Controlled leading-edge suction for management of unsteady separation over pitching airfoils

Abstract

The effect on the unsteady surface pressures of controlled suction from a spanwise slot, located at 2% chord in the suction surface of a two-dimensional NACA 0012 airfoil model, was examined in detail for a wide range of pitch rates with a constant velocity ramp motion. The experiments were conducted in the Andrew Fejer Wind Tunnel at the Illinois Institute of Technology's Fluid Dynamics Research Center. The optimum suction required to meet three different control objectives, suppression of the dynamic-stall vortex, delaying detachment of the vortex from the airfoil surface, and maximizing the unsteady lift, was determined for different pitch rates and angles of attack. The pressure data were used to develop specifications for the flow state over the airfoil surface that would meet these objectives. Such specifications are necessary for the development of on-line flow management systems. A procedure was also developed to account for variations in suction and motion history.