Simulations of Separated Flow around an Airfoil with Ice Shape using Hybrid RANS/LES Models

Abstract

Accurate prediction of high Reynolds number flow fields around complex geometries requires turbulence models that have favorable characteristics with regard to numerical stability, computational cost, mesh sensitivity, and accuracy. In order to investigate the feasibility of a new Hybrid RANS/LES (HRL) model with respect to these characteristics, numerical simulations were performed over a rearward facing step at ReH = 37,000 and around a GLC-305 airfoil configured with a 22.5-minute glaze ice accretion at Re = 3.5x10 6 , M = 0.12, and α = 6°. In the case of rearward facing step flow, comparisons were made between simulation results that employed a RANS model (Shear Stress Transport (SST)), the Delayed Detached Eddy Simulation (DDES) model, and the new HRL model. Mean velocity profiles of the new HRL model predictions showed better agreement with experimental data, in comparison with RANS and DDES model predictions. Both RANS and the new HRL model predictions of the turbulent kinetic energy profiles exhibited qualitatively good agreement with the experimental measurements, while the DDES model results agreed less well. Simulations using the Detached Eddy Simulation (DES) model, DDES model, and the new HRL model were performed for the flow field analysis of the airfoil with ice shape. Computations of DES, DDES, and new HRL model are still not rigorously comparable to the experiments as these computations have not yet attained statistically stationary flow fields. However, the qualitative assessment of the computations shows that the new HRL model enhances shear layer breakup and rollup in the separated flow region more so than do either DES or DDES.