ISSN Online: 2377-424X
International Heat Transfer Conference 12
Experimental study of oscillatory thermocapillary convection around a bubble under variable gravity. Flow and heat transfer using optical and thermal methods
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.