The experimental results of the wake measurements downstream of a sinusoidally pitching NACA 0012 Airfoil about the quarter chord axis using hot wire anemometry are presented.
Mean velocity and turbulence intensity profiles were measured at various downstream locations for the cases of three mean incidence angles, $\alpha_0$ =0˚, 2˚ and 4˚ and for two different reduced frequencies K=0.1 and 0.2. Reynolds number based on chord length was 47000 for K=0.1 and 27000 for K=0.2.
It was observed that the instantaneous angle of attack at which the wake thickness suddenly increases was increased. This suggested that the unsteady separation over the oscillating airfoil surface was not governed by the instantaneous angle of attack. Rather, it seemed to be governed by the time history of the airfoil motion.