Mesoscopic Analysis of Dynamic Droplet Behavior on Wetted Flat and Grooved Surface for Low Viscosity Ratio

Abstract

In the present study, the interfacial dynamics of displacement of three-dimensional spherical droplet on a rectangular microchannel wall considering wetting effects are studied. The two-phase lattice Boltzmann Shan−Chen model is used to explore the physics. The main focus of this study is to analyze the effect of wettability, low viscosity ratio, and capillary number on the displacement of spherical droplet subjected to gravitational force on flat as well as grooved surface of the channel wall. The hydrophobic and hydrophilic natures of wettabilities on wall surface are considered to study for viscosity ratio, M≤1. The results are presented in the form of temporal evolution of wetted length and wetted area for combined viscosity ratios and wettability scenario. In the present study, it is observed that in dynamic droplet displacement, the viscosity ratio and the capillary number play a significant role. It is found that as the viscosity ratio increases, both the wetted area and the wetted length increase and decrease in the case of hydrophilic and hydrophobic wettable walls, respectively. The groove area on the vertical wall tries to entrap fraction of droplet fluid in case of hydrophilic surface of the vertical wall, whereas in hydrophobic case, droplet moves past the groove without entrapment.