Coalescence in a steady-state rising foam

Steady-state rising foam is an ideal medium for studying foam coalescence phenomena. The coalescence process in this type of foam is characterized analytically. The spatial distribution of bubble size depends on the effect of individual coalescence events on the bubble size distribution, the rate at which they occur, and the rise rate of the bubbles. The film rupture rate is assumed to depend on the film area and the film drainage time, and is calculated using several simple models. This analysis agrees well with measurements conducted in a laboratory foam cell. However, the time-scale of the experiments indicated that film drainage was occurring predominantly in the hydrodynamic regime, and that non-equilibrium rupture mechanisms were primarily responsible for the observed coalescence.