Magnetohydrodynamic Modeling and Experimental Validation of Convection Inside Electromagnetically Levitated Co-Cu Drople
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ELECTROMAGNETIC levitation (EML) provides a favorable environment for high temperature processing of reactive materials by innovatively eliminating containers. Since its introduction to the materials processing field decades ago,[1] EML has been successfully applied to the fields of thermophysical property measurements and the phase selection during solidification. Ground-based EML always involves a significant amount of convection in the sample, which conveys a critical effect on the validity of the results of some thermophysical properties and phase selection.[2,3] For instance, for the measurement of molecular viscosity, it must be ensured that the convection in the melt is in a laminar regime. In turbulence, momentum transfer by turbulent eddies dominates such that one should obtain much larger viscosity. Other properties measured by ground-based EML, such as thermal con-
JONGHYUN LEE, Postdoctoral Research Associate, is with the Department of Mechanical Engineering, Tufts University, 200 College Avenue, Medford, MA 02155, and also with the Department of Mechanical & Industrial Engineering, University of Massachusetts, 160 Governors Drive, Amherst, MA 01002. Contact e-mail: jonghyunlee@ ecs.umass.edu DOUGLAS M. MATSON, Associate Professor, is with the Department of Mechanical Engineering, Tufts University. SVEN BINDER and MATTHIAS KOLBE, Researchers, and DIETER HERLACH, Professor, are with the Institute of Materials Physics in Space, German Aerospace Center (DLR), Linder Ho¨he, 51147 Cologne, Germany. ROBERT W. HYERS, Professor, is with the Department of Mechanical & Industrial Engineering, University of Massachusetts. Manuscript submitted September 23, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
ductivity, are also influenced by stirring in the sample. Therefore, it is of critical importance to understand the fundamental features of the convection in EML. Experimental approaches to characterize the convection in EML are very limited since samples are opaque, reactive, and featureless.[4] Moreover, a strong and alternating magnetic field should also create a massive noise in the data acquisition systems. By these reasons, many research groups who challenged this problem have been dependent on either analytical or numerical techniques.[5–13] Analytical or numerical characterization of the convection in EML is a challenging task, in that phenomena related to the electricity, magnetism, fluid motion, and heat transfer are intertwined with one another. One vulnerable point of analytical and numerical models for the convection in EML is the fact that experimental validation is extremely difficult. Hyers et al.[14] indirectly and qualitatively validated their numerical model by observing the movement of tracer particles floating on the Pd82Si18 sample tested by TEMPUS EML. However, publications with the quantitative validation of convection velocity in EML can hardly be found. In this research a numerical model of convection inside electromagnetically levitated droplets is developed and the simulation result is validat
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