2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150476Centre manifold techniques are used to derive rationally a description of the dynamics of thin films of fluid. The derived model is based on the free-surface $η(x,t)$ and the vertically averaged horizontal velocity $\avu(x,t)$. The approach appears to converge well and has significant differences from conventional depth-averaged models.170K postscript, 7 pages Keywords: long-wave approximation, thin fluid film, low-dimensional model, centre manifoldChaotic Dynamicstext