dorsal/arxiv
View SchemaOn the effects of turbulence on a screw dynamo
| Authors | K. -H. Raedler, R. Stepanov |
|---|---|
| Categories | |
| ArXiv ID | physics/0603085 |
| URL | https://arxiv.org/abs/physics/0603085 |
| DOI | 10.1080/03091920600712049 |
Abstract
In an experiment in the Institute of Continuous Media Mechanics in Perm (Russia) an non--stationary screw dynamo is intended to be realized with a helical flow of liquid sodium in a torus. The flow is necessarily turbulent, that is, may be considered as a mean flow and a superimposed turbulence. In this paper the induction processes of the turbulence are investigated within the framework of mean--field electrodynamics. They imply of course a part which leads to an enhanced dissipation of the mean magnetic field. As a consequence of the helical mean flow there are also helical structures in the turbulence. They lead to some kind of $\alpha$--effect, which might basically support the screw dynamo. The peculiarity of this $\alpha$--effect explains measurements made at a smaller version of the device envisaged for the dynamo experiment. The helical structures of the turbulence lead also to other effects, which in combination with a rotational shear are potentially capable of dynamo action. A part of them can basically support the screw dynamo. Under the conditions of the experiment all induction effects of the turbulence prove to be rather weak in comparison to that of the main flow. Numerical solutions of the mean--field induction equation show that all the induction effects of the turbulence together let the screw dynamo threshold slightly, at most by one per cent, rise. The numerical results give also some insights into the action of the individual induction effects of the turbulence.
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"abstract": "In an experiment in the Institute of Continuous Media Mechanics in Perm\n(Russia) an non--stationary screw dynamo is intended to be realized with a\nhelical flow of liquid sodium in a torus. The flow is necessarily turbulent,\nthat is, may be considered as a mean flow and a superimposed turbulence. In\nthis paper the induction processes of the turbulence are investigated within\nthe framework of mean--field electrodynamics. They imply of course a part which\nleads to an enhanced dissipation of the mean magnetic field. As a consequence\nof the helical mean flow there are also helical structures in the turbulence.\nThey lead to some kind of $\\alpha$--effect, which might basically support the\nscrew dynamo. The peculiarity of this $\\alpha$--effect explains measurements\nmade at a smaller version of the device envisaged for the dynamo experiment.\nThe helical structures of the turbulence lead also to other effects, which in\ncombination with a rotational shear are potentially capable of dynamo action. A\npart of them can basically support the screw dynamo. Under the conditions of\nthe experiment all induction effects of the turbulence prove to be rather weak\nin comparison to that of the main flow. Numerical solutions of the mean--field\ninduction equation show that all the induction effects of the turbulence\ntogether let the screw dynamo threshold slightly, at most by one per cent,\nrise. The numerical results give also some insights into the action of the\nindividual induction effects of the turbulence.",
"arxiv_id": "physics/0603085",
"authors": [
"K. -H. Raedler",
"R. Stepanov"
],
"categories": [
"physics.flu-dyn",
"physics.plasm-ph"
],
"doi": "10.1080/03091920600712049",
"title": "On the effects of turbulence on a screw dynamo",
"url": "https://arxiv.org/abs/physics/0603085"
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