Magnetohydrodynamic Modeling and Experimental Validation of Convection Inside Electromagnetically Levitated Co-Cu Droplets

A magnetohydrodynamic model of internal convection of a molten Co-Cu droplet processed by the ground-based electromagnetic levitation (EML) was developed. For the calculation of the electromagnetic field generated by the copper coils, the simplified Maxwell's equations were solved. The calculated Lorentz force per volume was used as a momentum source in the Navier-Stokes equations, which were solved by using a commercial computational fluid dynamics package. The RNG k-epsilon model was adopted for the prediction of turbulent flow. For the validation of the developed model, a Co16Cu84 sample was tested using the EML facility in the German Aerospace Center, Cologne, Germany. The sample was subjected to a full melt cycle, during which the surface of the sample was captured by a high-speed camera. With a sufficient undercooling, the liquid phase separation occurred and the Co-rich liquid phase particles could be observed as they were floating on the surface along streamlines. The convection velocity was estimated by the combination of the displacement of the Co-rich particles and the temporal resolution of the high-speed camera. Both the numerical and experimental results showed an excellent agreement in the convection velocity on the surface. (C) The Minerals, Metals & Materials Society and ASM International 2013