Experimental Detection and Pulsed Jets Control of Turbulent Boundary Layer Separation

Abstract

Wind tunnel experiments are conducted to investigate the effect of constant and periodic blowing on flow separation from a non-slotted NACA-type flap which is equipped with seven pulsed jets actuators and tested at Re 10 6 through different deflection angles from 2 to 35 • . Laser beam tomoscopy is first used to visualize flow structures with and without flow control. The recirculation zone length is mainly estimated by means of wall shear stress measurements provided by hot-film gauges which are chordwise distributed on the flap. Two separation criteria based on higher-order statistical moments are proposed to detect the flow separation location. They are practised in the uncontrolled, constant blowing and periodic blowing cases. The two criteria are finally applied to follow the open-loop response of the system and determine the system static map local gradient in an attempt to evaluate the feasibility of extremum-seeking approach of closed-loop control.