Reynolds Stress Closure in Hybrid RANS-LES Methods

Abstract

The feasibility of using the elliptic blending Reynolds stress model (EB-RSM) in hybrid RANS-LES methods is investigated in this paper. The advantage of the EB-RSM is that it does not use any geometrical wall distance or wall normal vector information which makes it well suited for application in flows with complex wall geometries. A slight modification to the original EB-RSM is proposed to improve the performance for flows with separation. The model is also extended to a sub-grid scale model for fully resolved LES and several possibilities for use as a hybrid RANS-LES model are presented. The RANS EB-RSM model performed overall well in plane channel flows, the periodic hill flow and the flow over a NACA 4412 airfoil with trailing edge separation. In LES, the EB-RSM model provided very good results in a plane channel flow at low Reynolds number. When used as a zonal hybrid RANS-LES model, the EB-RSM displayed a significant log-layer mismatch although the relevance of the modeled and resolved stresses switched right at the prescribed interface.