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.

Interferometrische Untersuchungen an elektromagnetisch beschleunigten Stoßwellen

1965 ◽  
Vol 20 (2) ◽  
pp. 196-202 ◽  
Author(s):  
H. Brinkschulte ◽  
H. Muntenbruch
Keyword(s):  
Shock Waves ◽  
Shock Front ◽  
Discharge Plasma ◽  
Shock Velocity ◽  
Computational Method ◽  
Density Jump ◽  
Precursor Effects ◽  
Shock Fronts ◽  
Selection Of ◽  
Made In

The phenomena of shock waves generated electromagnetically in T-tubes were studied with a MACH-ZEHNDER interferometer. The measurements were made in hydrogen at initial pressures from 2.5 to 10 mm Hg. Shock velocity varied between Mach 6 and Mach 20. It was found that there are two fronts: the luminousity front due to the discharge plasma and the non-luminous shock front in front of this. The distance between the shock front and the luminousity front decreases with increasing velocity. At vs ⍙ Mach 20 the luminousity front reaches the shock front. Shock fronts are always plane. The density decreases directly behind the shock front. The shock waves thus formed cannot be described with the RANKINE-HUGONIOT equations. At small velocities, the density jump is 6, at higher velocities the gas is dissociated. The refractive index of atomic hydrogen can be measured. Simultaneously the selection of the computational method used to describe the shock conditions in hydrogen can be justified. Precursor effects have no influence, relaxations could not be seen.

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.

scholarly journals Shock Waves Propagation in the Turbulent Interplanetary Plasma

1996 ◽  
Vol 154 ◽  
pp. 23-28
Author(s):  
I.V. Chashei ◽  
V.I. Shishov
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Shock Front ◽  
Interplanetary Shock ◽  
Energy Losses ◽  
Strong Turbulence ◽  
Background Turbulence ◽  
Interplanetary Plasma ◽  
Waves Propagation

AbstractEffect of turbulence on interplanetary shock waves propagation is considered. It is shown that background turbulence results in the additional shock wave deceleration which may be comparable with the deceleration due to plasma sweeping. The turbulent deceleration is connected with the energy losses due to the strong turbulence amplification behind the moving shock front.

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).

Direct numerical simulation of isotropic turbulence interacting with a weak shock wave

1993 ◽  
Vol 251 ◽  
pp. 533-562 ◽  
Author(s):  
Sangsan Lee ◽  
Sanjiva K. Lele ◽  
Parviz Moin
Keyword(s):  
Shock Wave ◽  
Kinetic Energy ◽  
Shock Waves ◽  
Shock Front ◽  
Numerical Simulations ◽  
Turbulent Kinetic Energy ◽  
Isotropic Turbulence ◽  
Weak Shock ◽  
Linear Analysis ◽  
Weak Shock Wave

Interaction of isotropic quasi-incompressible turbulence with a weak shock wave was studied by direct numerical simulations. The effects of the fluctuation Mach number Mt of the upstream turbulence and the shock strength M21 — 1 on the turbulence statistics were investigated. The ranges investigated were 0.0567 ≤ Mt ≤ 0.110 and 1.05 ≤ M1 ≤ 1.20. A linear analysis of the interaction of isotropic turbulence with a normal shock wave was adopted for comparisons with the simulations.Both numerical simulations and the linear analysis of the interaction show that turbulence is enhanced during the interaction with a shock wave. Turbulent kinetic energy and transverse vorticity components are amplified, and turbulent lengthscales are decreased. The predictions of the linear analysis compare favourably with simulation results for flows with M2t < a(M21 — 1) with a ≈ 0.1, which suggests that the amplification mechanism is primarily linear. Simulations also showed a rapid evolution of turbulent kinetic energy just downstream of the shock, a behaviour not reproduced by the linear analysis. Investigation of the budget of the turbulent kinetic energy transport equation shows that this behaviour can be attributed to the pressure transport term.Shock waves were found to be distorted by the upstream turbulence, but still had a well-defined shock front for M2t < a(M21— 1) with a ≈ 0.1). In this regime, the statistics of shock front distortions compare favourably with the linear analysis predictions. For flows with M2t > a(M21— 1 with a ≈ 0.1, shock waves no longer had well-defined fronts: shock wave thickness and strength varied widely along the transverse directions. Multiple compression peaks were found along the mean streamlines at locations where the local shock thickness had increased significantly.

