VORTEX-GENERATED SOUND IN FLOW ABOUT SPINNING CYLINDERS

Abstract

This study provides a computational insight into unsteady far-field and surface pressure developed by vortex interaction with multiple rigid bodies in lift conditions. Flows around a spinning cylinder and two cylinders in tandem were taken as simple but yet representative prototypes of flows around multi-element lifting devices. The unsteady Euler equations are solved in terms of propagating disturbances originating from deforming vortices in the mean flow developed in the neighborhood of cylinders. Numerical errors associated with the discretization and boundary conditions were kept small employing a high-order scheme with accurate nonreflecting boundary conditions. To model the interaction of vortices with rigid bodies using moderate amount of computational resources, we apply a single-grid approach and implement the bipolar coordinate transformation where applicable. We address here the amplification of sound by the mean flow with nonzero circulation, strong influence of vortex profile on the generated sound waves, and different degree of amplification of sound in lifting flows for localized and nonlocal vortices. We find that the flow about a cylinder not only amplifies the sound strength but it also shifts the sound directivity. Vortices deforming within the flow about cylinders placed in tandem and in the traverse layouts were examined.