The effect of static pressure on the inertial cavitation threshold and collapse strength.

Abstract

The conditions within an inertially collapsing bubble are known to produce high temperatures and pressures. Previous investigators have proposed various mechanisms for driving the collapse in order to maximize the energy density of the bubble’s contents. Working in fluids at high static pressures (up to 30 MPa) has shown some promising results. Preliminary data indicate that the strength of the collapse scales with the static pressure in the fluid. We report here the results of a series of rigorous experiments designed to better define this relation at the threshold of inertial cavitation. The hydrostatic pressure dependence of the inertial cavitation threshold in ultrapure water was measured in a radially symmetric standing wave field in a spherical resonator driven at 26 kHz. At this threshold, the collapse strength will be reported in terms of the resulting photon radiance below 400 nm and the relative shock wave amplitude. These experimental results will be compared to predictions of collapse strength. [Work supported by Impulse Devices, Inc.]