A Three-Dimensional Simulation of Thermocapillary Flow in a Circular Thin Liquid Film under Zero Gravity

Abstract

Dr. D. Pettit, a NASA Astronaut, carried out a thermocapillary flow experiment in a thin water film on-board the International Space Station (ISS) in 2003. The thin water film containing milk powder tracers was formed in a stainless-steel wire ring. The heating of a section of the ring by a soldering iron induced a thermocapillary flow in the water film. This flow was towards the heated part of the ring (outward flow); in the opposite direction (from hot to cold) to the ordinary thermocapillary flows observed in a liquid bridge and a liquid film. To shed light on the discrepancy observed between the space experiment and the ordinary thermocapillary flow, we have carried out a three-dimensional numerical simulation study. In the simulation we have also included the effect of meniscus shape. The simulation results showed that the meniscus shape determines the flow direction. Its consideration in the simulation also led to the prediction of an outward flow (from center to the heated part of the ring) in the water film as observed in the space experiment of Dr. D. Pettit.