Model experiments on thermo-electromagnetic convection


Model experiments on thermo-electromagnetic convection

Cramer, A.; Zhang, X.; Gerbeth, G.

Abstract

Thermoelectromagnetic convection in electrically conducting cubic containers was studied experimentally. Two opposing side walls were cooled and heated, respectively, to produce a uniform temperature gradient. Inhomogeneous magnetic field distributions were achieved either with a small permanent magnet located above the melt layer, or with specifically shaped pole shoes of the magnetic system. Ultrasonic Doppler velocimetry measurements demonstrated that even a moderate temperature gradient may drive a distinct convection. Two different flow regimes were investigated with the permanent magnet. When it was positioned in the vicinity of an isothermal wall, with its direction of magnetisation parallel to the temperature gradient, a single vortex spreading the whole container developed while the flow might be assessed as relatively stable. Moving the magnet to the centre led to a modified distribution of the magnetic field which, in turn, altered the flow structure. The convective pattern changed to four vortices and the velocity fluctuations were intensified. A more generic case was realised with the pole shoes providing a gradient of the magnetic field only in one direction. Since the strength of the field could be raised significantly above that provided by the small permanent magnet and the area of impact onto the melt was larger, developed turbulent regimes were accomplished. Numerical results obtained for the Lorentz force and the rotor thereof support the experimental findings.

Keywords: Thermoelectricity; Model experiments; Magnetohydrodynamics; Liquid Metals; Thermocurrent; Electromagnetic stirring

  • Vortrag (Konferenzbeitrag)
    6th International Conference on Electromagnetic Processing of Materials EPM 2009, 19.-23.10.2009, Dresden, Deutschland
  • Beitrag zu Proceedings
    6th International Conference on Electromagnetic Processing of Materials EPM 2009, 19.-23.10.2009, Dresden, Deutschland
    Proceedings of the EPM 2009, 978-3-936104-65-3, 94-97

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