### 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.]