Effect of magnetic boundary conditions on the dynamo threshold of von Kármán swirling flowsC. Gissinger1, 2, A. Iskakov3, 4, S. Fauve1 and E. Dormy2, 3
1 Laboratoire de Physique Statistique, École Normale Supérieure CNRS - 24 rue Lhomond, F-75005 Paris, France, EU
2 Laboratoire de Radioastronomie, École Normale Supérieure CNRS - 24 rue Lhomond, F-75005 Paris, France, EU
3 Institut de Physique du Globe de Paris - Paris, France, EU
4 U.C.L.A., Physics Department - Los Angeles, CA, USA
received 25 February 2008; accepted in final form 26 March 2008; published April 2008
published online 7 April 2008
We study the effect of different boundary conditions on the kinematic dynamo threshold of von Kármán type swirling flows in a cylindrical geometry. Using an analytical test flow, we model different boundary conditions: insulating walls all over the flow, effect of sodium at rest on the cylinder side boundary, effect of sodium behind the impellers, effect of impellers or side wall made of a high-magnetic-permeability material. We find that using high-magnetic-permeability boundary conditions decreases the dynamo threshold, the minimum being achieved when they are implemented all over the flow.
91.25.Cw - Origins and models of the magnetic field; dynamo theories.
47.65.-d - Magnetohydrodynamics and electrohydrodynamics.
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