EXTRAPOLATED DYNAMIC CONTACT-ANGLE AND VISCOUS DEFORMATION OF A STEADY MOVING MENISCUS AT A VERTICAL FLAT WALL

The profile of a steady meniscus at a flat wall vertically withdrawn f rom a liquid is considered. The extrapolated dynamic contact angle, th eta(ext), serving as a boundary condition of Laplace equation for the quasi-static part of the fluid interface is introduced and its depende nce on contact line velocity, viscosity, surface tension, density of t he liquid, and static wettability of the solid is obtained and numeric ally analyzed. The thickness of the hydrodynamic deformation of the me niscus, h(qs), is also related to these properties and a nonmonotonous dependence of this thickness on contact line velocity is found. Two d ifferent dynamic behaviors of the contact line, constant and velocity- dependent actual dynamic contact angle, are considered, and a strong d ifference between the corresponding dependences of theta(ext) and h(qs ) on contact line velocity is established. If the other properties of the system remain the same, the velocity dependence of the actual dyna mic angle makes the extrapolated dynamic angle decrease from the stati c value to 0 degrees much faster and strongly reduces the hydrodynamic deformation of the moving meniscus.