Effects of a background axisymmetric potential flow on vortex ring pairing sound

Abstract

Sound generated by the pairing of two coaxial vortex rings in the presence of a background axisymmetric potential flow was studied numerically. Results show that the background flow substantially affects the sound generation process in the beginning of the vortex ring interaction. They also suggest that the axial jerk and radial acceleration/deceleration of vortex rings are the major mechanisms through which pairing sound is produced. The effect of background flow mean shear rate on sound generation is also discussed and the results suggest that higher sound levels will be generated when the vortex rings are interacting within the region of high mean shear in a low speed laminar jet.