Some Studies of Free-Surface Mercury Magnetohydrodynamics

Alpher, Ralph A.; Hurwitz, H.; Johnson, R.H.; White, Donald R.

doi:10.1103/revmodphys.32.758

Cited by 32 publications

(19 citation statements)

References 13 publications

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“…Several works of particular relevance for the present investigation have shown that the existence of electromagnetic non-uniformities in the flow, which can be considered as electromagnetic obstacles, may promote the generation of internal shear layers and the appearance of flow instabilities when inertial effects are not negligible. Alpher et al (1960) studied experimentally the shallow flow of mercury in an insulating open channel in which a copper disk much thinner than the fluid depth was mounted on the bottom. They observed a stagnation zone above the disk so that the flow acted as if a solid cylinder were immersed in the flow.…”

Section: Introductionmentioning

confidence: 99%

On the flow past a magnetic obstacle

2006

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This paper analyses numerically the quasi-two-dimensional flow of an incompressible electrically conducting viscous fluid past a localized zone of applied magnetic field, denominated a magnetic obstacle. The applied field is produced by the superposition of two parallel magnetized square surfaces, uniformly polarized in the normal direction, embedded in the insulating walls that contain the flow. The area of these surfaces is only a small fraction of the total flow domain. By considering inertial effects in the analysis under the low magnetic Reynolds number approximation, it is shown that the flow past a magnetic obstacle may develop vortical structures and eventually instabilities similar to those observed in flows interacting with bluff bodies. In the small zone where the oncoming uniform flow encounters the non-negligible magnetic field, the induced electric currents interact with the field, producing a non-uniform Lorentz force that brakes the fluid and creates vorticity. The effect of boundary layers is introduced through a friction term. Due to the localization of the applied magnetic field, this term models either the Hartmann braking within the zone of high magnetic field strength or a Rayleigh friction in zones where the magnetic field is negligible. Finite difference numerical computations have been conducted for Reynolds numbers Re = 100 and 200, and Hartmann numbers in the range 1 6 Ha 6 100 (Re and Ha are based on the side length of the magnetized square surfaces). Under these conditions, a wake is formed behind the obstacle. It may display two elongated streamwise vortices that remain steady as long as the Hartmann number does not exceed a critical value. Once this value is reached, the wake becomes unstable and a vortex shedding process similar to the one observed in the flow past bluff bodies is established. Similarities and differences with the flow around solid obstacles are discussed.

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Section: Introductionmentioning

confidence: 99%

On the flow past a magnetic obstacle

2006

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“…Until now, free-surface liquid-metal research has mostly focused on how different phenomena such as surface waves, heat-transfer, and flow-stability are affected by magnetic fields alone [27][28][29][30]. The few papers that have studied the impact of a Lorentz force on free-surface liquid-metals have either not studied flowing systems [31,32] or have not studied configurations applicable to EMR within tokamaks [33]. For that reason, this paper will present data regarding the electromagnetic control of free-surface, liquid-metal flows relevant to fusion reactors and provide a simple, theoretical framework to explain the findings.…”

Section: Introductionmentioning

confidence: 99%

Demonstrating electromagnetic control of free-surface, liquid-metal flows relevant to fusion reactors

et al. 2017

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Plasma-facing components (PFC's) made from solid materials may not be able to withstand the large heat and particle fluxes that will be produced within next-generation fusion reactors. To address the shortcomings of solid PFC's, a variety of liquid-metal (LM) PFC concepts have been proposed. Many of the suggested LM-PFC designs rely on electromagnetic restraint (Lorentz force) to keep free-surface, liquid-metal flows adhered to the interior surfaces of a fusion reactor. However, there is very little, if any, experimental data demonstrating that freesurface, LM-PFC's can actually be electromagnetically controlled. Therefore, in this study, electrical currents were injected into a free-surface liquid-metal that was flowing through a uniform magnetic field. The resultant Lorentz force generated within the liquid-metal affected the velocity and depth of the flow in a controllable manner that closely matched theoretical predictions. These results show the promise of electromagnetic control for LM-PFC's and suggest that electromagnetic control could be further developed to adjust liquid-metal nozzle output, prevent splashing within a tokamak, and alter heat transfer properties for a wide-range of liquid-metal systems.

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“…The oxide film acts as a surfactant and can reduce the surface tension of a clean fluid 23,31 . Since we are interested in damping effects related to the applied magnetic field, effects due to concentration of impurities on the surface must be characterized first.…”

Section: Design Of the Channel And Liquid Metal Transfer Systemmentioning

confidence: 99%

A Liquid Metal Flume for Free Surface Magnetohydrodynamic Experiments

Nornberg¹,

Ji²,

Peterson³

et al. 2008

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We present an experiment designed to study magnetohydrodynamic effects in free-surface channel flow.The wide aspect ratio channel (the width to height ratio is about 15) is completely enclosed in an inert atmosphere to prevent oxidization of the liquid metal. A custom-designed pump reduces entrainment of oxygen, which was found to be a problem with standard centrifugal and gear pumps. Laser Doppler Velocimetry experiments characterize velocity profiles of the flow. Various flow constraints mitigate secondary circulation and end effects on the flow. Measurements of the wave propagation characteristics in the liquid metal demonstrate the surfactant effect of surface oxides and the damping of fluctuations by a cross-channel magnetic field. 47.35.Tv, 52.72.+v,

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Some Studies of Free-Surface Mercury Magnetohydrodynamics

Cited by 32 publications

References 13 publications

On the flow past a magnetic obstacle

On the flow past a magnetic obstacle

Demonstrating electromagnetic control of free-surface, liquid-metal flows relevant to fusion reactors

A Liquid Metal Flume for Free Surface Magnetohydrodynamic Experiments

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