Preliminary experimental observations of the effects of buoyancy on single-bubble sonoluminescence in microgravity and hypergravity

Abstract

The buoyancy force [given by the product of the density of the liquid, the gravitational constant, and the volume, ρgV(t)] may play an important role in the stability of small bubbles undergoing highly nonlinear radial pulsations. In particular, during a single acoustic cycle, a sonoluminescence bubble undergoes volume changes on the order of 1000, and thus the buoyancy force changes by this same factor. Since the equilibrium position of such a bubble in a standing wave is balanced by the Bjerknes and buoyancy forces, the bubble may be subjected to large translational velocities and accelerations during each acoustic cycle [S. M. Cordry, Ph.D. thesis, U. M. (1995) and J. Acoust. Soc. Am. 97, 3375 (1995)]. The buoyancy-force stability issue was examined in a series of experiments aboard a NASA KC-135A, which performs parabolic maneuvers to generate limited periods of microgravity. Effects were examined in both microgravity and hypergravity (≊ 0 and 2 g, respectively). Results of this study, performed in November 1995 in the Netherlands, under the auspices of the European Space Agency, will be presented. [Work supported by NSF, CPAC, NASA, and ESA.]