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Dynamo action at low magnetic Prandtl numbers: mean flow versus fully turbulent motions

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Published 31 August 2007 Published under licence by IOP Publishing Ltd
, , Focus on Magnetohydrodynamics and the Dynamo Problem Citation Y Ponty et al 2007 New J. Phys. 9 296 DOI 10.1088/1367-2630/9/8/296

1367-2630/9/8/296

Abstract

We compute numerically the threshold for dynamo action in Taylor–Green (TG) swirling flows. Kinematic dynamo calculations, for which the flow field is fixed to its time average, are compared to dynamical runs, with the Navier–Stokes and induction equations jointly solved. The dynamo instability for the kinematic calculations is found to have two branches. The dynamical dynamo threshold at low Reynolds numbers lies within the low branch, while at high Reynolds numbers it gets closer to the high branch. Based on these results, the effect of the mean flow and of the turbulent fluctuations in TG dynamos are discussed.

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10.1088/1367-2630/9/8/296