Passage of a liquid drop through a liquid-liquid interface

Abstract

A liquid drop passing through a liquid-liquid interface (three phase system) is studied in the present work. Behavior of the drops at a pure interface is compared with that an impure interface and also with that of a rigid sphere at a pure liquid-liquid interface. Numeical solutions of the coupled momentum and energy equations are obtained by employing a geometrical model for a spherical drop passing through a pure liquid-liquid interface. Interfacial oscillations, film rupture and circulation inside the drop are considered in the present work. Expressions are developed for the instantaneous drop velocity, the velocity of approach and the film thickness. Velocity profiles in the draining film are also calculated. At very short times the velocity profile is not parabolic and there is a reversal in flow as we approach the interface. At larger times, the velocity profile approaches a parabolic distribution. The present results clearly show that as the drop approaches the interface for drops below the critical size, the interface deforms, becomes unstable and the drop oscillates. Photographic observations of the passage of water drops and rigid spheres through liquid-liquid interfaces reveal that there was no film rupture in the case of a rigid sphere at a pure interface while in the case of a liquid drop at a pure liquid-liquid interface, the film ruptured near its edge, but in the case of liquid drops at an impure interface, the rupture was on the rear hemisphere of the drop. © 1972.