We study nonlinear effects on film rupture by investigating the stability of a viscous free film to finite amplitude disturbances. Until now, theoretical results were obtained through a linear stability analysis for infinitesimal perturbations, which is only valid for a short time since disturbances grow to finite size at rupture. The liquid film considered is uncharged, nondraining, and laterally unbounded. The dynamics of the film is described by the Navierndash;Stokes equations where attractive van der Waals forces are operative, with suitable boundary conditions at the two surfaces (in the particular case of tangentially immobile surfaces). A nonlinear evolution equation describing the variation of the film thickness along the lateral space dimension, is derived for the squeezing mode which is characterized by symmetrical surface waves. This highly nonlinear partial differential equation is solved numerically and rupture characteristics are predicted and compared to experiments. It is shown that the nonlinearities significantly accelerate the rupture process.
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