Experimental Evaluation of an L-Shaped Tab to be Used as an Active Gurney Flap for Dynamic Stall Control

The present paper describes an experimental activity carried out in the frame of research about dynamic stall control. In particular, an L-shaped tab was tested on the trailing edge of a pitching airfoil in deep dynamic stall condition. The L-shaped tab was tested on a NACA 23012 pitching blade section model in two different fixed positions: deployed and retracted. When deployed the tab is flush to the airfoil upper surface and its end prong behaves as a Gurney flap at the airfoil trailing edge. When retracted the tab features an angle of 9.1 deg. with the airfoil upper surface since its prong tip touches the airfoil trailing edge. The experimental activity includes both unsteady pressure measurements on the airfoil midspan contour to evaluate the airloads time histories and Particle Image Velocimetry (PIV) carried out at the trailing edge region. The experimental results shows that the use of such a pivoting L-shaped tab can introduce similar advantages for dynamic stall alleviation to the ones that can be obtained by the use of an active Gurney flap. Therefore, due to an easier integration on helicopter blades, the tested L-shaped tab can be considered an attractive device to be used on helicopter blades for dynamic stall control.