Enhancement of the drainage of non-Newtonian liquid films by oscillation

Abstract

The flow of thin liquid films down an oscillating vertical surface is investigated both theoretically and experimentally for Newtonian and non-Newtonian liquids. The effects of the oscillation are explored analytically for Newtonian and linear viscoelastic liquids, and numerically for a generalized Newtonian liquid. The oscillatory motion has no net effect on the drainage of Newtonian and linear viscoelastic liquids, but enhancement is predicted for shear-dependent liquids. A gravimetric experiment is developed to check the theoretical predictions. The experiment enables the mass of liquid remaining on an oscillating glass tile to be monitored as a function of time. Good quantitative agreement between theory and experiments is shown for Newtonian liquids. For shear-thinning non-Newtonian liquids the experiments confirm that the predicted enhancement in the drainage occurs, in qualitative agreement with theory.