The von Karman Sodium experiment: Turbulent dynamical dynamos

Romain Monchaux (1) , Michaël Berhanu (2) , Sébastien Aumaître (2) , Arnaud Chiffaudel (1) , François Daviaud (1) , Bérengère Dubrulle (1) , Florent Ravelet (1) , Stéphan Fauve (2) , Nicolas Mordant (2) , François Pétrélis (2) , Mickaël Bourgoin (3) , Philippe Odier (4) , Jean-François Pinton (4) , Nicolas Plihon (4) , Romain Volk (4)

1 SPEC - UMR3680 - Service de physique de l'état condensé
2 LPS - Laboratoire de Physique Statistique de l'ENS
3 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]
4 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

The von Karman Sodium (VKS) experiment studies dynamo action in the flow generated inside a cylinder filled with liquid sodium by the rotation of coaxial impellers (the von Karman geometry). We first report observations related to the self-generation of a stationary dynamo when the flow forcing is R-pi-symmetric, i.e., when the impellers rotate in opposite directions at equal angular velocities. The bifurcation is found to be supercritical with a neutral mode whose geometry is predominantly axisymmetric. We then report the different dynamical dynamo regimes observed when the flow forcing is not symmetric, including magnetic field reversals. We finally show that these dynamics display characteristic features of low dimensional dynamical systems despite the high degree of turbulence in the flow.

Mots clés: Bifurcation; Confined flow; Liquid metals; Sodium; Turbulence

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Romain Monchaux, Michaël Berhanu, Sébastien Aumaître, Arnaud Chiffaudel, François Daviaud, et al.. The von Karman Sodium experiment: Turbulent dynamical dynamos. Physics of Fluids, 2010, 21 (3), pp.035108. ⟨10.1063/1.3085724⟩. ⟨hal-00492266⟩