Particle drift near an oscillating bubble

The drift of fluid particles induced by a bubble oscillating with motions typical of a single sonoluminescent bubble is considered. In the first calculation the bubble is assumed to remain spherical and to oscillate both radially, with large amplitude motion, and laterally, with a smaller amplitude. The paths of marked particles are traced by numerical integration of the velocity field. It is found that the resulting drift motion at large distances from the oscillating sphere is similar to a steady dipole flow. The strength of the dipole, however, is typically seven orders of magnitude less than the streaming motion observed in the laboratory by Lepoint-Mullie et al. A second calculation supposes that the bubble does not remain spherical but collapses asymmetrically, with one side falling inwards towards the other at a greater speed. The resulting impulse again induces a dipole motion in the far field, whose strength may be estimated on certain assumptions. It is found to be quite comparable to that observed.