轴向振动对圆柱形液体自由表面流的影响

通过光学实时观察法研究了轴向振动对恒温圆柱形容器内液体自由表面流动行为的影响。该地面实验是在一个频率为100赫兹的电磁振动台上进行的，水－甘油的混合溶液作为模型体系。结果发现，小于100mm的振动振幅能够使自由表面产生稳定的流动。这种流动主要是由沿自由表面传播的毛细波与斯托克斯边界层效应的共同作用驱动的。随着振动振幅的变化，稳态流会呈现不同的流动花样。高振幅作用下，稳态流动趋向于周期性流甚至成为湍流，这个过程可以通过临界无量纲雷诺数(Nre)c来表征，实验中得到的(Nre)c值在10-2 ～ 10-1范围内。此外，利用示踪粒子散射技术对自由表面的流动速度进行了测量，结果显示流速随粘度的增大而减小，并且随振幅的增加呈抛物线形增长。     

Thermalcapillary Convection in NaBi（WO4）2 Melt

Surface-tension drive flow in NaBi(WO4)2 melt is visualized by means of the already proved method of high temperature in situ optical observation.The transition phenomena of the melt from steady spatial to oscillatory behaviour in melt are observed.The oscillatory thermocapillary convection is accompanied by synchronous temperature oscillations with the frequency 10Hz.The onset temperature of thermocapillary convection varies with the change of meniscus curvature of the melt free surface,which probably due to the liquid pressure at the surface associated with the curvature of meniscus.The oscillatory frequency is proportional to the temperature.Finally another kind of oscillatory thermocapillary convection with the frequency about 5Hz dominating in the undercooled melt is also observed.