Optical-velocimetry, wake measurements of lift and induced drag on a wing

Particle Tracking Velocimetry was used, in a low-speed wind-tunnel study, to obtain simultaneous cross-flow velocity measurements in three planar regions downstream of an airfoil having a NACA 0015 profile. In order to measure both the total lift and induced drag, and their distributions on the airfoil, a wake integration technique based on the control volume approach was used. The airfoil model was tested in clean wing configuration and with a 3.33% Gurney flap attached to the trailing edge. The Gurney flap was found to increase the complexity of the wake and cause a systematic increase in lift and induced drag values. The changes in total lift and induced drag resulting from the fitting of a Gurney flap compared very favourably to investigations using traditional aerodynamic techniques demonstrating the validity of the method.