THE DYNAMICS OF LIQUID-FILM BREAKUP IN CONSTRICTED CYLINDRICAL CAPILLARIES

To understand foam generation in porous media, this work considers the dynamics of a wetting viscous film forming an unstable collar (or collars) in a constricted cylindrical capillary. A nonlinear evolution equation is derived and solved numerically to determine the evolution in time of a liquid film deposited by a bubble after it has moved through a constricted capillary. Results show that time to break up depends on the initial film profile, the film thickness, the pore geometry, and also on the fluid viscosity, interfacial tension, and unconstricted capillary radius which combine to form a characteristic scaling time. Excellent agreement is found between breakup times predicted from the hydrodynamic analysis and experimental breakup time data over a wide range of initial film thicknesses and fluid properties. New data for the dynamic collar shape also agree well with the theoretical results. © 1990.