MOVING CONTACT LINES IN SLENDER FLUID WEDGES

A wedge of fluid is held at rest with its upper edge a free surface and its lower edge in contact with a solid boundary. If the wedge angle of this static system differs from the contact angle of the fluid-solid combination then an adjustment of the wedge angle to a constant dynamic contact angle results when the system is released from rest. The induced motion in the fluid is of a self-similar type and is sustained by surface-tension forces. In the case of a slender fluid wedge of angle epsilon whose dynamic contact angle is O(epsilon) the rather complicated equations of motion can be reduced by a perturbation procedure to a novel two-point boundary-value problem. Asymptotic and numerical solutions to this are found and the displacement of the contact point and the free surface are investigated for a variety of parameter values.