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

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.

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).

Interferometrische Untersuchungen an elektromagnetisch beschleunigten Stoßwellen II

1967 ◽  
Vol 22 (4) ◽  
pp. 438-443
Author(s):  
H. Brinkschulte
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Shock Front ◽  
Time Dependence ◽  
Discharge Plasma ◽  
Initial Pressure ◽  
Homology Theory ◽  
Density Jump ◽  
Current Pulses ◽  
Steady Shock

The shock waves produced in T-tubes were investigated with a MACH-ZEHNDER interferometer. The experiments were conducted in hydrogen at an initial pressure of 5 torr. A power crowbar arrangement was used to produce single current pulses. These caused single shock waves to occur with every discharge. Reproducible, non-steady shock waves separated from the discharge plasma were observed at MACH numbers M < 15. By measuring the time dependence of the velocity of the shock front over the entire length of the tube (60 cm) it was found that the shock front behaves in accordance with the homology theory of v. WEIZSÄCKER. From the interferograms it is also possible to determine (but only qualitatively) the drop in density immediately behind the front. As the density jump increases, this drop becomes steeper and steeper—again in agreement with the theory. Moreover, it was shown by side-on photographs taken at various distances from the electrodes that the shock front becomes plane once the shock wave has covered a path ten times longer than the tube diameter.

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.

Mikrowelleninterferometrie an elektromagnetisch erzeugten Stoßwellen

1965 ◽  
Vol 20 (7) ◽  
pp. 870-875
Author(s):  
W. Makios ◽  
H. Muntenbruch
Keyword(s):  
Shock Waves ◽  
Shock Front ◽  
Doppler Effect ◽  
Initial Pressure ◽  
Simple Construction ◽  
Velocity Measurements ◽  
T Tube ◽  
The Doppler Effect ◽  
Mach 10 ◽  
Made In

Velocity measurements of electron front in electromagnetically generated T-tube shock waves, have been made with 4 mm microwaves using the DOPPLER effect. The measurements were made in hvdrogen at an initial pressure of 1 to 5 torr. The shockfront velocity was between Mach 5 and Mach 20. It is shown that the reflection of microwaves occurs at the luminous front at low velocities, at the shock front at higher velocities. There is a region in between (at about Mach 10) where a reflection takes place at both fronts. For this case the electron density in the shock front can be determined within a factor of 2. For these investigations a microwave interferometer of simple construction was developed. This interferometer is fully described.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

The Numerical Modeling of Spherical Explosion in the Foam

2016 ◽  
Vol 11 (1) ◽  
pp. 60-65 ◽  
Author(s):  
R.Kh. Bolotnova ◽  
E.F. Gainullina
Keyword(s):  
Shock Wave ◽  
Numerical Modeling ◽  
Initial Pressure ◽  
Water Volume ◽  
Symmetric Model ◽  
Two Phase ◽  
Experimental Conditions ◽  
Initial Water ◽  
Aqueous Foam ◽  
Spherical Explosion

The spherical explosion propagation process in aqueous foam with the initial water volume content α10=0.0083 corresponding to the experimental conditions is analyzed numerically. The solution method is based on the one-dimensional two-temperature spherically symmetric model for two-phase gas-liquid mixture. The numerical simulation is built by the shock capturing method and movable Lagrangian grids. The amplitude and the width of the initial pressure pulse are found from the amount of experimental explosive energy. The numerical modeling results are compared to the real experiment. It’s shown, that the foam compression in the shock wave leads to the significant decrease in velocity and in amplitude of the shock wave.

scholarly journals Unusual enhancement of ~ 30 MeV proton flux in an ICME sheath region

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Mitsuo Oka ◽  
Takahiro Obara ◽  
Nariaki V. Nitta ◽  
Seiji Yashiro ◽  
Daikou Shiota ◽  
...  
Keyword(s):  
Shock Front ◽  
Energetic Particle ◽  
Leading Edge ◽  
Solar Energetic Particle ◽  
Interplanetary Shock ◽  
Proton Event ◽  
Sheath Region ◽  
Time Profiles ◽  
Energetic Particle Flux ◽  
Mev Protons

AbstractIn gradual Solar Energetic Particle (SEP) events, shock waves driven by coronal mass ejections (CMEs) play a major role in accelerating particles, and the energetic particle flux enhances substantially when the shock front passes by the observer. Such enhancements are historically referred to as Energetic Storm Particle (ESP) events, but it remains unclear why ESP time profiles vary significantly from event to event. In some cases, energetic protons are not even clearly associated with shocks. Here, we report an unusual, short-duration proton event detected on 5 June 2011 in the compressed sheath region bounded by an interplanetary shock and the leading edge of the interplanetary CME (or ICME) that was driving the shock. While < 10 MeV protons were detected already at the shock front, the higher-energy (> 30 MeV) protons were detected about four hours after the shock arrival, apparently correlated with a turbulent magnetic cavity embedded in the ICME sheath region.

Sign in / Sign up

Export Citation Format

Share Document