DES and Hybrid RANS/LES models for unsteady seperated turbulent flow predictions

Abstract

This paper proposes two DES (Detached Eddy Simulation) model and one hybrid RANS (Reynolds Averaged Navier -Stokes)/ LES (Large Eddy Simulation) model for the simulations of unsteady separated turbulent f lows. The two -equation k -� based models are implemented in a full 3 -D Navier Stokes solver and simulations are carried out using a 3 rd order Roe scheme. The predictions of the models are compared for a benchmark problem involving transonic flow over an ope n cavity and the equivalence between the DES formulations and the hybrid formulation is established. Predicted results for the vorticity, pressure fluctuations, SPL (Sound Pressure level) spectra and different turbulent quantities; such as modeled and reso lved TKE (Turbulent Kinetic Energy) profiles, contours and spectra are presented to evaluate various aspects of the proposed models. The numerical results for the SPL spectra are compared with available experimental results and also with the prediction fro m LES simulations. The grid resolved TKE profiles are also compared with the LES predictions. A comparative study of the CPU time required for the two DES models and the hybrid model is also made.