The effects of hydrostatic pressure on conditions in and near a collapsing cavitation bubble

It has long been understood that the conditions within a collapsing cavitation bubble become more extreme as hydrostatic pressure increases, but quantification of these conditions requires estimating the temperature, pressure, and density of the plasma in the bubble, a difficult task. To provide this information, we conducted numerical simulations using the plasma physics hydrocode HYADES, a 1-D, three-temperature, Lagrangean hydrodynamics, and energy transport code. The contents of a bubble at the center of a sphere of water at 1–3000 bars were specified at time = 0, and the bubble was driven by a spherically converging pressure wave of various frequencies (2.5–26 kHz) and amplitudes (10–3000 bars). Results were obtained for temperature, pressure, and density within and immediately outside the bubble. Calculations for bubble radius and the velocity and amplitude of the radiated shock wave compared well with experimental measurements at modest hydrostatic pressures (1–300 bars). At higher pressures, the maximum temperature within the bubble increases above 100 eV, the shock amplitude becomes greater than 1 Gbar, and its propagation speed is up to Mach 100. Also, the shock front heats the fluid, stimulating photon emissions in the liquid [Impulse ACPT contract No. W9113M-07-C-0178.]