Suppression of Aero-Acoustic Noise Over a Cavity

The aim of this research is to develop a method to suppress the aerodynamic noise generated by a turbulent flow over a cavity. The results of an active control experiment and a passive control experiment are reported. In the active control experiment, the phases of velocity fluctuations along the spanwise direction are changed using piezo-electric actuators, so that the sound waves generated by these velocity fluctuations will eventually cancel each other in the far field. As a result of the active control, an aerodynamic noise suppression of 30 dB is achieved. In the passive control experiment, even a greater noise suppression effect, up to 65 dB is achieved. It is shown that the location and the size of the plate have a strong influence on the noise suppression for passive control.