Effect of electron density on shock wave propagation in optically pumped plasmas

White, Allen; Palm, Peter; Plönjes, Elke; Subramaniam, V. V.; Adamovich, Igor V.

doi:10.1063/1.1435829

Cited by 6 publications

(2 citation statements)

References 21 publications

(39 reference statements)

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“…White et al [56] have used a similar experimental arrangement but produced the plasma with a CO laser optically pumping the vibrational states to a high level, the high vibrationl states then collisionally causing associative ionization of CO in the 3.5 Torr CO component in a 70-100 Torr argon absorption cell. The novel idea used in this experiment was to add a small amount of O 2 , which allows variation of n e over more than an order of magnitude while keeping the other plasma parameters (T e = 0.5 eV), pressure and temperature, unchanged.…”

Section: Diffuse Dischargesmentioning

confidence: 99%

“…In the work reported in two recent papers [53,56] the measurement conditions, such as the gas temperatures and plasma parameters, were carefully documented and the authors used the reliable laser Schlieren method for shock broadening measurement. The similarity between the two experiments arises from the fact that under both measurement conditions the mean electron energy was kept to the minimum possible value for the given electron density; this leads to the electron Debye length being smaller than the shock thickness.…”

Section: Diffuse Dischargesmentioning

confidence: 99%

See 1 more Smart Citation

Plasmas in high speed aerodynamics

Bletzinger¹,

Ganguly²,

Wie³

et al. 2005

J. Phys. D: Appl. Phys.

292

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A review is presented of the studies in the former Soviet Union and in the USA of the mutual interactions of plasmas and high speed flows and shocks. There are reports from as early as the 1980s of large changes in the standoff distance ahead of a blunt body in ballistic tunnels, significantly reduced drag and modifications of travelling shocks in bounded weakly ionized gases. Energy addition to the flow results in an increase in the local sound speed that leads to expected modifications of the flow and changes to the pressure distribution around a vehicle due to the decrease in local Mach number. The critical question was, did a plasma provide a significant energy multiplier for the system? There have been a large number of experimental studies on the influence of a weakly ionized plasma on relatively low Mach number shocks and inherently also on the influence of the shock on the plasma. This literature is reviewed and illustrated with representative examples. The convergence through more controlled experiments and improved modelling to a physics understanding of the effects being essentially due to heating is outlined. It is demonstrated that the heating in many cases is global; however, tailored experiments with positive columns, dielectric barrier discharges and focused microwave plasmas can produce very localized heating. The latter appears more attractive for energy efficiency in flow control. Tailored localized ionization and thermal effects are also of interest for high speed inlet shock control and for producing reliable ignition for short residence time combustors, and work in these areas is also reviewed.

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Section: Diffuse Dischargesmentioning

confidence: 99%

Section: Diffuse Dischargesmentioning

confidence: 99%

Plasmas in high speed aerodynamics

Bletzinger¹,

Ganguly²,

Wie³

et al. 2005

J. Phys. D: Appl. Phys.

292

View full text Add to dashboard Cite

show abstract

Shock velocity in weakly ionized nitrogen, air, and argon

Siefert

2007

Physics of Fluids

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The goal of this research was to determine the principal mechanism(s) for the shock velocity increase in weakly ionized gases. This paper reports experimental data on the propagation of spark-generated shock waves (1<Mach<3) into weakly ionized nitrogen, air, and argon glow discharges (1<p<20Torr). In order to distinguish between effects due solely to the presence of electrons and effects due to heating of the background gas via elastic collisions with electrons, the weakly ionized discharge was pulsed on/off. Laser deflection methods determined the shock velocity, and the electron number density was collected using a microwave hairpin resonator. In the afterglow of nitrogen, air, and argon discharges, the shock velocity first decreased, not at the characteristic time for electrons to diffuse to the walls, but rather at the characteristic time for the centerline gas temperature to equilibrate with the wall temperature. These data support the conclusion that the principal mechanism for the increase in shock velocity in weakly ionized gases is thermal heating of the neutral gas species via elastic collisions with electrons.

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Revisiting the thermal effect on shock wave propagation in weakly ionized plasmas

Zhou

Yang

2016

Physics of Plasmas

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Many researchers have investigated shock propagation in weakly ionized plasmas and observed the following anomalous effects: shock acceleration, shock recovery, shock weakening, shock spreading, and splitting. It was generally accepted that the thermal effect can explain most of the experimental results. However, little attention was paid to the shock recovery. In this paper, the shock wave propagation in weakly ionized plasmas is studied by fluid simulation. It is found that the shock acceleration, weakening, and splitting appear after it enters the plasma (thermal) region. The shock splits into two parts right after it leaves the thermal region. The distance between the splitted shocks keeps decreasing until they recover to one. This paper can explain a whole set of features of the shock wave propagation in weakly ionized plasmas. It is also found that both the shock curvature and the splitting present the same photoacoustic deflection (PAD) signals, so they cannot be distinguished by the PAD experiments.

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Effect of electron density on shock wave propagation in optically pumped plasmas

Abstract: Electron density and recombination rate measurements in CO-seeded optically pumped plasmas

Cited by 6 publications

References 21 publications

Plasmas in high speed aerodynamics

Plasmas in high speed aerodynamics

Shock velocity in weakly ionized nitrogen, air, and argon

Revisiting the thermal effect on shock wave propagation in weakly ionized plasmas

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