Assessment of Electromagnetic Stirrer Agitated Liquid Metal Flows by Dynamic Neutron Radiography
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PITE age-old roots, there is still a demand and room for improvements in metallurgical processing. Energy efficiency and purity constraints are the current drivers. Heating, melting, and stirring of liquid metal by means of electromagnetic fields produced by alternating current are state of the art. Generally, the electromagnetically induced liquid metal flows form a class of turbulent flows, which can be characterized by multi-vortical structure with intense fluctuations between them. These fluctuations are responsible for heat and mass transfer[1,2] and, therefore, are subject of clear industrial interest. The potential for optimization here is strongly coupled to advances in numerical modeling of the mentioned processes. There has been a significant progress in numerical modeling of the flows, such as Large Eddy Simulation performed for induction crucible and channel furnaces[1,3,4]; however, these simulations lack the validation/disproof based on an effective non-invasive experimental method. Developing a benchmark system, which allows the comparison of simulations and experimental observations for relevant conditions of an induction stirrer of a furnace, is thus a pressing task that will ultimately allow for the tuning of numerical models. MIHAILS SˇCˇEPANSKIS and ANDRIS JAKOVICˇS are with the Laboratory for Mathematical Modelling of Environmental and Technological Processes, Department of Physics, University of Latvia, Zellu iela 25, Riga, 1002 Latvia. Contact e-mail: mihails.scepanskis@ ¯ RTIN¸Sˇ SARMA is with the Institute of Fluid Dynamics, lu.lv MA Helmholtz-Zentrum Dresden-Rossendorf, 01328, Dresden, Germany. PETER VONTOBEL, PAVEL TRTIK, and KNUD THOMSEN are with the Paul Scherrer Institut, 5232 Villigen, Switzerland. TOMS BEINERTS is with the Institute of Physics, University of Latvia, Salaspils, 2169 Latvia. Manuscript submitted August 25, 2016. Article published online January 11, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
The invasive experimental study of single-phase flow dates back to the 1970s,[5,6] and there has been a steady improvement in the available probes and methods since then.[1,3] The Doppler shift method as an non-invasive tool is known from late 1980s[7]; however, it has a significant limitation in spatial resolution. Recently, the new Inductive Flow Tomography method was presented.[8,9] This method has high temporal and spatial resolution; however, it is based on numerical reconstruction of the flow, and needs to know conductivity of the liquid and assumes its homogeneity. Such procedure may induce some additional error in case of two-phase flow or some impurities. Results for two-phase systems have been much more scarce.[10,11] While some limited experimental information can be obtained from X-ray radiography methods,[12–15] these hit a fundamental limit given by the opacity of the investigated metallic melts. Contrary to X-rays, neutrons interact with nuclei, and therefore the elemental cross section for neutron does not scale with the atomic number. Thanks to the low neutron attenuation of
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