The instability of liquid surfaces when accelerated in a direction perpendicular to their planes. II

Abstract

An apparatus for accelerating small quantities of various liquids vertically downwards at accelerations of the order of 50g ( g being 32.2 ft./sec. 2 ) is described, and the behaviour of small wave-like corrugations initially imposed on the upper liquid surface has been observed by means of high-speed shadow photography. The instability observed under a wide variety of experimental conditions has been analyzed, and the initial phases have been found to agree well with the first-order theory given in part I. When the disturbance has attained a considerable amplitude the first-order equations cease to apply and it changes from a wave into a form which has the appearance of large round-ended columns of air extending into the liquid and separated by narrow sheets of liquid. The air columns attain a steady velocity relative to the accelerating liquid and continue to penetrate into the liquid until the lower surface of the liquid is reached. In spite of these very large surface disturbances, the main body of liquid below them is accelerated as though they did not exist.