Numerical Simulation of Self-Induced Thermocapillary Flow for Non-Uniform Evaporating Meniscus in Capillary Tubes

A computational model was developed to describe self-induced thermocapillary convection for non-uniform evaporating meniscus in vertical capillary tubes, which was filled with ethanol, methanol or water. The diameters of capillary tubes ranged from 100 μm to 1000 μm. The direct numerical simulation using control volume approximation was used to investigate the thermocapillary flow in the liquid phase. Three types of distribution of the heat flux along the liquid-vapor meniscus interface were investigated for various Marangoni numbers, to characterize the flow pattern under conditions close to realistic operating parameters. The simulation shows that the flow pattern depends on the thermal boundary condition on the liquid-vapor meniscus interface and the Marangoni number, but is very insensitive to the buoyancy force for thermocapillary convection for non-uniform evaporating meniscus in the capillary tube with the radius r_o<500μm.