Effects of hydrogen impurities on shock structure and stability in ionizing monatomic gases: 2. Krypton

1977 ◽  
Vol 55 (14) ◽  
pp. 1269-1279 ◽  
Author(s):  
I. I. Glass ◽  
W. S. Liu ◽  
F. C. Tang
Keyword(s):  
Shock Tube ◽  
Shock Front ◽  
Initial Pressure ◽  
Adsorbed Water ◽  
Radiation Energy ◽  
Shock Structure ◽  
Wall Material ◽  
Quasi Equilibrium ◽  
Relaxation Length ◽  
Electron Cascade

At shock Mach numbers [Formula: see text] in pure krypton, at initial pressures p0 ~ 5 Torr, and final electron number densities ne ~ 1017 cm−3, the translational shock front in a 10 cm × 18 cm hypervelocity shock tube develops sinusoidal instabilities which affect the entire shock structure including the ionization relaxation region, the electron-cascade front and the final quasi-equilibrium state. By adding a small amount of hydrogen (~0.5% of the initial pressure), the entire flow is stabilized. However, the relaxation length for ionization is drastically reduced to about one half of its pure-gas value. Unlike argon the stability appears to diminish with the addition of hydrogen beyond about 0.5%. Using the familiar two-step collisional model coupled with radiation-energy loss and the appropriate chemical reactions, it was possible from dual-wavelength interferometric measurements to deduce a more precise value for the krypton–krypton collision excitation cross-section, S*Kr–Kr = 1.2 × 10−19 cm2/eV, with or without the presence of hydrogen impurities. The reason for the success of hydrogen, and not other gases, in bringing about stabilized Shock waves in argon and krypton is not clear. It was also found that the electron-cascade front approached closely to the translational-shock front with increasing proximity to the shock-tube wall. This effect appears independent of the wall material and is not affected by the evolution of adsorbed water vapour from the walls or by water added deliberately to the test gas. The sinusoidal instabilities investigated here may offer some important clues to the abatement of instabilities that lead to detonations and explosions.

Shock tube flows past partially opened diaphragms

2008 ◽  
Vol 602 ◽  
pp. 267-286 ◽  
Author(s):  
PAOLO GAETANI ◽  
ALBERTO GUARDONE ◽  
GIACOMO PERSICO
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Shock Front ◽  
Compressible Flows ◽  
Wave Speed ◽  
Initial Pressure ◽  
Normal Shock ◽  
Relative Area ◽  
Simple Analytical Model ◽  
Pressure Oscillations

Unsteady compressible flows resulting from the incomplete burst of the shock tube diaphragm are investigated both experimentally and numerically for different initial pressure ratios and opening diameters. The intensity of the shock wave is found to be lower than that corresponding to a complete opening. A heuristic relation is proposed to compute the shock strength as a function of the relative area of the open portion of the diaphragm. Strong pressure oscillations past the shock front are also observed. These multi-dimensional disturbances are generated when the initially normal shock wave diffracts from the diaphragm edges and reflects on the shock tube walls, resulting in a complex unsteady flow field behind the leading shock wave. The limiting local frequency of the pressure oscillations is found to be very close to the ratio of acoustic wave speed in the perturbed region to the shock tube diameter. The power associated with these pressure oscillations decreases with increasing distance from the diaphragm since the diffracted and reflected shocks partially coalesce into a single normal shock front. A simple analytical model is devised to explain the reduction of the local frequency of the disturbances as the distance from the leading shock increases.

scholarly journals Initial pressure of the shock front launched by a streamer discharge in water

AIP Advances ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 075214
Author(s):  
Xiaodong Xue ◽  
Xiaoqiong Wen ◽  
Yuantian Yang ◽  
Liru Wang ◽  
Xue Wang
Keyword(s):  
Shock Front ◽  
Initial Pressure ◽  
Streamer Discharge

The relaxation zone behind normal shock waves in a dusty reacting gas. Part 2. Diatomic gases

