Numerical Simulation of Surface Roughness Effects on Dynamic Stall of Wind Turbine Blade

Abstract

Horizontal axis wind turbines can experience significant time varying aerodynamic loads, potentially causing adverse effects on structures, mechanical components, and power production. As designers attempt lighter and more flexible wind energy machines, greater accuracy and robustness will become even more critical in future aerodynamics models. Aerodynamics modeling advances, in turn, will rely on more thorough comprehension of the three dimensional, unsteady, vortical flows that dominate wind turbine blade aerodynamics under high load conditions. These variations may express the incidence angle and wind velocity changes over a 2-D S809 airfoil with the surface roughness effect. To numerically characterize these flows, the instantaneous speed and wind direction variations, represented by a peak function were used to characterize dynamic stall vortex kinematics and normal force amplification. For lack of experimental data in the pulsating motion case, the present numerical approach has been validated by comparing our results with an oscillating S809 airfoil experimental data. The results show the importance of taking into account the behaviour of the unsteady flow subject to abrupt variation of wind direction and velocity. As well as the influence of the surface roughness in the modelling of wind turbine flow. These results give an accurate estimation of aerodynamic loads which will subsequently improve the design of wind turbines.