Spreading of Water: Condensation Effects

Although the macroscopic, bulk behavior of liquids wetting (or dewetting) can be adequately explained by viscous flow, the intricate details near the solid/liquid/fluid triple line (TL) are still not totally appreciated.These two aspects correspond to the bases of the hydrodynamic approach and of the molecular kinetics approach, respectively, to explain spreading. We have suggested a complementary model to that of molecular kinetics, based on the modified curvature of a dynamic, wetting meniscus near the TL, which leads to local condensation of vapor from the surrounding atmosphere, further contributing to motion. An earlier paper dealt with liquids whose thin film behavior (i.e., near the TL) is dominated by long-range van der Waals forces. Here, we turn our attention to the spreading of water. Basic equations are modified to allow for non-negligible meniscus slope and then applied to a model for water, consisting of two different, thickness dependent, disjoining pressure isotherms.