Self-excitation in a helical liquid metal flow: the Riga dynamo experiments

Gailitis, A.; Gerbeth, Günter; Gundrum, Thomas; Lielausis, O.; Lipsbergs, G.; Platacis, E.; Stefani, Frank

doi:10.1017/s0022377818000363

Cited by 15 publications

(8 citation statements)

References 37 publications

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“…The existence of a critical R m > 10 for triggering dynamo action in turbulent liquid metal flows is also supported by recent large scale laboratory experiments using specific flow patterns (see Refs. [24,25] for reviews). Furthermore, it is believed that a non-vanishing flow helicity H(t) = V (u • ω) dV is required in addition for a dynamo to act [22].…”

Section: B High Reynolds Number Turbulent Flowsmentioning

confidence: 99%

Electron spin-vorticity coupling in low and high Reynolds number pipe flows

Kazerooni,

Thieme,

Schumacher

et al. 2020

Preprint

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Spin hydrodynamic coupling is a recently discovered method to directly generate electricity from an electrically conducting fluid flow in the absence of Lorentz forces. This method relies on a collective coupling of electron spins -the internal quantum mechanical angular momentum of the electrons -with the local vorticity of a fluid flow. In this work, we experimentally investigate the spin hydrodynamic coupling in circular and non-circular capillary pipe flows and extend a previously obtained range of Reynolds numbers to smaller and larger values, 20 < Re < 21, 500, using the conducting liquid metal alloy GaInSn as the working liquid. In particular, we provide experimental evidences for the linear dependence of the generated electrical voltage with respect to the bulk flow velocity in the laminar regime of the circular pipe flow as predicted by Matsuo et al. [Phys. Rev. B. 96, 020401 (2017)]. Moreover, we show analytically that this behavior is universal in laminar regime regardless of the cross-sectional shape of the pipe. Finally, the proposed scaling law by Takahashi et al. [Nat. Phys. 12, 52 (2016)] for the generated voltage in turbulent circular pipe flows is experimentally evaluated at Reynolds numbers higher than in previous studies. Our results verify the reliability of the proposed scaling law for Reynolds numbers up to Re = 21, 500 for which the flow is in a fully developed turbulent state.

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Section: B High Reynolds Number Turbulent Flowsmentioning

confidence: 99%

Electron spin-vorticity coupling in low and high Reynolds number pipe flows

Kazerooni,

Thieme,

Schumacher

et al. 2020

Preprint

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“…Large scale dynamo experiments using liquid metals have proven that large scale field growth is possible when the system is subjected to helical forcing e.g. [152,153]. These impressive proofof principle experiments are however, at rather low magnetic Reynolds rather than the turbulent regime of astrophysical rotators.…”

Section: Dynamo and Mrimentioning

confidence: 99%

“…The experiments also do not address how large scale dynamos saturate in turbulent flows, but they can address saturation by differential rotation saturation e.g. [152,153,154]. Many numerical simulations also focus on highly idealized version of dynamos and so the experiments are not alone in simplifying the astrophysical circumstances.…”

Section: Dynamo and Mrimentioning

confidence: 99%

Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?

Blackman,

Lebedev

2020

Preprint

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The physics of astrophysical jets can be divided into three regimes: (i) engine and launch (ii) propagation and collimation, (iii) dissipation and particle acceleration. Since astrophysical jets comprise a huge range of scales and phenomena, practicality dictates that most studies of jets intentionally or inadvertently focus on one of these regimes, and even therein, one body of work may be simply boundary condition for another. We first discuss long standing persistent mysteries that pertain the physics of each of these regimes, independent of the method used to study them. This discussion makes contact with frontiers of plasma astrophysics more generally. While observations theory, and simulations, and have long been the main tools of the trade, what about laboratory experiments? Jet related experiments have offered controlled studies of specific principles, physical processes, and benchmarks for numerical and theoretical calculations. We discuss what has been done to date on these fronts. Although experiments have indeed helped us to understand certain processes, proof of principle concepts, and benchmarked codes, they have yet to solved an astrophysical jet mystery on their own. A challenge is that experimental tools used for jet-related experiments so far, are typically not machines originally designed for that purpose, or designed with specific astrophysical mysteries in mind. This presents an opportunity for a different way of thinking about the development of future platforms: start with the astrophysical mystery and build an experiment to address it.

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“…In July 2000, the saturated regime of this dynamo was also reached (Gailitis et al 2001). Since that time, 10 experimental campaigns haven been carried out (Gailitis et al 2018), the last ones in June 2016 (Gailitis and Lipsbergs 2017) and April 2017, with an ever increasing refinement of measurement techniques. Figure 1 shows, together with a sketch of the facility and a simulation of the magnetic eigenfield, a compilation of the main results in form of the experimentally and numerically determined growth rates and eigenfrequencies, both in the kinematic and in the saturated regime.…”

Section: Dynamo (Related) Experimentsmentioning

confidence: 99%

Magnetic field dynamos and magnetically triggered flow instabilities

Stefani

Albrecht

Arlt

et al. 2017

IOP Conf. Ser.: Mater. Sci. Eng.

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Magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both hydromagnetic dynamo action as well as magnetically triggered flow instabilities had been the subject of purely theoretical research. Meanwhile, however, the dynamo effect has been observed in large-scale liquid sodium experiments in Riga, Karlsruhe and Cadarache. In this paper, we summarize the results of liquid metal experiments devoted to the dynamo effect and various magnetic instabilities such as the helical and the azimuthal magnetorotational instability and the Tayler instability. We discuss in detail our plans for a precession-driven dynamo experiment and a large-scale Tayler-Couette experiment using liquid sodium, and on the prospects to observe magnetically triggered instabilities of flows with positive shear.

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Self-excitation in a helical liquid metal flow: the Riga dynamo experiments

Cited by 15 publications

References 37 publications

Electron spin-vorticity coupling in low and high Reynolds number pipe flows

Electron spin-vorticity coupling in low and high Reynolds number pipe flows

Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?

Magnetic field dynamos and magnetically triggered flow instabilities

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