Reflectometry study of interbubble gas transfer in liquid foams

Abstract

We study interbubble gas transfer in liquid foams by measuring the relative decrease of the bubble area from reflectometry. Foams are obtained by independently fixing foaming solution and gas flows through a coarse porous structure. Precise measurements of these flows instantaneously give the gas volume fractions of the foams; real time diffractometry gives their initial bubble size distributions, which we found to be lognormal. — We calculate interbubble gas transfer within such foams on the basis of a theory developed by Lemlich for other bubble size distributions. For a given bubble mean size, we find that the experimentally measured width of the bubble size distribution provides the fastest transfer; then the calculated transfer is close to the one which corresponds to the Lemlich distribution. — Comparison between theoretical and experimental relative decreases of the bubble total area allows to obtain the initial effective permeability of the interbubble medium to gas transfer. We show that this permeability can be drastically lowered by associating an anionic surfactant with an amphoteric one in the foaming solution .