Surface deformation and film corrugation during drying of polymer solutions induced by Marangoni phenomena

摘要

Solutal Marangoni phenomena occurring during drying of polymer solutions are investigated through numerical simulations. Benard-Marangoni convection and free surface deformation are considered, taking into account the strong dependence of viscosity with solute concentration. Simulations show that free surface deformation which is resisted by capillary pressure reaches an overall magnitude that is proportional to the capillary number. Decreasing Ca also inhibits the interface deformation by favoring the formation of plumes that enhance mixing of the solute. For the range of capillary numbers corresponding to experiments, free surface deformation is not significant. However Benard-Marangoni convection induces non uniformity of solute concentration and the varying viscosity leads to accumulation of solute at the periphery of convective cells that is observed up to the end of drying. Though simulations have been performed with dimensionless numbers significantly milder than the experimental ones, they are in agreement with experimental observations presented here and in the literature, suggesting that wrinkles may be viewed as the signature of Benard-Marangoni convection.