Viscous streaming from an oscillating spherical bubble

Asymmetric patterns of streaming around a single sonoluminescent bubble have been observed by Lepoint-Mullie and co-workers. The present paper considers theoretically the viscous streaming from a spherical bubble undergoing small radial and lateral oscillations simultaneously, using an extension of the method of Davidson & Riley so as to include radial oscillations. On the assumption that the radial and lateral oscillations are of comparable magnitude, it is shown that the presence of the radial oscillations greatly enhances the streaming. The streaming is greatest when the phase difference between the oscillations is +/-90 degrees, and reverses in direction when the phase difference passes through zero or 180 degrees.