PARAMETRIC STUDY ON THE BLENDING FUNCTION IN TRANSITION ZONE OF THE LES/RANS METHOD

Two-equation k-ω SST turbulence model was combined with Sagaut's mixed-length subgrid-scale model with a blending function to construct a hybrid large-eddy/Reynolds-averaged Navier-Stokes method. The method was used to compute a plate turbulent boundary layer at Mach number 2.8 with fifth-order WENO scheme. A recycling/rescaling method was used to generate and sustain turbulent fluctuations at the inlet. The RANS to LES transition parameters and mesh resolution were considered in order to assess the method. The results showed that the hybrid method could capture the large-scale structure in the turbulent boundary-layer and no shift of the inlet mean parameters was observed. The blending function should be designed to transition to LES toward the outer part of the logarithmic region and the transition should be sharp to obtain the correct Reynolds shear stress. Single point-second order velocity fluctuations statistics might be obtained and accepted on streamwise and spanwise meshes scaled by Escudier mixing length.