scholarly journals Magnetohydrodynamic Ionizing Shock Waves in a Conducting Medium

1965 ◽  
Vol 18 (4) ◽  
pp. 363 ◽  
Author(s):  
B Green ◽  
RM May
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Shock Waves ◽  
Field Strength ◽  
Shock Front ◽  
Ionization Energy ◽  
Conducting Medium ◽  
Flow Parameters ◽  
Magnetohydrodynamic Shock ◽  
Initial Magnetic Field

We present numerical calculations for the flow parameters (velocity, density, pressure, etc.) in a magnetohydrodynamic shock wave propagating in a conducting medium. The effect of ionization in the shock front is included. The results are presented graphically for a complete range of the initial magnetic field strength and direction, and for several arbitrary values of the ionization energy of the downstream fluid.

The Mechanism of Three-Dimension Steady Shock Wave Interaction

2018 ◽  
Author(s):  
Chun Wang ◽  
Ruixin Yang ◽  
Zonglin Jiang
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Shock Waves ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Local Heat ◽  
Three Dimension ◽  
Complex Flow ◽  
Shock Wave Interaction ◽  
Steady Shock

The problem of three-dimensional steady shock wave interaction is a key issue for supersonic and hypersonic corner flow. Due to the complexity of shock configurations, there is no analytical theory to such problem and the mechanism of three-dimensional shock waves and boundary layer interaction has not been clearly known. In this paper, an analytical approach to the problem of three-dimensional steady shock wave interaction was exhibited to analytically interpret the mechanism of three-dimensional interaction of two oblique planar shock waves. The results showed that the problem of three-dimensional steady shock wave interaction could be transformed to that of two moving shock wave interaction in two-dimensional plane, and there are various interaction configurations such as regular interaction, Mach interaction and weak interaction. The mechanism of three-dimensional shock wave interaction is helpful to understand the complex flow mechanism induced by three-dimensional shock wave and boundary layer in hypersonic flow. The interaction of three-dimensional shock waves and boundary layer plays important role in the complex flow feature in hypersonic rudder region. The contact surface induced by three-dimensional shock waves represents a local jet. When the flow jet impinges on the boundary layer of wall surface, the jet makes the boundary layer thinner and will inevitably cause local heat flux peak. The interaction configurations of three-dimensional shock wave play important role in the gasdynamic heating mechanisms of hypersonic complex flow.

scholarly journals Hydrodynamic evolution of laser driven diverging shock waves

1990 ◽  
Vol 8 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
M. A. Harith ◽  
V. Palleschi ◽  
A. Salvetti ◽  
D. P. Singh ◽  
G. Tropiano ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Temporal Evolution ◽  
Laser Energy ◽  
Appreciable Effect ◽  
Density Jump ◽  
Hydrodynamic Evolution ◽  
Self Similar Solution ◽  
Glass Cell ◽  
Strong Explosion

Spherically symmetric shock waves have been produced via Nd3+ laser induced break-down in helium, nitrogen and air at pressures ranging from 760 Torr to 2300 Torr. The measurements are performed at different absorbed laser energies (E0 = 0.05 J to 2 J) at the center of the experimental spherical glass cell where the breakdown of the gas takes place. The temporal evolution of the shock wave followed by a double-pulse, doublewavelength holographic technique is described hydrodynamically well by the point strong explosion theory. The ambient gas counterpressure plays a negligible role in determining the shock wave motion even at low laser energy absorption (E0 ≤, 0.5 J), whereas it has an appreciable effect on the gas density jump at the shock wave itself. The experimental data on temporal evolution of the density jump of the gas and the corresponding theoretical profiles obtained adopting a non-self-similar solution at the same laser absorbed energy are found to be in good mutual agreement.

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.

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