1984 ◽  
Vol 31 (1) ◽  
pp. 115-140 ◽  
Author(s):  
O. Igra ◽  
G. Ben-Dor
Keyword(s):  
Shock Wave ◽  
Heat Capacity ◽  
Shock Front ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Relaxation ◽  
Nitrogen Gas ◽  
Relaxation Length ◽  
Relaxation Zone ◽  
Post Shock

The propagation of a strong normal shock wave into a quiescent mixture of nitrogen gas seeded with small, spherical inert dust particles is studied. While crossing the shock front, the gaseous phase of the suspension experiences a sudden change in temperature, pressure, density and velocity. (These changes can easily be evaluated using the Rankine-Hugoniot relations.) The solid phase of the suspension (dust) is initially unaffected by the shock wave. As a result, immediately behind the shock front, one phase of the suspension (the nitrogen gas) is in a state of relatively high temperature and low velocity while the other (the dust) is in a state of relatively low temperature and high velocity. Owing to these differences in temperature and velocity, intense heat transfer and viscous interactions between the two phases take place leading eventually to a new state of equilibrium that is reached farther downstream of the shock front. The flow field where these interactions take place, the relaxation zone, is solved numerically. It is shown that the spatial extent of this zone is strongly affected by the mass concentration of the dust in the suspenson and its physical properties (size, density and specific-heat capacity). These parameters also affect the post-shock equilibrium suspension properties. It was found that increasing the dust concentration results in a shorter kinematic relaxation zone, higher post-shock suspension pressure, density and temperature, and lower velocity, as compared to a similar pure-gas case. Increasing the dust particle density or its diameter results in a longer relaxation zone and a higher post-shock equilibrium suspension pressure, density and temperature. Changes in the dust specific-heat capacity affect the extent at the thermal relaxation length and the suspension temperature and density; they do not affect the extent of the kinematic relaxation length or the post-shock suspension pressure and velocity. For the range of dust concentration, size, density, specific-heat capacity and shock-wave Mach number investigated, the kinematic relaxation zone is always longer than the thermal relaxation zone.

Numerical Calculations on Reflection Processes of Ionizing Shocks on the End Wall of a Shock Tube

1977 ◽  
Vol 32 (9) ◽  
pp. 986-993 ◽  
Author(s):  
Yasunari Takano ◽  
Teruaki Akamatsu
Keyword(s):  
Shock Tube ◽  
Initial Pressure ◽  
Inviscid Flow ◽  
Incident Shock ◽  
Numerical Calculations ◽  
Relaxation Processes ◽  
Flow Problems ◽  
Shock Mach Number ◽  
Ionizing Gases ◽  
End Wall

Abstract Numerical calculations have been made about shock reflection processes in ionizing argon on the end wall of a shock: tube. The two-step Lax-Wendroff scheme was employed to solve time-dependent one-dimensional inviscid flow problems for ionizing gases. Complicated flowfields were found to occur due to interactions between ionization relaxation processes and reflected shocks. Calculations were performed for three cases: incident-shock Mach number M s = 16 and initial pressure p1 = 1 torr; Ms = 14 and p1 = 3 torr; M s = 12 and p1 = 5 torr.

Measurements of Decompression Wave Speed in Natural Gas Containing 2-8% (Mole) Hydrogen by a Specialized Shock Tube

2016 ◽  
Author(s):  
K. K. Botros ◽  
S. Igi ◽  
J. Kondo
Keyword(s):  
Natural Gas ◽  
Shock Tube ◽  
Hydrogen Concentration ◽  
Wave Speed ◽  
Accurate Determination ◽  
Initial Pressure ◽  
Propagation Speed ◽  
Wave Speeds ◽  
Decompression Wave ◽  
Curve Method

