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

When a solid surface makes contact with a fluid-fluid interface, a three-ph ase contact line is formed. This contact line may move along the surface, d riven 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, t he formation and unsteady motion of contact lines has not. The process of c ontact-line formation is of obvious interest in any physical situation wher e contact lines exist. In order to study the formation and motion of contac t lines we have analysed a particular model problem: the interaction of an initially flat interface between two inviscid fluids with a thin, semi-infi nite, flat plate. We extend the results obtained by Billingham and King (J. Fluid Mech 296 1995), where this problem was studied for the case of norma l incidence, to incidence at an arbitrary initial angle.