Theory of hydrodynamic convection in soap films

We propose a hydrodynamic theory for gravity-driven convection in vertical mobile soap films. Under steady-state conditions the equations reduce to the classical theory of film drainage and pull-out. We demonstrate that the steady-state film profile for drainage can be unstable against lateral convection. The unstable mode — which is localized near the film border — is found to incorporate the physical characteristics of the “marginal regeneration” phenomenology proposed by Mysels. We discuss the mathematical relationship between soap film convection and Rayleigh-Benard convection in thermal cells and suggest experiments to test the analogy