Oscillatory thermocapillary flow in encapsulated liquid column

The thermocapillary flow in a half zone model of an encapsulated liquid col umn was studied experimentally. The encapsulated liquid column was formed s uccessfully with the use of two immiscible liquids, the silicone oil and Fl uorinart. The thermocapillary convection was induced in the inner and outer columns by temperature difference imposed between top and bottom disks. Wi th the increase of the temperature difference, the flow exhibited the trans ition from axisymmetric steady to nonaxisymmetric oscillatory flow. The osc illation started in the lower viscosity fluid and influenced the higher one . The critical Marangoni number was determined for different combinations o f inner and outer column liquids. If the lower viscosity fluid was encapsul ated with the higher one, the start of the oscillation was significantly re tarded compared to the transition of the single column. (C) 2001 American I nstitute of Physics.