Effects of London‐van der Waals forces on the thinning and rupture of a dimpled liquid film as a small drop or bubble approaches a fluid‐fluid interface

Abstract

AbstractWhen 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.