COALESCENCE BETWEEN 2 SMALL BUBBLES OR DROPS

When two small drops or bubbles approach one another, a dimpled thin liquid film is formed between them. A model is developed for the dynamics of the thinning film in which both London-van der Waals and electrostatic double layer forces are recognized. The model predicts the coalescence time, which is the time required for the thinning and rupture of the liquid film, given only the radii of the drops and the required physical properties of the fluids and interfaces. In the absence of the electrostatic double layer forces, a more general expression is derived for the coalescence time. The predicted result is in good agreement with previous experimental results. © 1994 Academic Press, Inc.