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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Interaction among natural convections in two immiscible liquid layers subject to a horizontal temperature gradient

Get access (open in a dialog) DOI: 10.1615/IHTC12.3660
6 pages

Résumé

Marangoni convection, driven by an interfacial instability due to a surface tension gradient, has become a large problem in the crystal growth. To suppress and control the convection is important for the material processing. Especially in the crystal growth by LEC technique, in which the melt is encapsulated with an immiscible medium, Marangoni convection can occur on the liquid-liquid interface and on the gas-liquid free surface. On the ground, buoyancy driven convection also affects the flow. In the LEC crystal growth process, the oscillating flow in the encapsulant should affect the temperature distribution in it and/or in melt. The position of crystallization, which was important for controlling crystal growth process, might be affected. Many researchers have tried to simulate the flow mentioned above. However, there is no paper with good experiments. In the present paper, experiments were carried out with a double liquid layer in an open-boat system and in an enclosed system. Flow in a cavity subject to a horizontal temperature gradient was observed. An interactive flow near the interface was measured by using PIV technique. The measured flow field seemed to agree enough with the numerical prediction. More detailed observation was made about the flow in an upside layer with a free surface, which showed more complex and interesting phenomena because of the interactions of natural convections. The velocity was always largest within a thin layer of about 2 mm near the free surface. With increasing Ra number, the circulating flow branched into two. The shearing vortex was observed near the stagnant region between the interface and the hot wall. Oscillatory flow of the branched circulating flow was observed. It might be induced by the instability of their interaction. In addition, we succeeded to measure the free surface fluctuation with several dominant frequencies.