Influence of Temperature Gradients and Fluid Vibrations on the Thermocapillary Droplet Behavior in a Rotating Cylinder

Abstract

When a fluid moves from lower to higher surface tension regions, its bubble or droplet moves in the direction of the temperature gradient (∇T), a process known as Marangoni flow occurs. In this paper, the drop movement in both stagnant and vibrated liquid in a rotating cylinder is analyzed and numerically presented using a computational fluid dynamics (CFD) approach. For two-phase flow, the governing continuum conservation equations are solved using the commercial program Ansys-Fluent. The Volume of Fluid (VOF) method has been found to be a useful research tool for studying multiphase interaction. It tracks the liquid/liquid interface in 2D and 3D domains. As the Marangoni number increases, the inherent velocity of drops decreases, which is consistent with earlier space onboard experimental findings that have been documented in the literature. This work revealed the complex behavior of droplets in zero gravity, where some neglected forces, such as rotational motion and host fluid vibration, that vanish in the presence of gravity, are the main source of the observed behavior. It was discovered that the thermocapillary droplet migration, which was insignificant in the presence of gravity, was significantly influenced by the small frequency amplitude (Am), which decreases with an increase in it. The study also showed that, in a static liquid inside a rotating cylinder, the velocity of thermocapillary droplet migration decreased. Up until this effect vanishes with increasing temperature gradient, increasing the temperature gradient (∇T) also increases the migration speed of the droplet inside the vibrating fluid and a rotating cylinder of different number of Marangoni (Ma