Experimental Investigation of Aerodynamic Phenomena in the Wake of a Rapidly Stalled Wing.

Abstract : By means of wind-tunnel experiments, aerodynamic phenomena were investigated in the wake of a rapidly stalled two-dimensional wing. Experiments were performed to study the effect of wing pitch rate, model size, and leading edge details on vertical and horizontal perturbation velocities downstream of the wing. Large vertical wake velocities (peak-to-peak values up to 160 fps), transient in nature, were measured during early times following a pitchup maneuver. The magnitude of this velocity was a function of the pitch rate parameter. Large steady-state buffeting velocities (peak-to-peak values up to 160 fps) were also measured in the wing wake. A result of particular significance to aircraft tail surface design was that the steady-state buffeting was strongly periodic throughout the tested Reynold's number range (680,000 to 1,360,000). A simplified dynamic analysis of the C-2A horizontal tail for a velocity input representative of the steady-state buffeting experimental results indicated that this condition could produce the large loads measured during flight test maneuvers. (Author)