An example for the sound production of the vortex surface interaction

The production of sound by the unsteady interaction of two rectilinear vortices in the proximity of a circular cylinder without mean flow is investigated by the potential theory. The paths of the vortices are calculated by the Runge Kutta method. The calculated vortex paths can be approximated to circular motion relative to the centroid of the vortices, and so the centroid of the vortices relative to the centre of the circular cylinder when the vortices are close to each other. The force per unit length acting on the circular cylinder is calculated by the force that is needed to keep the image vortices moving in the assumed paths, and the far field sound produced by the vortex surface interaction is cabulated numerically. The vortex circulations, initial position and separation distances are shown to be the primarily factors which affects the production of sound.