THE SHOCK-VORTEX INTERACTION - THE ORIGINS OF THE ACOUSTIC-WAVE

In this paper we discuss the mechanisms responsible for the formation of the acoustic wave when a shock interacts with a vortex. Experimenta l measurements have shown that this interaction produces a primarily q uadrupolar acoustic wave with a strong compression attached to the sho ck front. We review earlier work which shows that this strong compress ion is due to the distortion of the shock. The origin of the quadrupol ar component is examined by comparing two-dimensional computations of the shock-vortex interaction to those of an isolated elliptical vortex . The elliptical vortex is similar to the compressed vortex produced w hen a shock interacts with an initially circular vortex. We concentrat e on interactions in which the shock transit time is short. The pressu re field of the shock-vortex interaction is compared to that of an ana logous isolated elliptical vortex for three cases: a weak shock intera cting with a weak vortex, a strong shock interacting with a weak vorte x, and a strong shock interacting with a strong vortex. Our results in dicate that both shock distortion and vortex compression are important to the formation of the acoustic wave.