Effects of gravity on the thermo-hydrodynamics of moving contact lines

Abstract

In this paper, we demonstrate the effects of gravity on the interfacial thermo-hydrodynamics as modulated by the patterned wettability gradients placed on the surfaces of a narrow fluidic channel. We investigate the dynamics of contact line motion of two-component incompressible immiscible liquid mixtures under the framework of a thermodynamically consistent phase field model. We validate our model with the experimental results available in the literature in the purview of thermocapillary-actuated microscale transport. We show that the gravity-induced forces in the presence of the thermocapillarity effect play a unique role on the interfacial dynamics at small scales, leading to a uniform movement of the interface in the channel, and offer a greater degree of controllability in the filling/wetting rate in the capillary. We show that the change in patch width, placed on the walls of the channel, leads to a change in the filling dynamics into the capillary. Also, we investigate the rate of different dissipations during the movement of the contact line along the channel and show that the kinetic energy modulated dissipation provides maximum energy to the motion of the contact line.