Conditions for the onset of temperature oscillations in a simulated floating-zone configuration

The floating-zone method for crystal growth is studied in simulated low-gravity conditions by suspending a drop of fluid vertically between two circular rods and heating the upper rod with a heater. Flow and temperature oscillations are observed under certain conditions. The temperature oscillation level and the oscillation frequency are measured against the Marangoni number for several aspect ratios using hexadecane and Fluorinert as the test fluids. It is observed that, contrary to what has been believed, the Marangoni number is not the proper parameter to describe the onset of oscillation.