液柱内温度差マランゴニ対流の振動流に対する全周加熱制御

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A new scheme of active control was tested on nonlinear thermocapillary convection in a half-zone liquid bridge of a high Prandtl number fluid. In the half-zone method, two co-axial cylindrical rods hold a liquid bridge by surface tension. By applying a temperature difference between the rods, a thermocapillary flow is induced in the liquid bridge. The convection changes from a two-dimensional steady flow to a three-dimensional oscillatory one at a critical value of temperature difference or of Marangoni number. The control was realized by introducing concentric circular wire heater in order to heat round of the liquid bridge azimuthally. With this control scheme, one can suppress the oscillatory convection without minding the spatio-temporal fluctuation of the temperature over the free surface. The comparison between the present control scheme and the previous local heating by our group was conducted in terms of the time series of the surface temperature variations and the visualized flow field from the top. The experiment was conducted on a unit-aspect-ratio liquid bridge where the most unstable azimuthal mode had wavenumber 2 without control. The control with the present scheme achieved more significant attenuation of the temperature oscillation for a wider range of Marangoni number. The amplitude of the oscillation was able to be suppressed to a few percent of the initial value up to about 200 percent of the critical Marangoni number. The dependence of the control performance upon the position of the heater was investigated and found significant for both the control schemes. A mechanism of the stabilization from the oscillatory to the steady flow was examined. The stabilization is due to the reduction of the thermocapillary flow caused by the variation of the axial surface temperature distribution.
社団法人日本伝熱学会の論文
2006-04-01

液柱内温度差マランゴニ対流の振動流に対する全周加熱制御

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