Dynamics of foam films in constricted pores

Hydrodynamics of foam films in a porous medium depend strongly on the pore geometry, foam quality, foam flow rate, surfactant formulation, rheological properties of the film, and the capillary pressure in the medium. These dynamics were studied numerically by simulating the behavior of a foam film as it traverses a periodically constricted sinusoidal pore. Different regions of film behavior exist depending on ifs rheological properties. For a film with rigid (immobile) surfaces, the entrainment effect leads to a thickening film consistent with related phenomena such as Bretherton's (1961) analysis of a bubble moving in a capillary tube. A film with mobile surfaces, however, stretches and thins while remaining uniform in thickness and may become unstable under certain conditions. The dependence of limiting capillary pressure on the foam flow rate and rheological properties is explained quantitatively.