The moving contact line between two wedges of fluid on a flat plate

Abstract

When a solid surface makes contact with a fluid-fluid interface, a three-phase contact line is formed. This contact line may move along the surface, driven by both the external fluid flow and the thermodynamically-determined contact angle that the fluid-fluid interface makes with the solid surface. Although the steady motion of contact lines has been studied extensively, the formation and unsteady motion of contact lines has not. The process of contact-line formation is of obvious interest in any physical situation where contact lines exist. In order to study the formation and motion of contact lines we have analysed a particular model problem: the interaction of an initially flat interface between two inviscid fluids with a thin, semi-infinite, flat plate. We extend the results obtained by Billingham and King, where this problem was studied for the case of normal incidence, to incidence at an arbitrary initial angle