Numerical Simulation of the Effect of Free Surface Shape on Marangoni Convection in a Liquid Film Sustained in a Circular Ring with Different Prandtl Numbers

Abstract

In 2003 NASA astronaut Dr. D. Pettit conducted thermocapillary experiments in a thin water film (Prandtｌ number; Pr = 7) sustained in a circular ring onboard the International Space Station (ISS). When a section of the ring was heated, a thermocapillary flow developed from the cold region towards the hotter region. This unusual flow phenomenon (being from cold to hot) was explained by the dependency of free surface shape on the flow pattern observed in the film. However, the dependency of flow behavior on the Prandtl number was not investigated previously. Motivated by the wide range of applications of the low-Prandtl-number liquids, numerical simulations for the flow phenomena observed in the films of different shapes and Prandtl numbers were performed under zero gravity. Results have shown that in the case of low-Prandtl-number film although the flow direction remained the same, the flow velocity increased significantly. This interesting phenomenon is explained by means of the temperature gradient in the film in the y- (vertical) and-θ(circumferential) directions.