Numerical Investigation of Airfoil Dynamic Stall in Simultaneous Harmonic Oscillatory and Translatory Motion

Abstract

Wind turbine blades are subject to complex flow conditions. For operation in yaw and turbulent inflow, the blade sections appear to execute a motion more complex than a harmonic blade oscillation, which causes dynamic stall. Predictions of dynamic stall caused by simple harmonic oscillation are crucial to efforts in understanding and improving wind turbine performance. Investigation of dynamic stall development caused by a combined oscillatory and translatory motion contributes to better understand blade loading under complex flow conditions. In this paper, numerical predictions of light and deep stall caused by simple oscillatory motion are obtained first. The ability of the numerical solution to predict dynamic stall loads caused by a combined motion is further investigated. The numerical solution is obtained with a factorized, upwind-biased numerical scheme. The turbulent flow region is computed with a one-equation turbulence model. A transition model is used to simulate the transitional flow effects, which play an important role to the overall unsteady flowfield development. The computed results are compared with available experimental data.