Shock wave propagation through glow discharge plasmas - Evidence of thermal mechanism of shock dispersion

Ionikh, Yu. Z.; Chernysheva, Naira V.; Yalin, Azer P.; Macheret, Sergey; Martinelli, Luigi; Miles, Richard B.

doi:10.2514/6.2000-714

Cited by 13 publications

(10 citation statements)

References 1 publication

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“…Although at that time we were not aware of [14], we gave the same name, 'partial constriction', to the effect. In [16], the effect was reproduced well in discharge tubes of different configurations and for different directions of gas flow with respect to the current, and did not vanish when the flow was terminated for a short time or water cooling of the tube wall was applied. For given conditions, the constricted part of the positive column could be adjacent to either the cathode or the anode and there was no way to predict which case would be realized.…”

Section: Introductionmentioning

confidence: 87%

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Partial constriction in a glow discharge in argon with nitrogen admixture

Ionikh

Dyatko

Meshchanov

et al. 2012

Plasma Sources Sci. Technol.

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The constriction of the positive column of a glow discharge in argon with nitrogen admixture (0.02-1%) was studied. The discharge was maintained in a tube of 2.8 cm inner diameter and 75 cm length at intermediate pressures (several tens of Torrs), at which the discharge constriction goes by a jump and the hysteresis effect is well pronounced. It was observed that the constriction begins near one of the electrodes and then the constricted region boundary propagates toward the other electrode. The reverse transition occurs in a similar way. The transition time in Ar : N 2 mixtures appears to be essentially longer (up to 1 s) than that in pure argon. By varying the power supply voltage in the course of the transition, the boundary between the diffuse and constricted forms of the discharge could be stopped at some position between the electrodes. Such a partially constricted discharge (PCD) is stable and can exist for a long time. A PCD at various locations of the boundary can be formed, different locations being realized at different discharge voltages but at the same discharge current. This corresponds to a vertical segment in the voltage-current characteristic curve. It was found that this segment lies inside the hysteresis loop and connects two branches of the conventional I -V characteristic measured without affecting the discharge during the diffuse-to-constricted or reverse transitions. Plasma parameters in the diffuse and constricted positive columns are estimated and ionization mechanisms are analyzed. The possible reasons for the low velocity of the constriction front in Ar : N 2 mixtures and the mechanisms of the stabilization of the PCD are also discussed.

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Section: Introductionmentioning

confidence: 87%

“…About 30 years later, we found accidentally that constricted and diffuse modes of a discharge in argon with a small admixture (∼0.1%) of nitrogen could co-exist at a pressure of about 50 Torr and current close to I C [16]. Although at that time we were not aware of [14], we gave the same name, 'partial constriction', to the effect.…”

Section: Introductionmentioning

confidence: 95%

Partial constriction in a glow discharge in argon with nitrogen admixture

Ionikh

Dyatko

Meshchanov

et al. 2012

Plasma Sources Sci. Technol.

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“…At the present time, no consistenttheoretical model has been able to interpret the results of these studies on the basis of nonequilibrium plasma effects alone. 6 On the other hand, recent experiments in a steady-stateglow discharge using spatiallyresolvedgas temperature measurements by ltered Rayleigh scattering 7 and in pulsed glow discharge, 7 as well as modeling calculations, 8 suggest that most of these results can be explained by the nonuniform heating of the gas ow in the discharge. A major complexity with the previous experiments on the anomalous shock weakening and dispersion in nonequilibrium plasmas is that short-duration test facilities (shock tubes and ballistic ranges) have been used.…”

