THEORY OF HYDRODYNAMIC CONVECTION IN SOAP FILMS

We propose a hydrodynamic theory for gravity-driven convection in vert ical mobile soap films. Under steady-state conditions the equations re duce to the classical theory of film drainage and pull-out. We demonst rate that the steady-state film profile for drainage can be unstable a gainst lateral convection. The unstable mode - which is localized near the film border - is found to incorporate the physical characteristic s of the ''marginal regeneration'' phenomenology proposed by Mysels. W e discuss the mathematical relationship between soap film convection a nd Rayleigh-Benard convection in thermal cells and suggest experiments to test the analogy.