Sound sources in the interactions of two inviscid two-dimensional vortex pairs

The sources of sound during the interactions of two identical two-dimension al inviscid vortex pairs are investigated numerically by using the vortex s ound theory and the method of contour dynamics. The sound sources are ident ified and then separated into two independent components, which represent t he contributions from the vortex centroid dynamics and the microscopic vort ex core dynamics. Results show that the sound generation mechanism of the l atter is independent of the type of vortex pair interaction, while that of the former depends on the jerks, accelerations and vortex forces on the vor tex pairs. The power developed by the vortex forces is found to be importan t in the generation of sound when the vortex cores are severely deformed an d their centroids are close to each other. The isolated source terms also e xplain the appearance of wavy oscillations on the time variations of the so und source strengths in the vortex ring and the two-dimensional vortex inte raction systems.