Coupling of solvers with non-conforming computational domains in a dual-mesh hybrid LES/RANS framework

Abstract

In a recently proposed dual-mesh hybrid framework (Xiao and Jenny, J. Comput. Phys. 231 (4) (2012)), LES and RANS simulations are conducted simultaneously on the same domain, but on different meshes. In the current work, this framework is further extended to allow for non-conforming computational domains for the LES and the RANS simulations. With this extension we developed a hybrid solver coupling a high-order LES code based on Cartesian meshes with a general-purpose RANS solver based on body-fitting meshes. A relaxation approach is used to enforce the solid boundary conditions in the LES. Plane channel flow at Reτ=590 and flows over periodic hills at two Reynolds numbers (Re=2800 and 10,595) are investigated with the new solver. The adequacy of the boundary representation and forcing strategy is shown. The numerical studies also demonstrate the flexibility of the extended solver and the predictive capability of the new hybrid framework, which consists of two solvers operating on the same physical domain, but with non-conforming computational domains (i.e., a Cartesian mesh based LES solver combined with a body-fitting mesh based RANS solver). The extensions explored in this study are of practical importance for industrial CFD applications as they successfully demonstrate how academic, very accurate, massively parallel LES solvers can be coupled with flexible RANS solvers. Since the coupling strategy is minimally intrusive, it is attractive for industrial purposes. With the current framework, the potential of many existing academic codes for practical flow simulations, where complex geometries and wall resolution requirements represent major hurdles, can be explored.