Gurney Flap Control Authority on a Pitching Wind Turbine Airfoil

Rotation of the wind turbine blade through the atmospheric shear layer imposes highly unsteady aerodynamic conditions over the blade resulting in stall, unwanted oscillatory loads, and accompanying deflections. In this study, the effectiveness of the Gurney flap in static and dynamic stall regimes has been evaluated for possible flow control applications. The effect of flap height on the lift and moment coefficients has been investigated using time-resolved pressure measurements at a Reynolds number (Re) of 430,000. In addition, velocity field measurements were made using Particle Image Velocimetry (PIV) to further investigate the changes in the physical mechanisms that occur when the flap is deployed. Static results show a significant change in section lift and moment coefficients comparable with conventional flaps. The behavior of the blade in the dynamic stall regime is also highly affected by the presence of the Gurney flap. When the Gurney flap is on the pressure side of the airfoil, lift coefficients increase in all flow regimes. Deployment of the flap on the suction side can still affect the flow in moderate stall conditions even under post stall conditions, although in the deep stall regime the effects are limited.