Development of molten metal holder of Faraday type

本研究是为了开发一种熔融金属支架而进行的。由直流电流和直流磁场相互作用产生的电磁力使熔融金属保持不接触。我们确定了在各种条件下自由表面的形状。同时确定了与反馈控制相关的暂态响应和频率特性。通过对汞的分析和实验，得到了以下结果：(1)利用电磁力可以实现熔融金属的无接触稳定保持。(2)当电磁力无旋转时，流体中不产生流动。在熔融金属上施加水平直流电流和成直角交叉的不均匀垂直直流磁场，形成稳定的凹或凸表面。(3)当电磁力带有旋转部分时，在流体中引起再循环流动；然而，随着磁场变强，流动变弱。通过改变电极的位置和磁场的分布，可以实现自由表面的各种形状。(4)当突然施加电磁力时，产生表面波。这些波随着磁场的增强而消失。存在一个合适的磁场强度，可以将固定表面所需的时间减少到最小。(5)交流部分的电流使表面不稳定。非定常电磁力引起液态金属的垂直或水平晃动。雷诺数或韦伯数的增加将使系统不稳定，而斯图尔特数的增加将使系统稳定。

This study was conducted for the development of a molten metal holder. The molten metal is held without contact by the electromagnetic force which is induced by the interaction between DC current and DC magnetic field. We determined the the shape of the free surface under various conditions. Transient response and frequency characteristics were also determined with relation to the feedback control. From the analysis and the experiments with mercury, following results were obtained.(1) Stable holding of the molten metal without contact can be realized by using an electromagnetic force.(2) When the electromagnetic force is irrotational, no flow is induced in the fluid. In case that the horizontal DC electric current and nonuniform vertical DC magnetic field which cross each other in right angle are applied to the molten metal, stable concave or convex surface is formed.(3) In case of the electromagnetic force with a rotational part, a recirculating flow is induced in the fluid ; however, the flow becomes weak as the magnetic field becomes strong. Various shapes of the free surface can be realized by changing both the position of the electrode and the distribution of the magnetic field.(4) When the electromagnetic force is suddenly applied, surface waves are generated. These waves disappear as the magnetic field becomes strong. There exists a suitable magnetic field strength to reduce the time required for the stationary surface to a minimum.(5) The AC part of the electric current make the surface unstable. Unsteady electromagnetic force causes the vertical or horizontal sloshing of the liquid metal. An increase of the Reynolds number or of the Weber number will make the system unstable but an increase of the Stuart number will make the system stable.