Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 25: Fluid dynamics I

DY 25.4: Vortrag

Donnerstag, 28. Februar 2008, 12:15–12:30, MA 001

The Wake of a Magnetic Obstacle — Evgeny Votyakov and •Egbert Zienicke — Institut für Physik, Technische Universität Ilmenau, 98684 Ilmenau, Germany

When a liquid metal moves relative to a localized magnetic field — a magnetic obstacle — the induced eddy currents produce a Lorentz force retarding the flow according to Lenz’s rule and, moreover, creating vorticity. Whereas the flow pattern around a mechanical obstacle, such as for example a circular cylinder, is well documented the structure of the wake of a magnetic obstacle is poorly understood even in the seemingly simple steady state.

We demonstrate [1] that the stationary flow pattern is considerably more complex than in the wake behind an ordinary body. The steady flow is shown to undergo two bifurcations (rather than one) and to involve up to six (rather than just two) vortices. We find that the first bifurcation leads to the formation of a pair of vortices within the region of magnetic field that we call inner magnetic vortices, whereas a second bifurcation gives rise to a pair of attached vortices that are linked to the inner vortices by connecting vortices.

[1] E.V. Votyakov, Yu. Kolesnikov, O. Andreev, E. Zienicke, A. Thess, Phys. Rev. Lett. 98 (2007) 144504.