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Cerfacs in brief

Centre of basic and applied research specialized in modelling and numerical simulation, Cerfacs, through its facilities and expertise in high-performance computing, deals with major scientific and technical research problems of public and industrial interest.

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NEWS

New regional climate projections for metropolitan France

superadmin |  11 February 2021

Cerfacs collaborated with Météo France and the Institut Pierre-Simon-Laplace (IPSL) to produce the DRIAS climate dataset, which presents a wide range of possible climate changes for metropolitan France for three periods of the 21st century (2021-2050, 2041-2070 and 2071-2100) and three greenhouse gas emission scenarios. Liens : .pdfRead more


New research group “Theory and Climate”

Mélanie ROCHOUX |  1 February 2021

CECI is involved in the development of a new research group (GDR for “Groupement De Recherche”) entitled “Theory and Climate”. This GDR aims at bringing together the entire community of theorists (mathematicians, physicists, computer scientists, data scientists, etc.) working on climate sciences, with the goal of developing and sharing innovative concepts and tools relevant for a better understanding of climate dynamics. This GDR is interdisciplinary and involves several CNRS research institutes as well as most of French organizations working in these fields. CECI plans to contribute to issues related to climate dynamics and applied mathematics such as data assimilation and machine learning. Moreover, there are strong links between this GDR and the LEFE-INSU actions, in which CECI researchers are active (LEFE-IMAGO and LEFE-MANU actions). More information here:Read more

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RESEARCH PUBLICATIONS

Qasmi, S., Sanchez-Gomez, E., Ruprich-Robert, Y., Boé, J. and Cassou, C. (2021) Modulation of the Occurrence of Heatwaves over the Euro-Mediterranean Region by the Intensity of the Atlantic Multidecadal Variability, Journal of Climate, 34 (3), pp. 1099–1114, doi:10.1175/JCLI-D-19-0982.1

[pdf] [doi]

@ARTICLE{AR-CMGC-21-21, author = {Qasmi, S. and Sanchez-Gomez, E. and Ruprich-Robert, Y. and Boé, J. and Cassou, C. }, title = {Modulation of the Occurrence of Heatwaves over the Euro-Mediterranean Region by the Intensity of the Atlantic Multidecadal Variability}, year = {2021}, number = {3}, volume = {34}, pages = {1099–1114}, doi = {10.1175/JCLI-D-19-0982.1}, journal = {Journal of Climate}, pdf = {https://cerfacs.fr/wp-content/uploads/2021/01/GlobC-Article-Qasmi-Modulation-of-the-Occurrence-of-Heatwaves-over-the-Euro-Mediterranean-Region-by-the-Intensity-of-the.pdf}}

Cai, S-G., Degrigny, J., Boussuge, J. -F. and Sagaut, P. (2021) Coupling of turbulence wall models and immersed boundaries on Cartesian grids, Journal of Computational Physics, 429 (March), pp. 109995, doi:10.1016/j.jcp.2020.109995

[url] [doi]

@ARTICLE{AR-CFD-21-30, author = {Cai, S-G. and Degrigny, J. and Boussuge, J.-F. and Sagaut, P. }, title = {Coupling of turbulence wall models and immersed boundaries on Cartesian grids}, year = {2021}, number = {March}, volume = {429}, pages = {109995}, doi = {10.1016/j.jcp.2020.109995}, journal = {Journal of Computational Physics}, abstract = {An improved coupling of immersed boundary method and turbulence wall models on Cartesian grids is proposed, for producing smooth wall surface pressure and skin friction at high Reynolds numbers. Spurious oscillations are frequently observed on these quantities with most immersed boundary wall modeling methods, especially for the skin friction which is found to be very sensitive to the solid surface's position and orientation against the Cartesian grids. The problem originates from the irregularity of the wall distance on the stair-step grid boundaries where the immersed boundary conditions are applied. To reduce this directional error, several modifications are presented to enhance the near wall solution. First, the commonly used interpolation for the flow velocity is replaced by one for the friction velocity, which has much less variation near wall. The concept of using a fictitious point to retrieve flow fields in the wall normal direction is abandoned and the interpolatio n is performed in the wall parallel plane with existing fluid points. Secondly, the velocity gradients at the approximated boundary are computed with advanced schemes and the normal gradient of the tangential velocity is reconstructed from the wall laws. To further protect the near wall solution, the normal velocity gradient and the working viscosity from the Spalart-Allmaras turbulence model are enforced by their theoretical solutions in the interior fluid close to the wall. Additionally, various post-processing algorithms for reconstructing wall surface quantities and force integrations are investigated. Other related factors are also discussed for their effects on the results. The validity of present method has been demonstrated through numerical benchmark tests on a flat plate at zero pressure gradient, both aligned and inclined with respect to the grid, as well as aerodynamic cases of NACA 23012 airfoil and NASA trap wing.}, keywords = {Immersed boundary method, Wall model, High Reynolds number, Reynolds-averaged Navier–Stokes equations}, url = {https://www.sciencedirect.com/science/article/pii/S0021999120307695?via%3Dihub}}

Mirouze, I. and Ricci, S. (2021) Smurf: System for Modelling with Uncertainty Reduction, and Forecasting, Journal of Open Research Software, 9 (1), doi:10.5334/jors.312

