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ISSN Online: 2377-424X

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

Experimental study of oscillatory thermocapillary convection around a bubble under variable gravity. Flow and heat transfer using optical and thermal methods

Get access (open in a dialog) DOI: 10.1615/IHTC12.2560
6 pages

Résumé

Thermocapillary convection around a single air bubble introduced under a heated horizontal wall in a silicone oil layer is investigated experimentally. For liquids with a low Prandtl number, different states of thermocapillary convection exist. When a critical threshold is exceeded, an oscillatory state follows the steady one. Experiments are performed under normal gravity and microgravity conditions. Because of standards and experimental constraints on board an Airbus A300, two kinds of test chamber are used. The initially axisymmetrical flow in the shape of a roll around the bubble becomes time dependent. By means of a completely transparent test chamber, the periodic 3D spaciotemporal structure of the thermocapillary convection is visualized by shadowgraphy and tracer particles. The periodic structures with a wave number equal to 2 and 3 are shown. The influence of the bubble size, the temperature gradient and the gravity level on heat transfer induced by the thermocapillary convection are studied. Under reduced gravity, the thermocapillary roll develops down to the bottom of the test chamber and heat transfers increase.