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

In this paper, a computational fluid dynamics (CFD) approach is used to analyze and numerically present the droplet movement in both stagnant and vibrated liquid in a rotating cylinder. The Ansys Fluent commercial software package is used to solve the governing continuum conservation equations for two-phase flow. The volume of fluid (VOF) method is used to track the liquid/liquid interface. The inherent velocity of droplets decreases with increasing Marangoni number, in agreement with previous space onboard experimental findings that have been documented in literature. Complex behaviors of droplets in zero gravity were observed due to small host fluid vibration and rotational motion, which are neglected in the presence of gravity. Therefore, the impact of varying vibration amplitude as well as angular velocity on bubble migration is presented. It has been found that thermocapillary migration slows down with high vibration amplitude (A), when the fluid is vibrating. For a static liquid inside a rotating cylinder, the velocity of thermocapillary droplet migration decreases with the angular velocity increase. Temperature gradient (∇T) increment also increases the droplet's migration speed inside the vibrating fluid and a rotating cylinder of different Marangoni numbers (Ma_T). A flow pattern figure that illustrates the actual flow behind each modification is included with every result.