Phenomena of a Miscible Drop Through a Stratified Fluid

Abstract

This work describes the dynamics of a drop of benzyl alcohol, (partially miscible in water), as it traverses a stratified fluid formed by two layers, water on the top and salted water with a 1.68 molar concentration on the bottom. The width and stability of the interface depends on the temperature and on the way the upper layer mixes as it is introduced into the container. In this case, the procedure was controlled to produce a stable interface for several minutes, and to have a repeatable experiment. The width and position of the interface was measured each time through shadowgraphs. The processes that occur during the fall of the drop depend on various parameters like its geometry, the width of the upper layer and the density of the lower layer. First the drop seems to have a free fall. After it enters in contact with the interface, the behavior is similar to a damped harmonic oscillator. The drag force was calculated using models for a rigid sphere and for an ellipsoid with varying dimensions. A comparison between the measured and the calculated values is presented in a graph.