Numerical simulation of moving contact line problems using a volume-of-fluid method

Moving contact lines are implemented in a volume-of-fluid scheme with piece wise linear interface construction. Interfacial tension is treated as a con tinuous body force, computed from numerical derivatives of a smoothed volum e-of-fluid function. Two methods for implementing the contact angle conditi on are investigated. The first extrapolates the volume-of-fluid function be yond the flow domain, on the basis of the condition that its gradient is pe rpendicular to the interface and that the normal to the interface at the wa ll is determined by the contact angle. The second method treats the problem as a three-phase situation and mimics the classical argument of Young. It is found that the latter approach introduces an artificial localized flow, and the extrapolation method is preferable. Slip is a crucial factor in the spreading of contact lines; the numerical method introduces slip at the di screte level, effectively introducing a slip length on the order of the mes h size. (C) 2001 Academic Press.