Numerical and Experimental Investigation of Melting in the Presence of a Magnetic Field: Simulation of Low-Gravity Environment

In this paper, numerical and experimental studies are presented on melting behavior of a pure metal in the presence of a static magnetic field. When a transverse magnetic field is present and the working fluid is electrically conductive, the fluid motion in the magnetic field results in a force field (Lorentz forces) that will dampen the convective flows. Buoyancy driven flows are the focus of this study to simulate low-gravity conditions. Hartmann (Ha) number, a dimensionless parameter proportional to the strength of the magnetic field, dominates the convection flow suppression. The effects of the magnetic strength on melting rate and on the profile of the solid/melt interface are studied. The experiments are conducted with pure gallium as phase change material inside a rectangular test cell. The solid thickness at its side center position is measured by an ultrasound device and the solid/melt interface profile is captured via reflection florescent-light photography. Temperature measurements and volume expansion/contraction tracking are used to provide further details and to verify the numerical results. Magnetically induced low-gravity environments were extensively studied numerically, where the details of the flow field were obtained. The experimental and numerical results compare very well especially, at larger Hartmann numbers. The results showed that a magnetic filed could be used to simulate key melting characteristics found in actual low-gravity environments. However, under strong magnetic field, numerical simulations revealed a different three-dimensional flow structure in the melt region compared to the actual low-gravity flow fields where the flow circulations are smoothly curved.