SDevelopment of a Two-way Coupled Hybrid RANS-LES Scheme for Numerical Simulation of Turbulent Fluid Flows

Abstract

Large-eddy simulation (LES) and Reynolds Averaged Navier Stokes (RANS) are both widely used for numerically simulating wall-bounded turbulent flows at high Reynolds numbers. Wall-resolved Large-eddy simulations (LES), while being accurate, requires high grid resolution near the wall, while Reynolds-averaged Navier-Stokes (RANS) simulations, while being computationally inexpensive, can be inaccurate outside the turbulent boundary layer. To mitigate these issues, we develop a Coupled RANS-LES (CRL) approach, and implement the formulation in an in-house solver. Here, governing equations for both RANS and LES are solved in the entire flow domain. The subgrid stress is constrained to be consistent with RANS (Spalart-Allmaras model) near the wall, and with LES (Smagorinsky model) away from the wall. Moreover, a novel two-way coupling is introduced between the RANS and LES equations. We compare results from our CRL with Detached Eddy Simulations (DES) and we find that the CRL performs better than the DES in terms of predicting the mean velocity profile as well.