oriented Study to Investigate the Projected Change of ENSO-Forced Wintertime Teleconnectivity in a Warmer World}, year = {2019}, number = {8047-8068}, volume = {32}, doi = {10.1175/JCLI-D-18-0803.1 }, journal = {Journal of Climate}, pdf = {https://cerfacs.fr/wp-content/uploads/2019/11/GlobC-Article-drouard_cassou_jclim.pdf}}

@ARTICLE{AR-CFD-19-182, author = {Queguineur, M. and Bridel-Bertomeu, T. and Gicquel, L.Y.M. and Staffelbach, G. }, title = {Large eddy simulations and global stability analyses of an annular and cylindrical rotor/stator cavity limit cycles}, year = {2019}, number = {10}, volume = {31}, pages = {paper 104109}, doi = {10.1063/1.5117335}, journal = {Physics of Fluids}, abstract = {Although rotating cavity flows are essential components of industrial applications, their dynamics is still largely misunderstood. From computer hard-drives to turbopumps of space launchers, designed devices often produce flow oscillations that can destroy the component prematurely, or produce disturbing noise or undesired operating modes of the system. The fundamentals of encountered static and rotating flow boundary layers have evidenced, a long time ago now, the presence of specific boundary layer instabilities and structures for low Reynolds numbers. For higher Reynolds numbers and fully enclosed systems, features are, however, more complex with the apparition of multifrequency oscillations populating the entire cavity limit cycle. For these flows, Large Eddy Simulation (LES) has illustrated the capacity of reproducing features and limit cycles. However, identifying the origin and region within these flows that are responsible for mode selections remains difficult if not impossible using such computational fluid dynamics tools. The present contribution evaluates a LES and a global stability analysis framework to identify the mechanisms responsible for the observed limit-cycles of two types of rotor-stator cavities. In particular, the presence of a central body or shaft and its impact on the instability selection is of interest here, i.e., the identification of the regions of mode activation for a cylindrical as well as an annular cavity is detailed. Results issued by the conjunct use of dynamical mode decomposition and Global Linear Stability Analysis (GLSA) confirm the observed LES dynamics. Most importantly, GLSA gives access to the triggering mechanisms at the root of the limit-cycles expression as well as hints on the mode selection. In that respect, a cylindrical cavity is shown to sustain more complex features than an annular cavity because of an enhanced flow curvature near the central shaft.}, keywords = {Turbulence simulations, Linear stability analysis, Boundary layer flow, Computational fluid dynamics}}