Manipulation of the Flow Around a Circular Cylinder by Utilizing the Flow Receptivity

An attempt to control the flow around a circular cylinder by utilizing the receptivity to the external acoustic disturbance was carried out and its mechanism was also studied. The velocity fields around the cylinder vicinity are carefully investigated with an X-type hot-wire probe. When the disturbance of a higher frequency related to the separated shear layer instability is added, the development of turbulence and the spreading of the shear layer are restrained. And, the amplification of the fluctuating velocity component of the Karman vortex shedding is delayed and its degree is reduced. Furthermore, the process of the gradual scale modification of the shear layer instability that appears prior to the transition of the flow is suppressed.