The Interfacial Physics Group

Carnegie Mellon University, Department of Physics

Thin Film and Intertial Effects on the Hydrodynamics Near Moving Contact Lines

by Kroum Stoev



Intricate and fascinating physics control how liquids spread on solids. Wetting is also of major importance in many technological processes. Dynamic wetting is an intrisically complex problem with difficulties arising due to the unique hydrodynamics which must operate in the microscopic region near the contact line and control the macroscipoc streading of a liquid. Models and experiments on wet and dry substrates exist, but all are in the slow flow regime where viscous forces very near the contact line are especially important. In this thesis, we have moved to new regimes where thin films exist near the moving contact line and hwere inertia is becomiing important. We examine the hydrodynmics using video microscopy and digital image analysis to measure the liquid/vapor interface shape in a microscopic region near the contact line. We have developed and experminatally verified an analytical model describing the interface shape close to the moving contact line in the presence of a film. We have observed that molecular scale and micron scale films have different effects on the hydrodynamics near the contact line. We have also investigated the effects of inertia on the hydrodynamics close to contact lines. We look at the case wehre steady state motion of the contact line leads to moderate Reynolds numbers. We have established that inertia decreases the dynamic curvature and the apparent contact angle as the Reynolds number increases.