Pitching airfoil subjected to high amplitude free stream oscillations

Abstract

An experimental investigation was carried out to quantify the aerodynamic lift acting on a NACA 0018 airfoil subjected to combined pitching and surging and to compare the results to established theories. A dedicated unsteady wind tunnel was employed that produces large surge amplitudes, and airfoil loads were estimated by means of unsteady surface mounted pressure measurements. In-phase and out-of-phase pre-stall pitching and surging cases were considered for different velocity amplitudes. When the flow was fully attached, satisfactory correspondence was observed between experiments and theory. However, differences were observed when trailing-edge separation was present; in particular the shedding of a trailing-edge vortex corresponded with discrepancies between the experiments and theory.