Modeling of the Generation and Collapse of Aqueous Foams

Abstract

Drainage of the continuous phase liquid from a foam plays a pivotal role in determining its stability to collapse. A theoretical model for the drainage of the liquid during generation of a foam by bubbling and its subsequent collapse is presented. The model accounts for drainage in the films as well as in the plateau border channels. Drainage of the films is modeled using Reynold's equation for the flow between parallel flat circular disks under the influence of van der Waals, electrical double-layer, and plateau border suction forces with film rupture occurring when the film thickness attains a certain critical value. Since this model accounts for collapse at the foam/gas interface during generation, it is able to predict the steady state height attained by pneumatic foams. The model is also able to predict the establishment of a drainage equilibrium when the opposing forces of gravity and plateau border suction gradient balance each other. The effect of various parameters such as superficial gas velocit...