CONTROL OF WALL-SEPARATED FLOW BY INTERNAL ACOUSTIC EXCITATION

This paper explores the control of wall-separated flow on a NACA 633-018 airfoil and a circular cylinder by using the internal acoustic excitation technique. Experimental study of the characteristics of the flow under internally emanating acoustic waves is performed in an open-type, suction wind tunnel. Tests are carried out at the Reynolds number ranging from 6.3 × 103 to 5.0 × 105 based on the relevant characteristic lengths, the airfoil chord, and the cylinder diameter. The control effectiveness is verified by the measurements of parameters such as the excitation frequency, the excitation level, and the forcing location. Data indicate that the excitation frequency and the forcing location are the key parameters for controlling the separated flow, and the forcing level is the least-effective parameter for the study. As long as the emanating acoustics is “locked in” to the separated shear-layer instability frequency and forcing is applied at the separation point, the separated flow is controlled most effectively. Moreover, the lift is increased and the drag reduced dramatically. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.