INFLUENCE OF SURFACE FORCES ON HYDRODYNAMICS OF WETTING

It is well known that properties of thin liquid films deviate from tho se of a bulk liquid. Disjoining pressure was introduced by Derjaguin t o describe thin liquid film behavior. The motion of a long oil drop or bubble under the action of an imposed pressure difference in a thin c apillary filled with another immiscible liquid is investigated theoret ically, taking into account the action of disjoining pressure. The vel ocity of the drop motion as a function of the pressure difference and the thickness of the film intervening between the drop and the capilla ry walls are calculated. The solution obtained coincides with Brethert on's equation at high velocities and deviates substantially at low vel ocities, which is a manifestation of disjoining pressure action in the thin film. In the same way, a problem concerning the thickness of a t hin liquid film covering a thin solid thread drawing out from a liquid container is considered. The thickness of the film is calculated as a function of the thread velocity. The theoretical results obtained are in good agreement with known experimental data.