713 Correlation between Dynamic Surface Deformations and Surface Temperature Fluctuations of Marangoni Convection in a Liquid Bridge
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Some recent studies (e.g., Kamotani & Ostrach 1998) on the onset of oscillation of thermocapillary flow (Marangoni convection) of a simulated half-floating zone have shown that the onset is not determined by the Marangoni number alone and dynamic surface deformation is conjectured to play an important role in the onset mechanisms. The present paper is aiming at obtaining a direct clue to the physical significance of the dynamic surface deformation by performing a series of simultaneous measurements of surface temperature oscillation and dynamic surface deformation. An IR camera with a framing rate of 30 fps is used to measure unsteady temperature distributions on the surface of liquid bridge after the onset of oscillation. Simultaneously, the dynamic surface deformation along an edge of the liquid bridge is measured by a microscopic imaging technique with a spatial resolution of 0.37 μm and a temporal resolution of 30 Hz. Their synchronous operation permits measurement of phase relationship between surface temperature oscillation and dynamic surface deformation. It is revealed that (1) the surface temperature exhibits a rotational oscillation of mode 1 with a period of 1.2 s under the present conditions (d=5 mm, Ar=0.5, V/V_0=0.62 and ΔT=ΔT_c+1 K), (2) there is about 180 deg phase difference between surface temperature oscillation and dynamic surface deformation, and (3) the rotational surface temperature oscillation has a spatial distribution inclined to the axis of liquid bridge in such a way that the phase of oscillation near the lower cooled disk proceeds to that near the upper heated disk.
