Dynamics of Stable Cavities during Acoustic Cavitation

Abstract

Stable cavities in a field of acoustic cavitation are small gas-filled cavities that have a lifetime which is long compared with the period of the sound field. The oscillations of such cavities in liquids under the influence of a sinusoidal pressure field have been studied to gain insight into mechanisms important in phenomena associated with acoustic cavitation, such as erosion and chemical reactions. A nonlinear differential equation for the motion of the interface of a stable cavity has been solved numerically on a digital computer and analytically by an iterative method. Stable cavities, which may pulsate through many periods of the sound field, may be contrasted with transient cavities whose lifetimes are short compared with the period of the sound field. A transient cavity is a small gas-filled bubble that on expansion to some maximum size contracts violently; during most of the collapse phase a transient cavity acts as though it contained only vapor. The transformation of stable cavities into transient cavities as a function of frequency and pressure will be discussed. (This research is supported by the Office of Naval Research.)