On the Wall Interaction of Compressible Vortex Rings and Associated Noise

Abstract

Sound generated during the interaction of a compressible vortex ring with wall has been studied experimentally. Compressible vortex rings are generated from the open end of a short driver section shock tube for shock Mach numbers 1.31 and 1.55. The intensity of sound produced during the wall interaction of vortex ring is measured and compared with the sound generated from other phenomena such as the formation and evolution of vortex ring and shock-vortex interaction. Noise associated with the distinct phenomena during wall interaction such as vortex stretching, secondary-wall-vortex formation and its interaction with primary ring is identified using Discrete Wavelet Transform of measured acoustic pressure signal. The related flow field is verified with high speed flow visualization pictures. It has been observed that the noise generated during the interaction of vortex with wall is more than the noises generated during the evolution of vortex ring and shock-vortex interaction for higher shock Mach numbers. As the shock Mach number increases wall interaction noise becomes dominant and the acoustic pressure signatures become very sharp like shock signatures.