Flow velocity measurement in high-current arcs using Doppler-shifted plasma scattering

Irie, M.; Barrault, M.

doi:10.1088/0022-3727/10/12/009

Cited by 9 publications

(3 citation statements)

References 8 publications

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“…where ^=r,K^,A/o/^=//o^/V27r77p'/2 (13) is the magnetic Reynolds number (or Lundquist number, since the characteristic velocity is VAC)-Equations (10) and (12) are of the form…”

Section: Birue) Dt -^-V-'virue)mentioning

confidence: 99%

Vorticity model of flow driven by purely poloidal currents

Bellan

1992

Phys. Rev. Lett.

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The axisymmetric, incompressible, viscoresistive magnetohydrodynamic equations for purely poloidal currents I(r,z) are transformed into three coupled scalar partial differential equations. These show that finite dl/dz acts as a volumetric source of fluid "vorticity" which drives strong poloidal flows (jets). PACS numbers: 52.80.Mg, 52.55.Ez, 52.75.Di, 98.60.Qs Axisymmetric, purely poloidal current configurations are found in a wide variety of conducting fluids and plasmas. Terrestrial examples include electric furnace [l] and other industrial arcs [2], magnetoplasma-dynamic (MPD) thrusters [3], z pinches [4], Marshall guns [5], thyratrons [6], ignitrons, lightning, liquid metals [7], and electrolytes. Although astrophysical plasmas are typically assumed to have both toroidal and poloidal currents, there presumably exist situations where the current is primarily poloidal (Refs. [8,9] are possible examples). The most interesting property of these configurations, a strong axial acceleration of fluid or plasma away from regions of constricted current, was first discussed by Maecker [10]. Axially directed fluid velocities of the order of the Alfven velocity can result from this acceleration, and in a high current arc most [11] of the electrical energy input can go into translational kinetic energy, rather than into thermal energy or radiation. The thrust associated with this axial flow is the basis of the MPD rocket engine, while in electric arc furnaces, viscous dissipation of the arc kinetic energy heats the metal being processed. Arc axial flow velocities have been measured by Bowman [12] and by Irie and Barrault [13]. Reed [14] graphically demonstrated the flow in liquid mercury. Numerical magnetohydrodynamic (MHD) models for electric arc furnaces have been discussed by McKelliget and Szekely [15] and for MPD thrusters by La Pointe [16].We present here a new interpretation of this phenomenon which shows that axial current inhomogeneity acts as a volumetric source of fluid "vorticity," Our model assumes an incompressible, constant density fluid; this is reasonable for liquids but is an oversimplification for gases (compressibility considerations will alter the response to the vorticity generation mechanism discussed here, but should not aff'ect the mechanism itself). The relevant equations are the MHD equation of motion p[9U/d/-fUVU]=JxB-V/>+pvV2u,where p and v are, respectively, the mass density and kinematic viscosity; the MHD Ohm's law and Ampere's and Faraday's laws VxB=A^oJ, VxE=-9B/a/.(2)The electric field is E= -VO -9A/9r and we choose the Coulomb gauge V-A=0, i.e., A=V/xV^, where / is a scalar function and we use cylindrical coordinates (/•,0,z) sothat V^ = ^/r. Since the 0 component of Eq.(1), birUe) dt -^-V-'VirUe)=pv ri--f(rUe) or r or + -^(rUe) dz'(4) contains no driving force term, finite Ue is possible only in the exceptional situations where (i) it has been imposed as an initial condition at the initial time ^o (after whichUe transiently decays), or (ii) it is imposed as a boundary condition on some ...

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“…where ^=r,K^,A/o/^=//o^/V27r77p'/2 (13) is the magnetic Reynolds number (or Lundquist number, since the characteristic velocity is VAC)-Equations (10) and (12) are of the form…”

Section: Birue) Dt -^-V-'virue)mentioning

confidence: 99%

Vorticity model of flow driven by purely poloidal currents

Bellan

1992

Phys. Rev. Lett.

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“…5 Laboratory examples include coaxial magnetized plasma guns used to make spheromaks [6][7][8] and MHD thrusters being investigated for space propulsion. In contrast to Marshall guns 9 and electric arcs 10,11 which have a toroidal magnetic field but no poloidal field, the jets considered here have both toroidal and poloidal fields and so have magnetic helicity.…”

Section: Introductionmentioning

confidence: 99%

Experiments and models of MHD jets and their relevance to astrophysics and solar physics

Bellan

2018

Physics of Plasmas

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Magnetohydrodynamic (MHD)-driven jets involve poloidal and toroidal magnetic fields, finite pressure gradients, and unbalanced forces. The mechanism driving these jets is first discussed qualitatively by decomposing the magnetic force into a curvature and a gradient component. The mechanism is then considered quantitatively by consideration of all terms in the three components of the MHD equation of motion and in addition, the implications of Ampere's law, Faraday's law, the ideal Ohm's law, and the equation of continuity. The analysis shows that jets are self-collimating with the tip of the jet moving more slowly than the main column of the jet so there is a continuous stagnation near the tip in the jet frame. Experiments supporting these conclusions are discussed and it is shown how this mechanism relates to jets in astrophysical and solar corona contexts.

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“…Both temperature and concentration may be obtained when an absolute intensity calibration is available. In all cases the addition of copper narrows the spectrum and increases the scatter intensity, making scattering measurements easier to perform (Irie and Barrault 1977).…”

Section: Discussionmentioning

confidence: 99%

The measurement of electrode vapour concentration from light-scattering experiments in a high-current arc plasma in air

Irie

Barrault

1978

J. Phys. D: Appl. Phys.

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In the arc discharge in air with copper electrodes, the characteristics are very strongly affected by the local density of the electrode vapour, because of its lower ionisation potential compared with those of the components of air, nitrogen and oxygen. In this paper, from the assumption of local thermodynamic equilibrium, the Saha-Eggert equation is solved and the copper vapour effect on the laser light scattering profile is determined so that the copper concentration may be obtained.

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Flow velocity measurement in high-current arcs using Doppler-shifted plasma scattering

Cited by 9 publications

References 8 publications

Vorticity model of flow driven by purely poloidal currents

Vorticity model of flow driven by purely poloidal currents

Experiments and models of MHD jets and their relevance to astrophysics and solar physics

The measurement of electrode vapour concentration from light-scattering experiments in a high-current arc plasma in air

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