FLOW AND HEAT TRANSFER CHARACTERISTICS OF THERMOCAPILLARY CONVECTION OF HIGH PRANDTL NUMBER FLUID IN CYLINDRICAL BRIDGE
K. Nishino1, E. A. Matida1 and S. Yoda2
1Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
2National Space Development Agency of Japan, 2-1-1 Sengen, Tsukuba City, 305-8505,
Japan
The onset of oscillation of thermocapillary convection (or Marangoni convection) in
cylindrical liquid bridge has been a target of extensive studies from view points not only of
the material processing in microgravity but also of the fundamental instability mechanism in
this unique convection. The uniqueness lies in the facts (1) that the convection is driven by
the surface tension gradient present along the liquid-gas interface, (2) that there is a strong
coupling between fluid motion and fluid temperature, and (3) that the liquid surface may be
deformed statically and dynamically. The last feature, particularly the dynamic surface
deformation (DSD, hereafter), has not been paid enough attention so far even though some
recent studies (e.g., Masud et al. 1997 and Kamotani & Ostrach 1998) have pointed out
possible roles of DSD in the mechanism of onset of oscillation.
This report describes the results gained in experimental work done at Heat Transfer
Laboratory of Yokohama National University in the period from April 2000 through March
2001. The work consists of (1) measurement of static surface deformation caused by the
onset of convection, (2) simultaneous observation of flow patterns and DSDs of oscillatory
convection, and (3) evaluation of heat loss from the free liquid surface. All of these are
aiming at obtaining direct experimental clues that support the importance of DSD in the onset
of oscillation of thermocapillary convection in cylindrical liquid bridge.
- Full Report :PDF File (1MB)
