Suppression of thermocapillary oscillations in sodium nitrate floating half-zones by high-frequency end-wall vibrations

Abstract

Experiments to suppress thermocapillary oscillations by using high-frequency end-wall vibrations were carried out in sodium nitrate floating half-zones. Such a half-zone is formed by melting one end of a vertically held sodium nitrate crystal rod in contact with a hot surface at the top. Thermocapillary convection occurs in the melt due to the imposed temperature gradient at the free surface. When this temperature gradient is large enough, steady thermocapillary convection becomes unstable, and thermocapillary oscillations occur. In such a context, the bottom end of the crystal rod was vibrated at a high frequency to generate a streaming flow in a direction opposite to that of thermocapillary convection. It is observed that by generating a sufficiently strong streaming flow, the thermocapillary oscillations can be quenched everywhere in the melt zone.