Dynamic stall analysis using harmonic balance and correlation-based γ-(Reθt)over-bar models for wind turbine applications

In this paper, we use the harmonic balance method to study an oscillating S809 airfoil in dynamic stall. The periodic behavior of this problem makes it well suited for the harmonic balance method, which is able to model unsteady aerodynamics at greatly reduced computational costs when compared with time-accurate unsteady-flow solvers. A finite-volume technique based on the lower-upper symmetric Gauss-Seidel scheme with Roe fluxes is used to solve the Reynolds-averaged Navier-Stokes equations. The turbulent viscosity is computed with the one-equation Spalart-Allmaras turbulence model. In addition, the laminar-turbulent transition is modeled using a correlation-based approach originally developed by Langtry and Menter. Comparisons with experimental data for steady flows with the S809 airfoil highlight the necessity of the transition model to accurately predict the onset of static stall. For unsteady cases, the transition model provides improved agreement with experimental data, predicting dynamic stall when the fully turbulent model cannot. Copyright (c) 2014 John Wiley & Sons, Ltd.