Velocity Field of Thermocapillary Convection in High-Temperature Oxide Solution

We have investigated experimentally and theoretically the thermocapillary convective flow phenomena in a loop-shaped Pt wire heater of KNbO 3 (20 wt.%) and Li 2 B 4 O 7 solutions. Optical evaluations in connection with thermocouple measurements made it possible to get a new type of thermocapillary convective flow in the considered system. To study the kinematical behaviour of thermocapillary convection, we have measured the stream flow velocities. In a theoretical analysis, the flow velocity due to the thermocapillary effect alone was estimated by balancing the surface tension forces by viscous forces. The velocity distribution in the solution near the margin of the heater was obtained, which is in agreement with the experimental result.