dorsal/arxiv
View SchemaAmbivalent effects of added layers on steady kinematic dynamos in cylindrical geometry: application to the VKS experiment
| Authors | F. Stefani, M. Xu, G. Gerbeth, F. Ravelet, A. Chiffaudel, F. Daviaud, J. Léorat |
|---|---|
| Categories | |
| ArXiv ID | physics/0511149 |
| URL | https://arxiv.org/abs/physics/0511149 |
| DOI | 10.1016/j.euromechflu.2006.02.002 |
| Journal | Eur.J.Mech.B Fluids 25 (2006) 894-908 |
Abstract
The intention of the ''von Karman sodium'' (VKS) experiment is to study the hydromagnetic dynamo effect in a highly turbulent and unconstrained flow. Much effort has been devoted to the optimization of the mean flow and the lateral boundary conditions in order to minimize the critical magnetic Reynolds number and hence the necessary motor power. The main focus of this paper lies on the role of ''lid layers'', i.e. layers of liquid sodium between the impellers and the end walls of the cylinder. First, we study an analytical test flow to show that lid layers can have an ambivalent effect on the efficiency of the dynamo. The critical magnetic Reynolds number shows a flat minimum for a small lid layer thickness, but increases for thicker layers. For the actual VKS geometry it is shown that static lid layers yield a moderate increase of the critical magnetic Reynolds number by approximately 12 per cent. A more dramatic increase by 100 until 150 per cent can occur when some rotational flow is taken into account in those layers. Possible solutions of this problem are discussed for the real dynamo facility.
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"abstract": "The intention of the \u0027\u0027von Karman sodium\u0027\u0027 (VKS) experiment is to study the\nhydromagnetic dynamo effect in a highly turbulent and unconstrained flow. Much\neffort has been devoted to the optimization of the mean flow and the lateral\nboundary conditions in order to minimize the critical magnetic Reynolds number\nand hence the necessary motor power. The main focus of this paper lies on the\nrole of \u0027\u0027lid layers\u0027\u0027, i.e. layers of liquid sodium between the impellers and\nthe end walls of the cylinder. First, we study an analytical test flow to show\nthat lid layers can have an ambivalent effect on the efficiency of the dynamo.\nThe critical magnetic Reynolds number shows a flat minimum for a small lid\nlayer thickness, but increases for thicker layers. For the actual VKS geometry\nit is shown that static lid layers yield a moderate increase of the critical\nmagnetic Reynolds number by approximately 12 per cent. A more dramatic increase\nby 100 until 150 per cent can occur when some rotational flow is taken into\naccount in those layers. Possible solutions of this problem are discussed for\nthe real dynamo facility.",
"arxiv_id": "physics/0511149",
"authors": [
"F. Stefani",
"M. Xu",
"G. Gerbeth",
"F. Ravelet",
"A. Chiffaudel",
"F. Daviaud",
"J. L\u00e9orat"
],
"categories": [
"physics.flu-dyn",
"astro-ph",
"physics.plasm-ph"
],
"doi": "10.1016/j.euromechflu.2006.02.002",
"journal_ref": "Eur.J.Mech.B Fluids 25 (2006) 894-908",
"title": "Ambivalent effects of added layers on steady kinematic dynamos in cylindrical geometry: application to the VKS experiment",
"url": "https://arxiv.org/abs/physics/0511149"
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