Residual fluid flow in liquid metallic droplets processed in the space station electromagnetic levitation facility

Abstract

The electromagnetic levitation facility on board the International Space Station is used to investigate contactlessly and without gravity-induced convection thermophysical properties and microstructure formations of hot, highly reactive metallic liquids. Despite the widely forceless microgravity environment, the small remaining electromagnetic levitation forces still drive residual convective fluid flows inside the levitated droplet, which may disturb the measurements. Thus, the knowledge of the flow velocities is critical to interpret and evaluate the measurement results. In previous investigations of Xiao and co-workers, a great amount of numerical magneto hydrodynamics calculations were performed with many different material properties and source force terms. The results for the maximum flow velocities hereof were analytically characterized by surrogate models consisting of multi-dimensional, high-order regression analysis. The present work offers another analytical description of these numerical results. Derived based on physical relations, it provides a simpler and physically more illustrative presentation.