ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aPAb7. Mass diffusion in spark-induced vapor bubbles.

J. S. Allen

M. A. Averkiou

L. A. Crum

Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105

C. M. Young

G. R. Hess

Tetra Corp., Albuquerque, NM 87109-4512

The diffusion of gas into a spark-generated vapor bubble is shown to be an important factor when attempting to generate repeated oscillations of the bubble. Predictions for the radius--time curve based on the Trilling equation are matched with experimental measurements and the equilibrium radius is deduced. The effect of the ambient, hydrostatic, and vapor pressures of the liquid on the bubble collapse time is demonstrated. The high-frequency approximation of the first-order solution of the Eller--Flynn formulation for mass diffusion is utilized to estimate the amount of gas diffused into the bubble at the end of a single cycle. An increase in the bubble radius and collapse time is noted and this process is repeated for an extended number of cycles. The frequency signature of the resulting bubble oscillation is analyzed. The increase in the bubble radius and the period of oscillation due to diffusion, and the gas-microbubble residues remaining after collapse, have potentially important effects when generating a repeated sequence of vapor bubbles, as in extracorporeal shock wave lithotripsy. [Work supported in part by the U.S. Navy and the National Institute of Health.]