A Model for the Dynamics of Partial Wetting

Abstract

A model is proposed for the dynamics of spreading of a liquid drop under the action of capillary forces in the case of partial wetting. Deviation from the spherical cap profile is taken into account. The spreading kinetics is obtained using a dynamic contact angle boundary condition in which the velocity of the contact line is given as a function of the dynamic contact angle and a cut off of molecular size below which the continuum theory breaks down. Results are found to be in very good agreement with published experimental data even at high dynamic contact angles, well beyond the range of applicability of the lubrication theory. Differences between the spreading and dewetting cases are discussed. Further investigation is needed to treat the dewetting case.