Title: Bubble kinetics in a steady-state column of aqueous foams

Author (Talk): Klebert Feitosa, University of Pennsylvania

Abstract:

We measure the liquid content, the bubble speeds, and the distribution of bubble sizes, in a vertical column of aqueous foam generated and maintained in steady-state by continuous bubbling of gas into a surfactant solution. Nearly round identical bubbles accumulate at the solution/foam interface and subsequently rise with constant speed. Upon moving up the column, they become larger due to gas diffusion and more polyhedral due to drainage. While the size distribution is monodisperse near the bottom and is polydisperse near the top, there is an unexpected range of intermediate heights where it is bidisperse with small bubbles decorating the junctions between larger bubbles. We explain the evolution in both bidisperse and polydisperse regimes, using Laplace pressure differences and taking the liquid fraction profile as a given.