Dynamics of liquid metal droplets and jets influenced by a strong axial magnetic field

Spin-up from rest of a liquid metal having deformable free surface in the presence of a uniform axial magnetic field is numerically studied. Both liquid and gas phases in a vertically mounted cylinder are assumed to be an incompressible, immiscible, Newtonian fluid. Since the viscous dissipation and the Joule heating are neglected, thermal convection due to buoyancy and thermocapillary effects is not taken into account. The effects of Ekman number and Hartmann number were computed with fixing the Froude number of 1.5, the density ratio of 800, and the viscosity ratio of 50. The evolutions of the free surface, three-component velocity field, and electric current density are portrayed using the level-set method and HSMAC method. When a uniform axial magnetic field is imposed, the azimuthal momentum is transferred from the rotating bottom wall to the core region directly through the Hartmann layer. This is the most striking difference from spin-up of the nonmagnetic case.

Download Full-text

Thermocapillary convection in a cylindrical liquid-metal floating zone with a strong axial magnetic field and with a non-axisymmetric heat flux

Journal of Fluid Mechanics ◽

10.1017/s0022112097006150 ◽

1997 ◽

Vol 345 ◽

pp. 31-43 ◽

Cited By ~ 5

Author(s):

T. E. MORTHLAND ◽

J. S. WALKER

Keyword(s):

Magnetic Field ◽

Heat Flux ◽

Free Surface ◽

Liquid Metal ◽

Thermocapillary Convection ◽

Axial Magnetic Field ◽

Hot Spot ◽

Cold Spot ◽

Floating Zone ◽

Viscous Effects

This paper treats the steady three-dimensional thermocapillary convection in a cylindrical liquid-metal zone between the isothermal ends of two coaxial solid cylinders and surrounded by an atmosphere. There is a uniform steady magnetic field which is parallel to the common centrelines of the liquid zone and solid cylinders, and there is a non-axisymmetric heat flux into the liquid's free surface. The magnetic field is sufficiently strong that inertial effects and convective heat transfer are negligible, and that viscous effects are confined to thin boundary layers adjacent to the free surface and to the liquid–solid interfaces. With an axisymmetric heat flux, the axisymmetric thermocapillary convection is confined to the thin layer adjacent to the free surface, but with a non-axisymmetric heat flux, there is an azimuthal flow inside the free-surface layer from the hot spot to the cold spot with the circulation completed by flow across the inviscid central core region. This problem is related to the magnetic damping of thermocapillary convection for the floating-zone growth of semiconductor crystals in Space.

Download Full-text

Rotation of Liquid Metal Droplets Solely Driven by the Action of Magnetic Fields

Applied Sciences ◽

10.3390/app9071421 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1421 ◽

Cited By ~ 1

Author(s):

Jian Shu ◽

Shi-Yang Tang ◽

Sizepeng Zhao ◽

Zhihua Feng ◽

Haoyao Chen ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Liquid Metal ◽

Permanent Magnets ◽

The Self ◽

Rotating Magnetic Field ◽

Fluid Mixture ◽

Cooling Fluid ◽

Novel Method ◽

Metal Droplets

The self-rotation of liquid metal droplets (LMDs) has garnered potential for numerous applications, such as chip cooling, fluid mixture, and robotics. However, the controllable self-rotation of LMDs utilizing magnetic fields is still underexplored. Here, we report a novel method to induce self-rotation of LMDs solely utilizing a rotating magnetic field. This is achieved by rotating a pair of permanent magnets around a LMD located at the magnetic field center. The LMD experiences Lorenz force generated by the relative motion between the droplet and the permanent magnets and can be rotated. Remarkably, unlike the actuation induced by electrochemistry, the rotational motion of the droplet induced by magnetic fields avoids the generation of gas bubbles and behaves smoothly and steadily. We investigate the main parameters that affect the self-rotational behaviors of LMDs and validate the theory of this approach. We further demonstrate the ability of accelerating cooling and a mixer enabled by the self-rotation of a LMD. We believe that the presented technique can be conveniently adapted by other systems after necessary modifications and enables new progress in microfluidics, microelectromechanical (MEMS) applications, and micro robotics.

Download Full-text