Numerical Prediction of the Accessible Convection Range for an Electromagnetically Levitated Fe50Co50 Droplet in Space

Abstract

a series of space experiments will be performed to investigate the influence of the convection on the multiphase solidification phenomena of metallic alloys. For the success of the mission, it is of critical importance to predict the convection in molten samples under given test parameters. In this research, the convection induced in the molten Fe 50 Co 50 alloy was predicted numerically. The magnetohydrodynamic model for the ground-based electromagnetic levitator developed in the previous research was extended to the space application. The same modeling strategies were applied to the electromagnetic levitator in space. Using the numerical model, the convection under various test conditions was predicted: The flow pattern was characterized as a function of the heating current. The maximum convection velocity at various temperatures was estimated with the increasing heating current. Finally, the range of accessible convection velocity was predicted as a function of the critical undercooling of the sample, the minimum positioner control voltage, and the undercooling of the sample. The results are expected to provide critical information for the design of the space experiments and the interpretation of the results.

Experiments Using a Ground-Based Electrostatic Levitator and Numerical Modeling of Melt Convection for the Iron-Cobalt System in Support of Space Experiments

“…The validated model was applied to characterize the flow in the Fe50Co50 sample [6]. Flow pattern, maximum convection velocity, and Reynolds number (convection status: laminar or turbulent) were predicted to help design the space experiments.…”

“…For flight samples whose internal convection is of interest, numerical models were developed [5] and used [6]. The developed numerical models have been used to predict the convection status under an anticipated combination of process parameters.…”

“…Each batch has 18 samples, and the amount of mass evaporation of each sample is different depending on the composition and thermal history. After discussion among scientists, the thermal cycles of each samples are adjusted such that the total amount of mass evaporation does not exceed a designated value.For flight samples whose internal convection is of interest, numerical models were developed [5] and used [6]. The developed numerical models have been used to predict the convection status under an anticipated combination of process parameters.…”

“…By analyzing the video, the convection velocity was measured as ~0.3 m/s. Under the same parameters, the developed model showed an excellent agreement with the experiment.The validated model was applied to characterize the flow in the Fe50Co50 sample [6]. Flow pattern, maximum convection velocity, and Reynolds number (convection status: laminar or turbulent) were predicted to help design the space experiments.…”

Use of Thermophysical Properties to Select and Control Convection During Rapid Solidification of Steel Alloys Using Electromagnetic Levitation on the Space Station

“…By going to reduced gravity in space, the forces required to position the sample are much smaller, and by using EML, a broad range of convective conditions is accessible. 22 Predicting fluid flow is accomplished using magnetohydrodynamic (MHD) modeling, which has been validated by comparing liquid recirculation predictions to observations on a levitated CuCo alloy droplet. 23 Space testing of double recalescence phenomena thus has four key steps.…”