Numerical experiments with slip wall boundary conditions in large-eddy simulation

Traditional wall models for large-eddy simulation (LES) use Reynolds-averaged closure models to provide wall-stress boundary conditions to the LES equations. The slip wall boundary condition is derived directly from the LES constitutive equations, and allows for the development of dynamic wall models free from RANS phenomenological modeling (Bose & Moin, PoF, 2014). Recent wall-modeled LES calculations with slip wall boundary conditions have reported sensitivity to mesh resolution, subgrid-scale model, and numerical discretization (Bae et al., JFM, 2019).

In this study numerical experiments are performed with slip wall models in high-Reynolds number channels and flow over a Gaussian bump with separation (Williams et al., 2020). We investigate effects of mesh resolution, transpiration control, and subgrid-scale model wall closure. The RANS-based equilibrium wall model provides reasonable predictions of separation at coarser resolutions, but fails to separate at finer resolutions until a wall-resolved LES limit is reached. In contrast, the slip boundary condition is shown to predict the separation across the mesh resolutions considered.