CELTIC
(2022-2025)
Continuous Embedded LES for Turbulent flows in Industrial Configurations
Call ESR 2022 of the New-Aquitaine Region
Coordinator : Rémi Manceau
Partner : GDTech
For the numerical simulation of turbulent fluid flows (CFD), which is of great importance in many industrial and environmental applications, hybrid RANS/LES methods are based on a multi-scale type of resolution, either in zones separated by an interface (zonal method) or by a progressive shift in the scale of description (continuous method), which allows to drastically decrease the computational cost of unsteady simulations (LES), while maintaining a fineness of description of the physics in the regions where it is necessary. A particularly attractive approach is the Embedded LES method which consists in reserving the LES to a small area included in a global RANS domain, which is a particular strategy for using the zonal hybrid RANS/LES. However, the zonal approach is characterized by a predetermined partition between the RANS and LES zones and a discontinuous interface, which prohibits any evolution of the scale of description of turbulence during the computation, which would allow an adaptivity of the model according to physical criteria determined during the calculation.
The first objective of the project is therefore to develop embedded LES in the context of continuous approaches (CELES, Continuous Embedded LES), in which the interface between RANS and LES is now a diffuse interface. In these approaches, the domain is not split into sub-domains, but the model evolves in a continuous manner so that it tends towards a RANS model or towards a LES model. The diffuse interface (grey area) is this transition area in which one goes from a RANS model to a LES model. It will then be necessary, as in the zonal approach, to enrich the RANS solution by adding synthetic turbulence to avoid the drastic decrease of the total turbulent stress at the beginning of the LES zone which would strongly degrade the results. In the framework of the hybrid RANS/LES approach developed at LMAP by the Inria CAGIRE project-team, an approach called HTLES (Hybrid Temporal LES), this aspect of the project consists in developing a volume enrichment approach based on a fluctuating force.
Although some industrial groups develop their own computational code, including the open-source code Code_Saturne from EDF that we use in our research, a majority of industrial simulations are done with commercial codes. The second objective of the project is therefore to implement our HTLES method and the new CELES method in a commercial code, in order to demonstrate the applicability of the method in such a code. A series of test cases of increasing complexity, chosen for their relevance to industrial problems, will allow both to perform a cross validation between the research code and the commercial code, and to serve as a demonstrator of the applicability of the method in industrial configurations.
