Regular surface patterns on reyleigh-taylor and marangoni unstable evaporating films

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.Thin volatile Newtonian liquid films with a free surface on the underside of a cooled horizontal substrate are studied theoretically and numerically. We show that if the fluid is initially in equilibrium with its own vapor in the gas phase below, regular surface patterns in the form of long­wave hexagons having a well defined lateral length scale are observed. This is in sharp contrast to the case with­ out evaporation where rupture or coarsening to larger and larger patterns is seen in the long time limit. In this way, evaporation could be used for regular structuring of the film surface. The influence of a temperature dependent surface tension (Marangoni effect) is included as well, where special emphasis is layed on the S(}-called anomalous Marangoni ef­fect. In this case a parameter region where stripes should occur is found by means of a weakly non-linear analysis.