Measurement of cavitation acoustic pressure and bubble dynamics in liquid helium II

Abstract

Acoustic cavitation nucleated in bulk He II at a temperature of 2.10°K was photographed at 6000 frames‐per‐second. The vapor bubbles were formed at pressure antinodes near the axis of a PZT4 cylindrical transducer operating at 52 KHz with a wavelength of 4.4 mm. The diffraction pattern of light traveling along the cylinder axis was used to adjust the frequency for maximum acoustic intensity and to measure the acoustic pressure. For a pressure of 280:± 70 mbar rms, spherical bubbles originating in the liquid grew to 1 mm diameter in less than 0.3 msec. They fragmented during the next 0.6 msec to form smaller nonspherical cavities which persisted for tens of milliseconds. The smaller nonspherical cavities could also be observed at lower acoustic pressures where they originated on the surface of a probe and not in the bulk fluid. Previous photographs of He II cavitation [A. Mosse, M.L. Chu, and R.D. Finch, J. Acoust. Soc. Am. 47, 1258 (1970)] showed similar nonspherical cavities without revealing their origin.