Asymptotic behaviour of the thin film equation in bounded domains

We investigate the extinction behaviour of a fourth order degenerate diffus ion equation in a bounded domain, the model representing the flow of a visc ous fluid over edges at which zero contact angle conditions hold. The extin ction time may be finite or infinite and we distinguish between the two cas es by identification of appropriate similarity solutions. In certain cases, an unphysical mass increase may occur for early time and the solution may become negative; an appropriate remedy for this is noted. Numerical simulat ions supporting the analysis are included.