Method for reducing the periodical pressure variations of an external stream flowing around the opening of a cavity

摘要

The method involves periodically changing the direction of a flow passing over a cavity to counter the actual pressure changes in a cavity. The change of flow direction is made with the appropriate phase using a deflector in the region of the front edge of the opening to the cavity. The curvature of the deflector may be altered using an electric motor, a piezo actuator, pneumatic or hydraulic piston or an electro-dynamic actuator such as a loudspeaker coil.