Bubble statistics and coarsening dynamics for quasi-two dimensional foams with increasing liquid content

TL;DR

This study investigates bubble size, shape, and coarsening in quasi-two-dimensional foams with variable liquid content, revealing how increased wetness affects coarsening dynamics and the applicability of von Neumann's law.

Contribution

It introduces a model incorporating border blocking effects to explain deviations from von Neumann's law in wetter foams, supported by experimental data.

Findings

Bubble distributions are independent of time and liquid content in the scaling state.

Average coarsening rate decreases with increasing liquid content.

Von Neumann's law is progressively violated as foam becomes wetter.

Abstract

We report on the statistics of bubble size, topology, and shape and on their role in the coarsening dynamics for foams consisting of bubbles compressed between two parallel plates. The design of the sample cell permits control of the liquid content, through a constant pressure condition set by the height of the foam above a liquid reservoir. We find that in the scaling state, all bubble distributions are independent not only of time but also of liquid content. For coarsening, the average rate decreases with liquid content due to the blocking of gas diffusion by Plateau borders inflated with liquid. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and with decreasing bubble size. We successfully model this behavior by explicitly incorporating the border blocking effect into the von Neumann argument. Two dimensionless bubble shape parameters naturally arise, one of which is primarily responsible for the violation of von Neumann's law for foams that are not perfectly dry.