Numerical studies on dynamic stall characteristics of a wind turbine airfoil

Abstract

The present work delivers an evaluation of the S809 airfoil under static and dynamic conditions employing a computational fluid dynamics (CFD) approach. Pitching motions with three different mean angles of attack, 8°, 14° and 20°, with a reduced frequency of 0.079 and amplitude of 10° were imposed at a quarter chord position. Two widely used eddy-viscosity turbulence models, Spalart-Allmaras (SA) and Menter shear-stress-transport (SST), were tested to capture the static and dynamic behavior of the flow. A high order flux discretization, weighted essentially non-oscillatory (WENO) scheme was used in these computations to better resolve the detaching vortices. The results were validated against experimental data and an empirical correlation according to the Leishman-Beddoes model with reasonable agreement. The SA model gave the best prediction in the post-stall regime at high angles of attack. The pressure evolution and the flow field surrounding the airfoil in the onset of dynamic stall were presented and evaluated.