Comptes Rendus
no. 7
The dynamo effect/L'effet dynamo
Interplay between experimental and numerical approaches in the fluid dynamo problem
[Couplage entre approches numériques et expérimentales dans le problème de la dynamo fluide]
Jacques Léorat1 ; Caroline Nore2, 3 
1 LUTH, Observatoire de Paris-Meudon, 92195 Meudon, France
2 LIMSI-CNRS, BP 133, 91403 Orsay cedex, France
3 Université Paris Sud 11, département de physique, 91405 Orsay cedex, France
Comptes Rendus. Physique, Volume 9 (2008) no. 7, pp. 741-748.

Après avoir connu une longue période d'études purement analytiques ou numériques, le problème de la dynamo fluide est entré dans une phase expérimentale depuis quelques années. Nous proposons un résumé des étapes numériques qui ont accompagné la réalisation de l'expérience Von Kármán Sodium (VKS) à Cadarache. Nous montrons comment des études numériques très diverses et successives ont contribué à l'optimisation progressive du montage expérimental. Enfin, le succès de l'expérience VKS2 de septembre 2006 a suscité une extension du programme numérique avec une modélisation de l'induction dans le volume des turbines. Les résultats permettent de conclure que ce n'est pas la turbulence qui contraint le nombre de Reynolds magnétique critique à la valeur observée, mais le fer doux des turbines. Des perspectives de développement numérique sont proposées en conclusion.

After years of purely analytical and numerical investigations, the dynamo fluid problem has advanced to a phase of experimental study. We present an outline of the numerical steps that have accompanied the Von Kármán Sodium (VKS) experiment at Cadarache for the past ten years. We show how various numerical studies contributed progressively to the optimization of the experimental facility. The recent success of the VKS2 experiment of September 2006 in achieving dynamo action has prompted an extension of the numerical code. Modeling of the electromotive force induced in the volume of the impellers shows that an axial dipole is excited, as observed in the experiment. We infer from these results that the observed value of the critical magnetic Reynolds number may be linked to the soft iron of the impellers and not to turbulence which occurs for any choice of materials. We conclude with proposals for further lines of numerical development.

Publié le :
DOI : 10.1016/j.crhy.2008.07.006
Keywords: Fluid dynamo, Kinematic code, Magnetic boundary conditions
Mot clés : Dynamo fluide, Simulations cinématiques, Conditions aux limites magnétiques
Jacques Léorat 1 ; Caroline Nore 2, 3

1 LUTH, Observatoire de Paris-Meudon, 92195 Meudon, France
2 LIMSI-CNRS, BP 133, 91403 Orsay cedex, France
3 Université Paris Sud 11, département de physique, 91405 Orsay cedex, France 
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Jacques Léorat; Caroline Nore. Interplay between experimental and numerical approaches in the fluid dynamo problem. Comptes Rendus. Physique, Volume 9 (2008) no. 7, pp. 741-748. doi : 10.1016/j.crhy.2008.07.006. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2008.07.006/

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