Dynamics of thin-film breakup in a constricted pore

To understand foam formation in porous media, the dynamics of a wetting liquid film forming an unstable collar (or collars) in a constricted cylindrical tube are considered. A hydrodynamic lubrication analysis is presented to describe the time evolution of a thin viscous film under the influence of surface tension and conjoining or disjoining forces. Time to breakup depends on the pore shape, the strength of the conjoining or disjoining force, the initial film profile, and also, the fluid viscoisty, interfacial tension, and unconstricted pore radius which combine to form a characteristic scaling time. Agreement is found between breakup times predicted from the hydrodynamic analysis, and from 16 mm movies taken of the breakup phenomena over a wide range of initial film thicknesses.