Using an Active Gurney Flap to Improve the Aerodynamic Performance of a Wind Turbine Blade*

A Gurney flap - a small vertical tab installed near the trailing edge of the pressure surface of a wing - is often used to modify aerodynamic performance and increase the down force in race cars. Here we report the design, fabrication and testing of an ``Active Gurney Flap'' (AGF) which can be raised and lowered on demand, and is proposed for use on wind turbines to provide real-time control of the aerodynamic and structural loads experienced by the turbine blade. The torque required to raise and lower the flap was measured on a flat plate wind tunnel model, and a turbine blade wing section (chord = 0.25m, span = 1m) was fabricated and tested over a range of angles of attack at Reynolds numbers between 160,000 and 414,000. Lift and Pitching moments were measured using an aerodynamic sting. We find that the deployment torque is largely independent of Reynolds number and deployment speed. The AGF increases the lift and pitching moment of the wing over a wide range of angles of attack, with some dependence on Re, which affects the boundary layer transition and separation.