Section: Introductionmentioning

confidence: 99%

Shock Wave Control by Nonequilibrium Plasmas in Cold Supersonic Gas Flows

et al. 2001

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Experimental studies of shock modi cation in weakly ionized supersonic gas ows are discussed. In these experiments, a supersonic nonequilibrium plasma wind tunnel, which produces a highly nonequilibrium plasma ow with the low gas kinetic temperature at M = 2, is used. Supersonic ow is maintained at complete steady state. The ow is ionized by a high-pressure aerodynamically stabilized dc discharge in the tunnel plenum and by a transverse rf discharge in the supersonic test section. The dc discharge is primarily used for the supersonic ow visualization, whereas the rf discharge provides high electron density in the supersonic test section. High-pressure ow visualization produced by the plasma makes all features of the supersonic ow, including shocks, boundary layers, expansion waves, and wakes, clearly visible. Attached oblique shock structure on the nose of a 35-deg wedge with and without rf ionization in a M = 2 ow is studied in various nitrogen-helium mixtures. It is found that the use of the rf discharge increases the shock angle by 14 deg, from 99 to 113 deg, which corresponds to a Mach number reduction from M = 2:0 to 1:8. Time-dependent measurements of the oblique shock angle show that the time for the shock weakening by the rf plasma, as well as the shock recovery time after the plasma is turned off, is of the order of seconds. Because the ow residence time in the test section is of the order of 10 ¹s, this result suggests a purely thermal mechanism of shock weakening due to heating of the boundary layers and the nozzle walls by the rf discharge. Gas ow temperature measurements in the test section using infrared emission spectroscopy, with carbon monoxide as a thermometric element, are consistent with the observed shock angle change. This shows that shock weakening by the plasma is a purely thermal effect. The results demonstrate the feasibility of both sustaining uniform ionization in cold supersonic nitrogen and air ows and the use of nonequilibrium plasmas for supersonic ow control. This opens a possibility for the use of transverse stable rf discharges for magnetohydrodynamic energy extraction and/or acceleration of supersonic air ows.

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“…The error bars in the temperature measurements indicate the standard deviation of the data. The measurement of this temperature profile proved critical to developing an understanding of shock propagation through weakly ionized plasmas and the effect that temperature gradients have on the shock structure [19]. This same approach may be used for the measurement of Thomson scattering [20].…”

Section: Two Variables Fixedmentioning

confidence: 99%

Flow field imaging through sharp-edged atomic and molecular `notch' filters

Miles

Yalin

Tang

et al. 2001

Meas. Sci. Technol.

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Sharp cut-off atomic and molecular notch filters simultaneously provide high spectral resolution and allow imaging by collecting light over a wide field of view. Many important properties of flow fields can be observed by imaging light elastically scattered from small particles, molecules or electrons. In order to extract information about the flow field from elastic scattering, the spectrum of the scattering must be resolved and the background scattering must be suppressed. Very high resolution, on the order of a few tens of megahertz, is usually required. The spectrum of the scattered light is broadened and shifted by the motion of the scatterers. For particles, which have relatively little thermal or acoustic motion, the spectral shift is only a function of the velocity. For molecules, the scattering spectrum is a function of the temperature, velocity and pressure of the gas as well as its composition. For electrons, the spectrum is a function of the electron temperature and electron number density in a plasma. In this paper, sharp edged notch filters made of rubidium, iodine or mercury vapour are used to image shock wave and boundary layer structure by Rayleigh scattering from particles, to image gas pressure, velocity and temperature by molecular Rayleigh scattering, and to measure electron temperature and electron number density by Thomson scattering. For molecular scattering, filter transmission is generally a function of velocity, temperature and pressure, but, under some circumstances, it is a function of only one or two variables, so a notch filter can provide single-pulse images of a specific flow field parameter.

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Shock wave propagation through glow discharge plasmas - Evidence of thermal mechanism of shock dispersion

Cited by 13 publications

References 1 publication

Partial constriction in a glow discharge in argon with nitrogen admixture

Partial constriction in a glow discharge in argon with nitrogen admixture

Shock Wave Control by Nonequilibrium Plasmas in Cold Supersonic Gas Flows

Flow field imaging through sharp-edged atomic and molecular `notch' filters

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