Investiagtion of Free Surface Heat Transfer Effect and Oscillation Mechanisms for Thermocapillary Flow of High Prandtl Number Fluid(Marangoni Convection Modeling Research, 2003-2004)

概要

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The effect of free surface heat transfer on oscillatory thermocapillary fl ow in liquid bridges of high Prandtl number (Pr) fl uids is investigated experimentally as well as numerically. It has been found that the critical condition is very sensitive to the free surface heat transfer under certain conditions but relatively insensitive under other conditions. In this work it is shown that this sensitivity difference may be related to the difference in the oscillation mechanism. Several oscillation mechanisms have been proposed in the past for oscillatory thermocapillary fl ows in liquid bridges of high Prandtl fl uids, mainly hydrothermal wave type instability and a non-linear mechanism involving dynamic free surface deformation. It is discussed here that the range of Marangoni number, where the fl ow is found to become oscillatory in many experiments for high Pr fl uids, is too low for the fl ow to become unstable by the hydrothermal wave instability mechanism, or any linear instability mechanism. Instead, we need non-linear mechanisms where the driving force is altered continuously by some means. In order to get this conclusion, our past work is summarized and some new results are presented herein.
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