Viscous flow separation caused by the Marangoni effect in competition with capillary flow

This letter provides an analytical model that describes the viscous flow separation in a drying thin polymer solution film. While conventional flow separation occurs due to an adverse pressure gradient opposing fluid inertia, here we show that flow separation can also be caused by the Marangoni effect in an evaporation-driven creeping flow. The flow separation behavior strongly depends on the surface tension distribution and the interface profile. Viscous flow separation adds to the current understanding of flow physics during the drying of thin films, in addition to the well-known capillary transport and the Marangoni effect. (C) 2015 AIP Publishing LLC.