Flow along two dimensions of liquid pulses foams: experiments and theory

Experiments on foam drainage have so far only been performed in essentially one-dimensional flow geometries aligned with the direction of gravity. Here a foam-filled Hele-Shaw cell is used to examine pulsed drainage, which is the flow of a finite liquid volume, both along and perpendicular to the direction of gravity. An exact similarity solution to the generalized foam drainage equation exists, and an asymptotic analysis is presented to elucidate the nonlinear dynamics of the model. Good qualitative and quantitative agreement between theory and experiments on aqueous foams made with SDS surfactant is found when the node-dominated foam drainage model is applied.