Steady-state drainage of an aqueous foam

Abstract

The process of wetting of a monodisperse foam by the continuous addition of liquid from the top has been investigated for a cylindrical column. The velocity of the interface between dry and wet foam was found to vary as the square root of the rate of addition of liquid. Evidence of a structural transformation was found around gas fraction \ensuremath{\Phi}=0.87. It was interpreted as arising from the collapse of the four-sided faces of the (Kelvin) polyhedra which constitute the foam cells, and this was directly observed when large bubbles were used. There is a second transition at around \ensuremath{\Phi}=0.6, with the onset of bubble motion.