Apparatus for generating high frequency shock waves provided with a screen which reduces the electric leakages

1989 ◽  
Vol 86 (3) ◽  
pp. 1210-1210
Author(s):  
Jean‐Louis Mestas ◽  
Dominique Cathignol
Keyword(s):  
Shock Waves ◽  
High Frequency

scholarly journals May 24, 1968 at Inangahua Junction

1969 ◽  
Vol 2 (1) ◽  
pp. 37-38
Author(s):  
T. Hogue
Keyword(s):  
Shock Waves ◽  
High Frequency ◽  
Initial Displacement ◽  
North East ◽  
The North ◽  
Upward Displacement ◽  
The Town

The twin communities of Inangahua Camp and Inangahua Junction were rudely awakened at approximately 5.25 a.m.by a severe earthquake. About a minute before the quake all the birdlife suddenly stopped their noisy callingand an uncanny stillness settled over the area. The first movement of the earthquake was an upward displacement although a few argue that the initial displacement was to the north east. No longer than two seconds later the high frequency vibrating and confusion of noise enveloped the town, then came the jolting of no discriminate pattern as shock-waves started to rebound through the region. During the peak of the earthquake most people who. were by now fully awakened thought that "this was the end", any dissenters from this view acknowledged that it was "at least a beaut”.

On the effectiveness of ventilation to mitigate the damage of spherical membrane vessels subjected to internal detonations

2020 ◽  
Vol 11 (3) ◽  
pp. 319-339
Author(s):  
Francisco Hernandez ◽  
Xihong Zhang ◽  
Hong Hao
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
High Frequency ◽  
Arrival Time ◽  
Time Lag ◽  
Reflected Shock Wave ◽  
High Explosives ◽  
Element Analysis ◽  
Blast Overpressure ◽  
Reflected Shock

This article conducts a comparative study on the effectiveness of ventilation to mitigate blasting effects on spherical chambers subjected to internal detonations of high explosives through finite element analysis using the software package AUTODYN. Numerical simulations show that ventilation is ineffective in mitigating the damage of spherical chambers subjected to internal high explosives explosions because the chamber response is mainly described by high-frequency membrane modes. Openings do not reduce the chamber response despite they can reduce the blast overpressure after the chamber reaches its peak response. Worse still, openings lead to stress concentration, which weakens the structure. Therefore, small openings may reduce the capacity of the chamber to resist internal explosions. In addition, because large shock waves impose the chamber to respond to a reverberation frequency associated with the re-reflected shock wave pulses, secondary re-reflected shock waves can govern the chamber response, and plastic/elastic resonance can occur to the chamber. Simulations show that the time lag between the first and the second shock wave ranges from 3 to 7 times the arrival time of the first shock wave, implying that the current simplified design approach should be revised. The response of chambers subjected to eccentric detonations is also studied. Results show that due to asymmetric explosions, other membrane modes may govern the chamber response and causes localized damage, implying that ventilation is also ineffective to mitigate the damage of spherical chambers subjected to eccentric detonations.

Experimental research of high frequency properties of plasma and magnetohydrodynamic shock waves

1958 ◽  
Vol 7 (3-4) ◽  
pp. 299
Author(s):  
K.D. Sinelnicov ◽  
P.M. Zeidlic ◽  
Ja.B. Fainberg ◽  
A.M. Nerkashevich ◽  
O.G. Zavgorodnov ◽  
...  
Keyword(s):  
Shock Waves ◽  
Experimental Research ◽  
High Frequency ◽  
Magnetohydrodynamic Shock ◽  
Frequency Properties

The Shockwave Response of Thin Composite Materials

2012 ◽  
Author(s):  
Douglas Jahnke ◽  
Yiannis Andreopoulos
Keyword(s):  
Composite Materials ◽  
Shock Waves ◽  
Shock Tube ◽  
Frequency Response ◽  
High Frequency ◽  
Composite Plates ◽  
Image Correlation ◽  
Flat Plates ◽  
High Frequency Response ◽  
Nominal Thickness

