Thermal-solutal capillary convection in binary mixture liquid bridge with various aspect ratios under microgravity

Abstract

A numerical simulation is performed to investigate the thermal–solutal capillary convection in binary mixture liquid bridges with different aspect ratios (Ar) under microgravity. The open source software OpenFOAM with implemented Thermal-solutal capillary force code was used. The volume of fluid (VOF) method is used to capture small deformations on the free surface of liquid bridges, and ground experiments are performed to verify the accuracy of the code used. The results reveal that the flow cell shows flow characteristics of mutual intrusion during the generated stage and the degree of change in the shape of the free surface is calculated. Thermocapillary convection is generated at the first stage; subsequently, with the diffusion of solutes in liquid bridges, thermal–solutal capillary convection occurs. The direction of the convective vortex changes from clockwise to counterclockwise because the direction of the solutocapillary force is opposite to that of the thermocapillary force. The concepts of strong and weak convection zones are proposed herein. The weak convection zone is mainly located in the center of the liquid bridge, whereas the strong one near the interface. The extent of the strong convection zone stabilizes as the Ar of the liquid bridge increases beyond 1.