Effect of surface viscoelasticity on the film drainage and the interfacial mobility

The effect of the surface viscoelasticity on the drainage of the film between two gently colliding fluid particles is studied. The interfaces bounding the thin film are treated as deformable ones, which follow the surface analogous of the Upper Convected Maxwell model. The presence of the elastic forces on the interface is found to delay the viscous response of the interface, i.e., the interface behaves as inviscid for a certain duration before recovering the Newtonian behavior. The duration of this delay scales with the magnitude of the surface Weissenberg number, whereas the surface viscous forces determine the time at which the deviation from the inviscid behavior begins. This delay also indicates a shift in the tangential mobility of the interface with time during the drainage, as the inviscid and the Newtonian interfaces’ are the most mobile and the least mobile cases, respectively. Consequently, the coalescence time and behavior show a similar shift, yielding cases where the coalescence time estimated for the viscoelastic interface is significantly different than both the ones for the inviscid and the Newtonian interfaces.