Impingement of blast or shock waves on structures is characterized by a substantial transient aerodynamic load that develops over the short time associated with the shock reflection time scale. This mutual interaction between the shock wave and the structure can cause significant deformation of the structure and high strain rates within the material resulting in damage. An experimental investigation was carried out to determine the aeroelastic response of thin flat plates of composite materials during face-on impact with planar shock waves. The experiments were performed in a large-scale shock tube research facility, which had a working section of 12 inches in diameter and a length of 80 ft. Phenolic composite S2-HJ1 plates of 1/8 inch nominal thickness consisting of 12 layers of fibers and epoxy composite S2 plates of 1/8 inch nominal thickness consisting of 10 layers of fibers were tested in the present investigation. Miniature semi-conductor strain-gauges of high frequency response, high speed photography and Digital Image Correlation techniques were employed to measure locally the strain on the exterior side of the plates and high frequency response pressure transducers were used to measure time-dependent wall and total pressure. In order to provide comparison with the response of monolithic material to similar compressive loadings, aluminum and stainless steel plates were also tested under the same conditions. The application of shock loading on the specimen causes significant permanent deformation on the plates which has been measured immediately after the experiment while the specimen is still mounted on the end flange of the shock tube. These experimental data obtained in the present experiments include the measured displacement of the external surface of the plates from their original position in the normal to the plate direction along the radius of the specimen. This displacement is highest at the center of the plate and zero at the location of clamping. The results show that the deformations of the thicker plates are still considerably lower than those obtained in the steel and thinner composite plates although the loading pressure is more than triple in magnitude and the corresponding impulse is about 2.3 times higher. Composite plates were found to suppress several of the modes of the wave patterns while metallic ones demonstrate a rich variety of interacting modes. The frequency content of the strain signals on the surface of composite plates was not always the same with the content of the surface acceleration measured in free vibration experiments.

Inverse Energy Cascade of Fast Magnetosonic Turbulence in the Heliosheath

2020 ◽  
Author(s):  
Bertalan Zieger
Keyword(s):  
Solar Wind ◽  
High Resolution ◽  
Shock Waves ◽  
High Frequency ◽  
Collisionless Plasma ◽  
Energy Cascade ◽  
Fast Mode ◽  
Turbulence Spectrum ◽  
Inverse Energy Cascade ◽  
Voyager 2

<p>The solar wind in the heliosheath beyond the termination shock (TS) is a non-equilibrium collisionless plasma consisting of thermal solar wind ions, suprathermal pickup ions (PUI) and electrons. In such multi-ion plasma, two fast magnetosonic wave modes exist: the low-frequency fast mode that propagates in the thermal ion component and the high-frequency fast mode that propagates in the suprathermal PUI component [<em>Zieger et al.</em>, 2015]. Both fast modes are dispersive on fluid and ion scales, which results in nonlinear dispersive shock waves. In this talk, we briefly review the theory of dispersive shock waves in multi-ion collisionless plasma. We present high-resolution three-fluid simulations of the TS and the heliosheath up to 2.2 AU downstream of the TS. We show that downstream propagating nonlinear magnetosonic waves grow until they steepen into shocklets (thin current sheets), overturn, and start to propagate backward in the frame of the downstream propagating wave, as predicted by theory <em>[McKenzie et al</em>., 1993; <em>Dubinin et al.</em>, 2006]. The counter-propagating nonlinear waves result in fast magnetosonic turbulence far downstream of the shock. Since the high-frequency fast mode is positive dispersive on fluid scale, energy is transferred from small scales to large scales (inverse energy cascade). Thermal solar wind ions are preferentially heated by the turbulence. Forward and reverse shocklets in the heliosheath can efficiently accelerate both ions and electrons to high energies through the shock drift acceleration mechanism. We validate our three-fluid simulations with in-situ high-resolution Voyager 2 magnetic field and plasma observations at the TS and in the heliosheath. Our simulations reproduce the magnetic turbulence spectrum with a spectral slope of -5/3 observed by Voyager 2 in frequency domain [<em>Fraternale et al</em>., 2019]. However, since Taylor’s hypothesis is not true for fast magnetosonic perturbations in the heliosheath, the inertial range of the turbulence spectrum is not a Kolmogorov spectrum in wave number domain. </p>

