Particle Drift Near an Oscillating Cavity

Abstract

Different mechanisms for the generation of light by a sonoluminescent bubble have been proposed, which involve the shape of the bubble near the time of its minimum radius. Since the shape is difficult to observe directly, the author has suggested obtaining further information by studying the drift motions in the fluid surrounding the bubble, which should be observable out to distances of many times the bubble radius. In this paper two theoretical models are considered. In one, a spherical cavity oscillates both radially and laterally, with amplitude comparable to the mean radius of the bubble. This is shown to produce steady drift motions having the form of an axial dipole flow. The strength of the dipole, however, is many times smaller than that seen in recent observations. In the second model the bubble is assumed to collapse asymmetrically, with one wall hitting the opposite wall at high velocity. This again produces a dipole flow in the far field, and the strength of the flow is compatible with that observed.