Abstract:

The coalescence process between two small drops of different sizes in pure liquid-liquid dispersions has been studied. When two small drops approach each other, a dimpled thin liquid film is formed between them. A model is developed for the dynamics of the thinning film in which the influence of London-van der Waals force has been considered. The model predicts that the coalescence time, which is the time required for the thinning and rupture of the liquid film, can be expressed only by the radii of the drops and the physical properties of two phases.  A wide range of viscosity ratio of dispersed phase to continuous phase is examined, so that the theoretical prediction is also valid for bubble coalescence in a liquid. It is shown that the coalescence times are strongly dependent on the viscosity ratios. The prediction results are in good agreement with the previous experimental results.

Key words: Drop, Thin liquid film, Coalescence time