HYDRODYNAMIC STABILITY OF THIN FILMS

The study of the stability of thin liquid films is of interest from a practical and scientific point of view. Study of the stability of thin free liquid films are of importance for an understanding of colloid systems such as foams and emulsions.;The object of the present research is as follows: (i) Formulate the dynamics of the thin film using the Navier-Stokes equations augmented by body forces describing London/van der Waals attractions and double-layer repulsion forces. (ii) Examine the resulting nonlinear evolution equation for h(x,t), the film thickness. (iii) The evolution equation (a strongly nonlinear partial differential equation is difficult to analyze, even numerically. An asymptotic limit of vanishing capillary number is used to obtain a "large surface tension" approximation to the evolution equation. (iv) The simplified evolution equation (neglecting double-layer forces) is then solved numerically. An aim of the research is to see how the nonlinear evolution affects the time to rupture and the spatial structure of the developing layer.;This dissertation presents the results of research on the nonlinear stability of thin films to finite amplitude disturbances. Previous work has been restricted to the linear stability of thin films to infinitesimal disturbances.