Natural convection in a liquid metal heated from above and influenced by a magnetic field |
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| Affiliation: | 1. Siltronic AG, Hanns-Seidel-Platz 4, 81737 München, Germany;2. Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany;3. Faculty of Physics, Mathematics and Optometry, University of Latvia, Jelgavas street 3, LV-1004 Rīga, Latvia;1. DISMA, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy;2. Institute of Atmospheric Sciences and Climate, CNR, Corso Fiume, 4, 10133 Torino, Italy;3. Institute of Geosciences and Earth Resources, CNR, Via Moruzzi 1, 56124 Pisa, Italy;1. Institute for Problems in Mechanics, Russian Academy of Sciences, 101 Vernadsky Avenue, bldg 1, 119526 Moscow, Russia;2. Bauman Moscow State Technical University, 5 Second Baumanskaya Street, 105005 Moscow, Russia;3. National Research Nuclear University MEPhI, 31 Kashirskoe Shosse, 115409 Moscow, Russia;4. Cardiff University, Heath Park, Cardiff CF14 4XY, UK;1. Universidade Federal de Santa Catarina, Departamento de Engenharia Química e de Alimentos, 88040-970 Florianópolis, Brazil;2. Universidade Federal de Santa Catarina, Campus Blumenau, 89065-300 Blumenau, Brazil;3. Università del Sannio, Facoltà di Ingegneria, 82100 Benevento, Italy;1. University of California, Los Angeles, CA, USA;2. Consultancy, Linkenheim, Germany |
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| Abstract: | Natural convection in a liquid metal heated locally at its upper surface and affected by a vertical magnetic field is investigated both experimentally and numerically. The experiments are conducted in a cylindrical test cell of large aspect ratio which is typical for application. The cell is filled with the liquid alloy GaInSn in eutectic composition. Temperature and velocity are measured using thermocouples and an electric potential probe, respectively. In the absence of the magnetic field the experimental results indicate a dependence of the Nusselt number on the Rayleigh number according to the law Nu∝Ra0.191. The particular value of the scaling exponent is in excellent agreement with the prediction of a scaling analysis for laminar, boundary layer-type flow in a low-Prandtl number fluid. Furthermore the experiments demonstrate that the Nusselt number and therefore the convective heat losses can be decreased by about 20% when a magnetic field of moderate strength (B=0.1 T) is present. The numerical simulations solve the Boussinesq equations in an axisymmetric geometry using a finite element method. The results of the simulations are both quantitatively and qualitatively in good agreement with the experimental observations. Deviations are attributed to the three-dimensional characteristics of the flow. |
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