Control of aeolian tones radiated from a circular cylinder in a uniform flow

Effects of artificial forcing on the generation and propagation mechanisms of the sound generated by a circular cylinder in a uniform flow are investigated by direct solution of the two- dimensional, unsteady, compressible Navier - Stokes equations. Two types of forcing are considered: rotation of the cylinder at a constant angular velocity and periodic blowing/ suction from the (nonrotating) cylinder surface. For the case of a rotating cylinder, results show that the sound generation can be controlled by controlling the periodic shedding of (Karma) vortices from the cylinder surface into its wake. On the other hand, results for the case of periodic blowing/ suction show that the generation and propagation of the sound can be effectively controlled without drastic changes of the vortex shedding. It is found in this case that the interactions among the lift dipole ( which is generated by the vortex shedding), the drag dipole and the monopole (both of which are generated by the periodic blowing/ suction) play a principal role in the control process of the generation and propagation of the sound. (C) 2003 American Institute of Physics.