Taketoshi Hibiya

DIRECT OBSERVATION OF MARANGONI CONVECTION-INDUCED OSCILLATION AT SILICON MELT SURFACE

Marangoni convection-induced oscillation at the molten silicon surface of a half-zone liquid column was directly observed using real-time moire phase-shift interferometry. The oscillation frequency was analyzed by applying the Fourier transformation to the data of relative displacement versus time relationship of the melt surface. Several peaks of oscillation frequencies were observed at 0.5–5 Hz, being higher than the frequencies at 0.1–0.3 Hz observed in the previous studies by the temperature measurement using thermocouples and the x-ray flow visualization technique.

Coriolis Effect on Heat Transfer Experiment using Hot-Wire Technique on Centrifuge

A transient hot-wire technique was applied to examine the influence of the Coriolis effect on heat transfer on a centrifuge. A thermal conductivity measurement facility, once flown on board the TEXUS-24 rocket, was set on the 7.25 m rotating arm of the centrifuge. The temperature increase of the sensing wire, which was on a solid state substrate immersed in mercury, depended not only on input power and rotational acceleration but also on the orientation of the specimen. The temperature increase was affected by the Coriolis force, depending on the orientation: enhancement or suppression of heat transfer from the wire by convection.

Observation of surface oscillation in a molten silicon column using moire interferometry

Surface oscillation due to oscillatory Marangoni flow in a liquid bridge of molten silicon was observed using phase- shift interferometry. The molten silicon surface was described by phase-distribution profiles with a sampling rate of 30 Hz. From the phase-distribution profiles, we analyzed the oscillation of the radial displacement, axial gradient, and azimuthal gradient of the molten silicon surface. The oscillation of the radial displacement, axial gradient showed an in-phase relationship. However, in-phase oscillation was not observed between the radial displacement and the azimuthal gradient. Marangoni frequencies was observed at 0.1 to 5 Hz in which the frequencies higher than 1Hz had not previously been observed by conventional methods. We also found eigenfrequencies of the liquid bridge at 8.8Hz and 11.5Hz.