MOVING CONTACT LINE DYNAMICS ON CURVED SUBSTRATES

Abstract

Numerical simulations of moving three-phase contact line on curved substrates are performed in scenarios without any splashing or rebounding after liquid impact. While velocity-based dynamic contact angle models have been used previously, a force-based approach that closely relates dynamic contact angle to underlying flow physics has not been implemented for curved surfaces. Here, a force-based model is implemented, where dynamic contact angle is adjusted by wetting force at contact line. The magnitude and direction of wetting force is calculated for different geometries after computing dynamic contact angle with respect to equilibrium contact angle, while considering curvature of substrate during contact line motion. The resolved components of wetting force are included as source terms in radial and axial momentum equations, for which a sign convention is derived for different configurations. The overall algorithm for wetting force is implemented using user-defined routines within the framework of an existing CFD solver employing volume of fluid method. Adaptive mesh refinement is also used near the interface due to intensive nature of the computations. The model is used to simulate droplet impact on convex and concave spherical surfaces, and conical surface along with water entry of a spherical ball. The effect of curvature and impact velocity on contact line motion over convex spherical surface is studied, while the role of contact angle for different surfaces is also examined. The simulations capture the temporal evolution of dynamic contact angle closely based on the underlying physical mechanisms, and deviations from the specified equilibrium contact angle values are also discussed.