SEARCH

SEARCH BY CITATION

Abstract

When a small drop or bubble approaches a fluid-fluid interface, a thin liquid film forms between them and begins to drain. As the thickness of the draining film become sufficiently small [about 1,000 Å (100 nm)], the effects of the London-van der Waals forces and of the repulsive force of any electrostatic double layer become important. Lin and Slattery (1982b) developed a hydrodynamic theory for the first portion of the coalescence process: the drainage of the thin liquid film while it is sufficiently thick that the effects of London-van der Waals forces and of electrostatic forces can be ignored. Here the effect of the London-van der Waals forces are included. Given only the drop radius and the required physical properties, the configuration of the film as a function of time is predicted. For the case of a negative disjoining pressure, it is possible to estimate an upper bound for the coalescence time or the time during which a small drop or bubble appears to rest at a phase interface before it coalesces under the influence of London-van der Waals forces.