Study on Bi_(12)SiO_(20) Melt Marangoni Convection

Schilren technique coupling differential interferential microscope was employed to insitu observation high temperature Bi12SiO20 melt Marangoni convection. The bifurcation of oscillatory convection was also observed in this experiment and the oscillatory frequency was obtained as 5~7Hz. In the steady convection stage, the flow configuration appears as fish-like shape which comprises of a main-trunk and two branches. The width of the main-trunk decreases with temperature rising. Meanwhile, along the main-trunk two darker color regions appear symmetrically. The distance between them becomes, narrower gradually and crossed together at last. This is the critical point for the transition to oscillatory convection. The critical Marangoni number Mac 22433 experimentally obtained for Bi12SiO20 melt, agrees with a theoretical speculation Mac=2884Pr0.638 for high Prandtl number melt.