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Experimental observation of swirl accumulation in a magnetically driven flow

Published online by Cambridge University Press:  10 December 2008

I. GRANTS ,
C. ZHANG ,
S. ECKERT  and
G. GERBETH
I. GRANTS
Affiliation:
Forschungszentrum Dresden–Rossendorf, PO Box 510119, 01314 Dresden, Germanyi.grants@fzd.de
C. ZHANG
Affiliation:
Forschungszentrum Dresden–Rossendorf, PO Box 510119, 01314 Dresden, Germanyi.grants@fzd.de
S. ECKERT
Affiliation:
Forschungszentrum Dresden–Rossendorf, PO Box 510119, 01314 Dresden, Germanyi.grants@fzd.de
G. GERBETH
Affiliation:
Forschungszentrum Dresden–Rossendorf, PO Box 510119, 01314 Dresden, Germanyi.grants@fzd.de
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Abstract

Independent poloidal and azimuthal body forces are induced in a liquid metal cylinder by travelling and rotating magnetic fields of different frequencies, respectively. The bulk axial and azimuthal velocities are measured by the ultrasound Doppler method. Particle image velocimetry is used to observe the upper free surface velocity distribution. The transition from the poloidal to the azimuthal body force governed regime occurs at a fixed ratio of the respective force magnitude of around 100. This transition is marked by the formation of a concentrated vortex revealing several similarities to intense atmospheric vortices. The vortex structure is controlled by a relatively weak azimuthal force while the maximum speed of the swirl is mainly governed by the poloidal one. Under a certain force ratio the average axial velocity changes its direction in the vortex core, resembling the subsidence in an eye of a tropical cyclone or a large tornado. Multiple moving vortices encircle the vortex core in this regime.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 616 , 10 December 2008 , pp. 135 - 152
Copyright
Copyright © Cambridge University Press 2008

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