Unsteady Flow Separation at the Leading Edge of a Flat-Plate Airfoil Caused by External Disturbances

Abstract

Under high freestream turbulence, unsteady flow separation can occur at the leading edge of a thin airfoil to lead to the generation of discrete vortices, even at zero incident angle. In the present study, the critical amplitude of external disturbances for its occurrence is investigated by applying acoustic forcing for a flat-plate airfoil. The results show that even at the literally sharp leading-edge, the intensity of external disturbance for the excitation of vortices is as high as 5% of U_∞ in terms of v (normal-to-plate) fluctuation.