The Battelle two-curve method is widely used throughout the industry to determine the required material toughness to arrest ductile (or tearing) pipe fracture. The method relies on accurate determination of the propagation speed of the decompression wave into the pipeline once the pipe ruptures. GASDECOM is typically used for calculating this speed, and idealizes the decompression process as isentropic and one-dimensional. While GASDECOM was initially validated against quite a range of gas compositions and initial pressure and temperature, it was not developed for mixtures containing hydrogen. Two shock tube tests were conducted to experimentally determine the decompression wave speed in lean natural gas mixtures containing hydrogen. The first test had hydrogen concentration of 2.88% (mole) while the second had hydrogen concentration of 8.28% (mole). The experimentally determined decompression wave speeds from the two tests were found to be very close to each other despite the relatively vast difference in the hydrogen concentrations for the two tests. It was also shown that the predictions of the decompression wave speed using the GERG-2008 equation of state agreed very well with that obtained from the shock tube measurements. It was concluded that there is no effects of the hydrogen concentration (between 0–10% mole) on the decompression wave speed, particularly at the lower part (towards the choked pressure) of the decompression wave speed curve.

Shock-Tube Performance at Low Initial Pressure

1959 ◽  
Vol 2 (2) ◽  
pp. 207 ◽  
Author(s):  
Russell E. Duff
Keyword(s):  
Shock Tube ◽  
Initial Pressure

Numerical Simulation for Inert Gas Stimulated by Explosion of Solid Propellant Emitting Visible Light

2013 ◽  
Vol 325-326 ◽  
pp. 200-203
Author(s):  
Jia Guo ◽  
Yu Shu Xie ◽  
Jun Fang ◽  
Chen Zheng ◽  
Li Feng Xie
Keyword(s):  
Visible Light ◽  
Energy Intensity ◽  
Initial Pressure ◽  
Radiation Energy ◽  
Light Energy ◽  
Dynamic Responses ◽  
Inert Gas ◽  
Solid Propellants ◽  
The Stability ◽  
Peak Value

In this paper, dynamic responses on radiation energy intensity of inert gas are simulated in use of software ANSYS / LS-DYNA when inert gas is stimulated by explosion of solid propellants to emit visible light. The effects for the visible light energy intensity emitted by inert gas are analyzed on different initial pressures in the inert gas container and with different igniting methods by propellants. Simulation results show that, the bigger initial pressure in the container is, the higher the peak value of visible light energy density intensity is and the better the effect of the visible light emitted by inert gas is. There are fewer effects on the peak value of visible light energy intensity emitted by inert gas with different igniting methods. However, it has an impact on the stability when inert gas emitting visible light. The stability is the best when central point of the propellant column is ignited.

Mikrowellenmessungen der Elektronendichte und -stoßfrequenz in elektromagnetisch erzeugten Stoßwellen

1966 ◽  
Vol 21 (12) ◽  
pp. 2040-2046
Author(s):  
W. Makios
Keyword(s):  
Shock Front ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Discharge Plasma ◽  
Collision Frequency ◽  
Initial Pressure ◽  
Electron Collision ◽  
Microwave Measurements ◽  
Electron Collision Frequency ◽  
Microwave Transmission

Microwave measurements were made of the electron density and the electron collision frequency in the plasma between the shock front and the discharge plasma of electromagnetically produced shock waves. These investigations were carried out in argon and hydrogen at po=2 mm Hg initial pressure and velocities ranging from M=5 to M=20. At higher velocities the discharge plasma advances right into the shock front. A 4-mm-microwave transmission interferometer was used. A system of LECHER wires in the measuring arm of the interferometer provided a spatial resolution of approximately 1 to 2 mm and proved successful in measuring the electron density distribution between the shock front and the following discharge plasma. In the case of hydrogen the rise of the electron density in the shock front is caused by compression of the precursor electrons. In argon, on the other hand, most of the electrons are produced behind the shock front. A typical relaxation of the electron density towards equilibrium was measured. It was also possible to measure the electron collision frequency in argon as a function of time (and hence of the distance from the shock front).

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