Analysis of Turbulent Separated Flows for the NREL Airfoil Using Anisotropic Two-Equation Models at Higher Angles of Attack

Abstract

Numerical simulations of the turbulent flow fields at stall conditions are presented for the NREL (National Renewable Energy Laboratory) S809 airfoil. The flow is modeled as compressible, viscous, steady/unsteady and turbulent. Four two-equation turbulence models (isotropic k–ε and q–ω models, anisotropic k–ε and q–ω models), are applied to close the Reynolds-averaged Navier-Stokes equations, respectively. The governing equations are integrated in time by a new LU-type implicit scheme. To accurately model the convection terms in the mean-flow and turbulence model equations, a modified fourth-order high resolution MUSCL TVD scheme is incorporated. The large-scale separated flow fields and their losses at the stall and post-stall conditions are analyzed for the NREL S809 airfoil at various angles of attack (α) from 0 to 70 degrees. The numerical results show excellent to fairly good agreement with the experimental data. The feasibility of the present numerical method and the influence of the four turbulence models are also investigated.