Active Control of Cascade Flutter by Means of Sound Waves from Duct Wall Sources.

Abstract

The purpose of this paper is to investigate how one can control and suppress cascade flutter by means of sound waves. The model considered herein is a three-dimensional linear cascade of flat plates oscillating in a subsonic uniform flow between parallel walls. A sidewall of the model is partially made of actuator surface like a loudspeaker which generates sound waves with the same frequency as that of the blade vibration. The aerodynamic work exerted on a blade due to oscillating motion of the cascade itself and due to the motion of the actuator wall surface are calculated. The required amplitude of the actuator wall surface (i.e., the loudspeaker membrane) to suppress the cascade oscillation is also estimated. Numerical results show that the loudspeaker can work most effectively when the center line of the membrane is located just upstream of the leading edge line of the cascade or when the leading edge line of the membrane is located near the trailing edge line of the cascade. The phase difference between vibrations of the cascade and the actuator surface is also an important parameter.