Feasible homopolar dynamo with sliding liquid-metal contacts

Priede, Jānis; Avalos-Zuniga, Raul

doi:10.1016/j.physleta.2013.06.007

Cited by 8 publications

(36 citation statements)

References 11 publications

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“…However, provided the layers are thin enough, an anisotropic conductivity model is relevant to design such a dynamo experiment. Another dynamo experiment design with spiraling wires has been studied [16].…”

Section: Discussionmentioning

confidence: 99%

Axisymmetric dynamo action is possible with anisotropic conductivity

Plunian

Alboussière

2020

Phys. Rev. Research

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A milestone of dynamo theory is Cowling's theorem, known in its modern form as the impossibility for an axisymmetric velocity field to generate an axisymmetric magnetic field by dynamo action. Using anisotropic electrical conductivity, we show that an axisymmetric dynamo is in fact possible with a motion as simple as solid-body rotation. On top of that, the instability analysis can be conducted entirely analytically, leading to an explicit expression of the dynamo threshold, which is the only example in dynamo theory.

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Section: Discussionmentioning

confidence: 99%

Axisymmetric dynamo action is possible with anisotropic conductivity

Plunian

Alboussière

2020

Phys. Rev. Research

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“…The design consists of a flat multi-arm spiral coil placed above a fast-spinning copper disc and connected to the latter by sliding liquid-metal electrical contacts. The theoretical results obtained in [5] show a minimum magnetic Reynolds number of 40, at which the dynamo is self-excited. This can be achieved by using a copper disc of 60 cm in diameter which rotates with the frequency of 10 Hz.…”

Section: Introductionmentioning

confidence: 90%

“…, the voltage induced across the disc rotating with angular velocity Ω can be written according to the theoretical model of Priede et al [5] as…”

Section: Interpretation Of Experimental Datamentioning

confidence: 99%

“…This results in unrealistically high rotation rates which are required for dynamo to operate. To overcome this problem Priede et al [5] proposed a theoretical design of homopolar disc dynamo which uses liquid-metal sliding electrical contacts similar to those employed in homopolar motors and generators [6,7]. The design consists of a flat multi-arm spiral coil placed above a fast-spinning copper disc and connected to the latter by sliding liquid-metal electrical contacts.…”

Section: Introductionmentioning

confidence: 99%

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A homopolar disc dynamo experiment with liquid metal contacts

Avalos-Zuniga¹,

Priede²,

E.³

2017

MHD

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We present experimental results of a homopolar disc dynamo constructed at CICATA-Querétaro in Mexico. The device consists of a flat, multi-arm spiral coil which is placed above a fast-spinning metal disc and connected to the latter by sliding liquid-metal electrical contacts. Theoretically, self-excitation of the magnetic field is expected at the critical magnetic Reynolds number Rm ≈ 45, which corresponds to a critical rotation rate of about 10 Hz. We measured the magnetic field above the disc and the voltage drop on the coil for the rotation rate up to 14 Hz, at which the liquid metal started to leak from the outer sliding contact. Instead of the steady magnetic field predicted by the theory we detected a strongly fluctuating magnetic field with a strength comparable to that of Earth's magnetic field which was accompanied by similar voltage fluctuations in the coil. These fluctuations seem to be caused by the intermittent electrical contact through the liquid metal. The experimental results suggest that the dynamo with the actual electrical resistance of liquid metal contacts could be excited at the rotation rate of around 21 Hz provided that the leakage of liquid metal is prevented.

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“…Model dynamos have been extensively investigated in the past as an aid to understanding the generation of magnetic fields and their reversals in astrophysical bodies. In 1979, Moffatt pointed out that the conventional treatment of the simplest such model [Moffatt, 1979], the self-exciting Bullard dynamo [Knobloch, 1981;Hide et al, 1996;Moroz et al, 1998;Priede & Avalos-Zúñiga, 2013], was not self-consistent because it neglected the currents associated with the radial diffusion of the magnetic field, and so introduced a segmented disc dynamo in which this effect could be included in a simple way. This dynamo is described by the following system of nondimensionalized ordinary differential equations:…”

Section: Description Of the Self-exciting Homopolar Disc Dynamo And Rmentioning

confidence: 99%

Detecting Hidden Chaotic Regions and Complex Dynamics in the Self-Exciting Homopolar Disc Dynamo

Wei

Moroz

Sprott

et al. 2017

Int. J. Bifurcation Chaos

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In 1979, Moffatt pointed out that the conventional treatment of the simplest self-exciting homopolar disc dynamo has inconsistencies because of the neglect of induced azimuthal eddy currents, which can be resolved by introducing a segmented disc dynamo. Here we return to the simple dynamo system proposed by Moffatt, and demonstrate previously unknown hidden chaotic attractors. Then we study multistability and coexistence of three types of attractors in the autonomous dynamo system in three dimensions: equilibrium points, limit cycles and hidden chaotic attractors. In addition, the existence of two homoclinic orbits is proved rigorously by the generalized Melnikov method. Finally, by using Poincaré compactification of polynomial vector fields in three dimensions, the dynamics near infinity of singularities is obtained.

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Feasible homopolar dynamo with sliding liquid-metal contacts

Cited by 8 publications

References 11 publications

Axisymmetric dynamo action is possible with anisotropic conductivity

Axisymmetric dynamo action is possible with anisotropic conductivity

A homopolar disc dynamo experiment with liquid metal contacts

Detecting Hidden Chaotic Regions and Complex Dynamics in the Self-Exciting Homopolar Disc Dynamo

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