Rectified Diffusion during Nonlinear Pulsations of Cavitation Bubbles

Abstract

A gas-filled bubble in a liquid will generally dissolve because of diffusion of gas out of the bubble into the surrounding liquid. However, when set into motion by an acoustic field, a bubble may grow by a process called rectified diffusion. This process can counteract the effect of diffusion for values of the acoustic-pressure amplitude greater than some threshold value. This threshold has been determined by a theory that uses computed radius-time curves for bubbles pulsating nonlinearly rather than assumed infinitesimal, sinusoidal motions. For radius-time curves calculated by a digital computer, this threshold has been computed for a sequence of values of gas concentration, bubble radius, and acoustic frequency. [This work was supported by the U. S. Office of Naval Research (Code 468).]