Effect of wall proximity on the lateral thermocapillary migration of droplet rising in a quiescent liquid

Abstract

A numerical study is performed to observe the effect of lateral wall proximity on the thermocapillary migration of a droplet. Three-dimensional simulations of the droplet with lateral wall proximity show that the droplet is pulled toward the wall for larger temperature gradients in the ambient and pushed away from the wall at smaller temperature gradients. Parametric studies carried out for migration of a droplet in the vicinity of a wall in a two-dimensional domain show that the droplet behavior is similar to the three-dimensional domain. At different temperature gradients, the final lateral distance of the droplet from the wall does not vary monotonically. The interaction of the temperature field at the leading and trailing ends of the migrating droplet with the wall explains the observed behavior. An extensive parametric study is performed to understand the effect of the Marangoni number, Reynolds number, and property ratios on droplet migration near the wall. Variation in each parameter influences the evolution of temperature both within the droplet and in the ambient fluid. The asymmetric interfacial temperature variation due to the asymmetric evolution of internal circulation within the droplet is correlated with the lateral migration of the droplet. The observations made in the present work reveal physical mechanisms that influence the thermocapillary migration behavior of a droplet near a wall.