Thermocapillary migration of a self-rewetting droplet on an inclined surface: A phase-field simulation

TL;DR

This study uses phase-field lattice Boltzmann simulations to analyze how self-rewetting droplets move on inclined surfaces, revealing effects of Marangoni number, wettability, viscosity ratio, and inclination angle on droplet behavior.

Contribution

It introduces a phase-field lattice Boltzmann model to simulate self-rewetting droplet migration, highlighting the influence of multiple parameters on droplet dynamics.

Findings

Droplet speed increases with Marangoni number.

Droplets migrate towards higher surface energy on hydrophilic surfaces.

Viscosity ratio affects vortex formation inside the droplet.

Abstract

In this paper, we investigated the thermocapillary migration of a self-rewetting droplet on an inclined surface using a phase field based lattice Boltzmann method. Unlike the normal fluid whose surface tension decreases linearly with temperature, the self-rewetting fluid consider in the current work has a quadratic temperature dependence of surface tension with a well-defined minimum. we first explored the influence of the Marangoni number on droplet migration, and found that the droplet hardly deforms and migrates slowly when the Marangoni number is small. However, as the Marangoni number increases, the droplet begins to deform and elongate, and its migration speed increases. Subsequently, we studied the effect of surface wettability on droplet migration. The results show that the droplet migrate towards regions of higher surface energy on hydrophilic surfaces and in the opposite direction on hydrophobic surfaces. Furthermore, by varying the viscosity ratio and the inclination angle of the plate, we found that the droplet's migration speed decreases with an increase in the viscosity ratio. In particular, two vortices appear inside the droplet at a high viscosity ratio, whereas only one vortex is present at a low viscosity ratio.