EFFECT OF LES LENGTH SCALE AND NUMERICAL SCHEME IN HYBRID RANS-LES OF FREE SHEAR LAYER FLOWS

Paper i proceeding, 2022

The effect of LES length scales, treatment of near-wall functions in the LES domain and numerical discretization schemes has been evaluated in SA-DDES simulations of free shear layer flows. In a fundamental low Mach number free shear layer flow it has been shown that the choice of LES length scale, how the near-wall functions are treated in LES mode and the numerical scheme is of vital importance for an accurate prediction of the mixing and the resolved turbulent Reynolds stresses. In simulations of a transonic flow over the generic M219 cavity it was observed that the choice of LES length scale is not as evident as in the fundamental free shear layer. However, it was clear that vorticity based LES length scales improve the prediction of the overall sound pressure levels, the Rossiter modes and the mean flow field compared to Δmax used in the original formulation of SA-DDES.