Using a Stochastic Backscatter Model for Wall-Modelled Large Eddy Simulation

Abstract

This paper investigates the possibility to extend a hybrid RANS--LES method that employs a stochastic backscatter model to Wall-Modelled LES. The coefficients of the model have been optimized to minimize the log-layer mismatch for channel flow, while maintaining the proper decay rate for isotropic turbulence. Application to the co-flow of a wake and a boundary layer shows that the backscatter model ensures the rapid development of resolved turbulence in stream-wise direction after switching from RANS to LES, both in attached and separated shear layers, without adding synthetic turbulence. An alternative formulation of the backscatter model is also considered that ensures a zero mean value of the stochastic forcing. Results are shown for channel flow and for the co-flow.