Oscillatory thermocapillary flow in cylindrical columns of high Prandtl number fluids

Oscillatory thermocapillary flow of high Prandtl number fluids in the half-zone configuration is investigated experimentally, Small zones (diameter less than or equal to 3 mm) are used to minimize the effects of buoyancy and gravity on the oscillation phenomenon. The effects of buoyancy and zone shape on the phenomenon are carefully assessed. The conditions for the onset of oscillations are studied under various conditions and for various zone shapes to End the dimensionless parameter(s) to specify the onset. The present data are compared with available data taken in microgravity. It is shown that for a given zone shape and fluid, the onset conditions in the absence of buoyancy cannot be specified by the Marangoni number alone.