Wall - layer models for LES of separated flows

In order to extend large-eddy simulation (LES) to practical engineering and aeronautical applications, wall-layer model are required. In the present study recent developments in this field are presented. A new version of the two-layer model (TLM) is proposed and tested in a separated flow. The TLM methodology is based on a zonal approach, in which the computational domain is divided in an outer-flow region, where the filtered Navier-Stokes equation are solved and an inner-layer, near the solid walls. In this layer a simplified set of equations is solved and the effect of all turbulent structures is modeled. A limit of the TLM formulation, as used so far, is that an algebraic turbulence model is used to parameterize the effect of turbulence in the inner-layer. Although, the results in equilibrium flows were very satisfactory, some loss of accuracy is expected in separated flows. To account for the more complex physics in this type of flows a more advanced turbulent model, namely the Spalart-Allmaras model [Rech. Aérospatiale 1, 5–21, (1994)] is introduced. The results obtained for the backward-facing-step flow agree well with the reference data.