The structure of hydromagnetic shock waves

1971 ◽  
Vol 5 (2) ◽  
pp. 177-197 ◽  
Author(s):  
R. J. Bickerton ◽  
L. Lenamon ◽  
R V. W. Murphy
Keyword(s):  
Shock Waves ◽  
High Frequency ◽  
Transport Coefficients ◽  
Mean Free Path ◽  
Fine Scale ◽  
Collisionless Shocks ◽  
Fluid Approximation ◽  
Effective Transport ◽  
Effective Transport Coefficients ◽  
Two Fluid

We discuss the structure of hydomagnetic shock waves of various types. The plasma is treated in the two fluid approximation and coffisional transport coefficients are used. This treatment should be valid in a collisional plasma subject to the usual caveat about the use of transport coefficients in situations where the density, temperature, etc., may change significantly over a mean free path. The approach may also have some validity for collisionless shocks if the dissipation mechanisms involve instabilities of sufficiently fine scale and high frequency that they can be described by effective transport coefficients.

Simulation of the Effects of Shock Wave Passing on a Turbine Rotor Blade

1985 ◽  
Vol 107 (4) ◽  
pp. 998-1006 ◽  
Author(s):  
D. J. Doorly ◽  
M. L. G. Oldfield
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Shock Waves ◽  
High Frequency ◽  
Guide Vane ◽  
Turbine Rotor ◽  
Surface Boundary ◽  
Suction Surface ◽  
Very High Frequency ◽  
And Shock Waves

The unsteady effects of shock waves and wakes shed by the nozzle guide vane row on the flow over a downstream turbine rotor have been simulated in a transient cascade tunnel. At conditions representative of engine flow, both wakes and shock waves are shown to cause transient turbulent patches to develop in an otherwise laminar (suction-surface) boundary layer. The simulation technique employed, coupled with very high-frequency heat transfer and pressure measurements, and flow visualization, allowed the transition initiated by isolated wakes and shock waves to be studied in detail. On the profile tested, the comparatively weak shock waves considered do not produce significant effects by direct shock-boundary layer interaction. Instead, the shock initiates a leading edge separation, which subsequently collapses, leaving a turbulent patch that is convected downstream. Effects of combined wake- and shock wave-passing at high frequency are also reported.

scholarly journals The new model of erosion destroying

2019 ◽  
Vol 489 (6) ◽  
pp. 581-584
Author(s):  
V. T. Kuzavov
Keyword(s):  
Shock Waves ◽  
Experimental Model ◽  
Solid Surface ◽  
High Frequency ◽  
Acoustic Energy ◽  
Erosion Damage ◽  
New Model ◽  
Cavitation Effect ◽  
Cumulative Jets ◽  
Spiral Structures

A new physical (experimental) model of cavitation destruction of the studied materials is proposed. In the mo-dern model of the cavitation effect, the destruction of materials is associated with the impacts of cumulative jets, which are formed during the asymmetric slamming of cavitation bubbles near the solid surface and the shock waves that occur during their compression. In the new model, erosion damage is explained by the formation of cavitation tubes (с-tubes) with a spiral high-frequency structure in the materials under study that were previously unknown in the literature. The destruction of materials is associated with the focusing of acoustic energy along the axis of the spiral structures. When focusing energy, there is a significant increase in pressure and temperature along the axis of the spiral structures, which leads to the destruction of the materials under study.

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