Gas Diffusion by Pulsating Bubbles in Sonic Fields

Abstract

A pulsating gas bubble is suspended by an acoustic radiation pressure force in a liquid. The bubble is far from all boundaries and virtually stationary. When the sound field is relatively weak and the liquid is undersaturated with the gas in question, the bubble shrinks under the influence of normal diffusion of gas into the liquid. When the liquid is saturated and the sound field relatively strong, the bubble may grow or shrink under the opposing influences of surface tension pressure and sonic pressure (rectified diffusion). Measurement of the diameter of the bubble as a function of time permits, in the first case, determination of the diffusion constant for the gas-liquid system, and, in the second case, experimental evaluation of current theories of sonically induced rectified diffusion. It is found that when a bubble breaks into surface oscillations, whichever process it is undergonig at the time, either growth or decay, is enhanced. [This work was supported in part by NIH grant while the author was on sabbatical leave during the academic year 1966–67 at the University of Vermont, Burlington, Vermont.]