The Influence of Leading Edge Separation on the Unsteady Response of a Thin Airfoil

Abstract

Abstract An experimental investigation of the influence of a leading edge separation region on the unsteady aerodynamic problem for thin, symmetric airfoils exposed to periodic gusting was performed in a subsonic indraft wind tunnel. Two leading edge shapes for the airfoil were used to examine the influence of flow separation both in the unsteady velocity and pressure fields. It is shown that flow separation near the leading edge causes a sharp increase in the unsteady RMS velocity and unsteady surface pressure variation associated with the gust frequency. This also causes a departure from the expectation that the gust information is convected downstream by the freestream in the velocity field. In the absence of such a separation region, velocity and surface pressure results closely resemble inviscid theoretical predictions and expectations. Accurate prediction of unsteady pressure is crucial in estimating the acoustic production of the system.