[pdf] [doi]

@ARTICLE{AR-CMGC-21-31, author = {Mirouze, I. and Ricci, S. }, title = {Smurf: System for Modelling with Uncertainty Reduction, and Forecasting}, year = {2021}, number = {1}, volume = {9}, doi = {10.5334/jors.312}, journal = {Journal of Open Research Software}, pdf = {https://cerfacs.fr/wp-content/uploads/2021/02/GlobC-Article-Mirouze-Smurf-JORS-2021.pdf}}

Muscat, L., Puigt, G., Montagnac, M. and Brenner, P. (2021) Mathematical analysis of the spatial coupling of an explicit temporal adaptive integration scheme with an implicit time integration scheme, International Journal for Numerical Methods in Fluids, 93 (3), pp. 774-815, doi:10.1002/fld.4908

[url] [doi]

@ARTICLE{AR-CFD-21-32, author = {Muscat, L. and Puigt, G. and Montagnac, M. and Brenner, P. }, title = {Mathematical analysis of the spatial coupling of an explicit temporal adaptive integration scheme with an implicit time integration scheme}, year = {2021}, number = {3}, volume = {93}, pages = {774-815}, doi = {10.1002/fld.4908}, journal = {International Journal for Numerical Methods in Fluids}, abstract = {The Reynolds‐averaged Navier–Stokes equations and the large eddy simulation equations can be coupled using a transition function to switch from a set of equations applied in some areas of a domain to the other set in the other part of the domain. Following this idea, different time integration schemes can be coupled. In this context, we developed a hybrid time integration scheme that spatially couples the explicit scheme of Heun and Crank–Nicolson's implicit scheme using a dedicated transition function. This scheme is linearly stable and second‐order accurate. In this article, an extension of this hybrid scheme is introduced to deal with a temporal adaptive procedure. The idea is to treat the time integration procedure with unstructured grids as it is performed with Cartesian grids and local mesh refinement. Depending on its characteristic size, each mesh cell is assigned to a rank. And for two cells from two consecutive ranks, the ratio of the associated time steps for time marching the solutions is 2. As a consequence, the cells with the lowest rank iterate more than the other ones to reach the same physical time. In a finite‐volume context, a key ingredient is to keep the conservation property for the interfaces that separate two cells of different ranks. After introducing the different schemes, the article recalls briefly the coupling procedure, and details the extension to the temporal adaptive procedure. The new time integrator is validated with the propagation of 1D wave packet, the Sod's tube, and the advection of 2D vortex.}, keywords = { compressible unsteady flows, finite volume formulation, hybrid time integration, local time stepping, space–time stability analysis}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/fld.4908}}

Shastry, V., Cazères, Q., Rochette, B., Riber, E. and Cuenot, B. (2021) Numerical study of multicomponent spray flame propagation, Proceedings of the Combustion Institute, 38, doi:10.1016/j.proci.2020.07.090

[url] [doi]

@ARTICLE{AR-CFD-21-6, author = {Shastry, V. and Cazères, Q. and Rochette, B. and Riber, E. and Cuenot, B. }, title = {Numerical study of multicomponent spray flame propagation}, year = {2021}, volume = {38}, doi = {10.1016/j.proci.2020.07.090}, journal = {Proceedings of the Combustion Institute}, abstract = {A computational study of one dimensional multicomponent laminar Jet-A/air spray flames is presented. The objective is to understand the effect of various spray parameters (diameter, droplet velocity, liquid loading) on the spray flame structure and propagation. Simulation of the Eulerian gas phase is coupled with a Lagrangian tracking of the dispersed liquid phase. Jet-A surrogate of n-dodecane, methyl-cyclohexane and xylene is considered. A discrete multicomponent model for spray vaporization is used along with an analytically reduced chemistry for computing the gas phase reactions. Both overall lean and rich cases are examined and compared with existing literature for single component spray flames. The preferential evaporation effect, unique to multicomponent fuels causes a variation of fuel vapor composition on both sides of the flame front and this has a direct impact on the spray flame structure and propagation speed. In the rich cases, multiple flame structures exist due to the staged release of vapors across the reactive zone. Spray flame speed correlations proposed for single component fuels are extended to the multicomponent case, for both zero and high relative velocity between the liquid and the gas. The correlations are able to accurately predict the effective equivalence ratio at which the flame burns and hence the laminar spray flame speeds of multicomponent fuels for all cases studied in this work.}, keywords = {Laminar spray flame, Multicomponent evaporation, Analytically reduced chemistry, Preferential evaporation, Flame structure}, url = {https://www.sciencedirect.com/science/article/abs/pii/S154074892030540X}}

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Developer: scientific workflows and interfaces to support climate data

 

Description The work will focus on several aspects that require collaborative and agile design and development....Read more


Réduction de la dimension des champs des variables hydrologiques pour une méta-modélisation robuste et fiable dans le contexte de la prévision des crues et des inondations.

 

Contacts :   Sophie Ricci (Cerfacs, Toulouse), ricci@cerfacs.fr Siham El Garroussi (Cerfacs, Toulouse), garroussi@cerfacs.fr Pour candidater,...Read more

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