Influence of Enveloping Water Layer on the Rise of Air Bubbles in Newtonian Fluids

Abstract

The rise of air bubbles in five Newtonian fluids is compared for two different cases of bubble formation and release: (a) directly into the five homogeneous fluids and (b) directly into a layer of distilled water underlying each one of the five liquids. It was found in Case (b) that medium-sized bubbles rise steadily through the upper liquid with an enveloping water layer of variable thickness. The influence of this water layer on the trajectory, shape, and terminal velocity of bubbles is particularly significant in low viscosity upper phases. The resulting water mass transfer per bubble through the lower density upper phase depends on viscosity and was markedly greater for the higher viscosity fluids. The behavior and the nature of the detachment of the water layers from the larger size bubbles are also presented and discussed.