scholarly journals Entanglement wedge cross-section in shock wave geometries

2020 ◽  
Vol 2020 (7) ◽  
Author(s):  
Jan Boruch
Keyword(s):  
Shock Wave ◽  
Cross Section

Experimental and Numerical Investigation of Shock Wave Attenuation by Dynamic Barriers

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Shahar Berger ◽  
Gabi Ben-Dor ◽  
Oren Sadot
Keyword(s):  
Shock Wave ◽  
Blast Wave ◽  
Cross Section ◽  
Wave Attenuation ◽  
Pressure Jump ◽  
Ongoing Research ◽  
Rigid Barrier ◽  
Shock Wave Attenuation ◽  
Opening Ratio ◽  
Barrier Opening

An explosion at the entrance of an underground bunker and a suicide bomber inside an airplane are examples of scenarios in which blast waves propagate in tunnels and corridor-type structures. The need to attenuate the shock/blast wave propagating downstream a corridor and mitigate the developed loads inside the structure is essential. The interaction of a shock/blast wave with an obstacle inside a tunnel can dramatically reduce its strength. Earlier researches revealed that the dominant parameter in attenuating a shock wave by rigid barriers is the barrier opening ratio (i.e., the cross section that is open to the flow divided by the total cross section of the tunnel). Decreasing the opening ratio from 0.6 to 0.2 increased the attenuation by about 40%. Based on strong dependence of the attenuation on the opening ratio, a barrier designed to adjust its opening ratio to the loads exerted upon it is essential. In our previous study, we found that the effect of the rigid barrier geometry becomes more significant when the barrier inclination angle is larger, i.e., the barriers inclined toward the oncoming shock wave were found to be more effective in reducing the transmitted shock wave intensity than those inclined in the opposite direction. The pressure difference between both sides of the barrier exerts massive loads on the barrier. In the present ongoing research, based on a numerical approach using a commercial solver (msc.dytran), we focus on the geometry of a dynamic barrier, which changes its orientation as a response to the loads exerted on it. As a result, the barrier opening ratio, which as mentioned earlier strongly affects the shock wave attenuation, changes too. In this study, the feasibility of a dynamic barrier and the complex flow regime around it are investigated. The rapid pressure drop downstream of the barrier depends both on the shock wave strength and the barrier material and geometrical properties. Barriers with various geometries and properties are used to investigate the concept of a deflecting/rotating barrier as a response to the shock wave loads exerted upon it. For the first time, a new and exciting proven concept of a dynamic barrier, which reacts to the loads exerted upon it from a passing shock wave, and dramatically reduces the shock-induced pressure jump downstream of the barrier, is demonstrated.

An Experimental and CFD Investigation of a Supersonic Nonisobaric Jet Exhausting From a Beveled Nozzle

2014 ◽  
Vol 9 (2) ◽  
pp. 75-83
Author(s):  
Valeriy Zapryagaev ◽  
Ivan Kavun ◽  
Sergey Kundasev
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Cross Section ◽  
Qualitative Agreement ◽  
Supersonic Jet ◽  
Wave Structure ◽  
Shock Wave Structure ◽  
Ansys Fluent

The aim of the investigation is to understand the shock-wave structure of the supersonic jet exhausting from a beveled nozzle. Results of investigation are presented as cross section Pitotpressure fields. This data can be used for verification of CFD results. The experiment was complemented by numerical simulation with using of the program packet ANSYS Fluent. The satisfactory qualitative agreement was obtained

A note on shock flow in a channel

1958 ◽  
Vol 4 (5) ◽  
pp. 501-504 ◽  
Author(s):  
Roy Gundersen
Keyword(s):  
Shock Wave ◽  
Closed Form ◽  
Cross Section ◽  
Shock Strength ◽  
Piston Motion

A shock wave is generated by a uniform compressive piston motion and passes into a channel of slowly varying cross-section. A relation in closed form is obtained between shock strength and the area of the channel and is used to discuss converging cylindrical and spherical shocks.

Thickness and volume measurements of a Richtmyer–Meshkov instability-induced mixing zone in a square shock tube

1997 ◽  
Vol 349 ◽  
pp. 67-94 ◽  
Author(s):  
G. JOURDAN ◽  
L. HOUAS ◽  
J.-F. HAAS ◽  
G. BEN-DOR
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Cross Section ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Mixing Zone ◽  
Laser Absorption ◽  
Shock Wave Mach Number ◽  
Atwood Number ◽  
Absorption Technique

A simultaneous three-directional laser absorption technique for the study of a shock-induced Richtmyer–Meshkov instability mixing zone is reported. It is an improvement of a CO2 laser absorption technique, using three detectors during the same run, through three different directions of the test section, for the simultaneous thickness measurement of the mixing zone near the corner, near the wall and at the centre of a square-cross-section shock tube. The three-dimensional mean front and rear shapes of the mixing zone, its thickness and volume are deduced from the experimental measurements. The cases when the shock wave passes from a heavy gas to a light one, from one gas to another of similar densities and from a light gas to a heavy one, are investigated before and after the mixing zone compression by the reflected shock, for different incident shock wave Mach numbers. It is shown that the mixing zone is strongly deformed by the wall boundary layer when it becomes turbulent. Consequently, the thickness of the mixing zone is not constant along the shock tube cross-section, and the measurement of the mean volume of the mixing zone appears to be more appropriate than its mean thickness at the centre of the shock tube. The influence of the incident shock wave Mach number is also studied. When the Atwood number tends to zero, we observe a limit-like regime and the thickness, or the volume, of the mixing zone no longer varies with the incident shock wave Mach number. Furthermore, a series of experiments undertaken with an Atwood number close to zero enabled us to define a membrane-induced minimum mixing thickness, L0, depending on the initial configuration of the experiments. From the experimental data, a hypothesis about the mixing zone thickness evolution law with time is deduced on the basis of L0. The results are found to follow two very different laws depending on whether they are considered before or after the establishment of the plenary turbulent regime. However, no general trend can be determined to describe the entire phenomenon, i.e. from the initial conditions until the turbulent stage.

Numerical Investigation of Shock Wave Attenuation by Geometrical Means: Double Barrier Configuration

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Shahar Berger ◽  
Gabi Ben-Dor ◽  
Oren Sadot
Keyword(s):  
Shock Wave ◽  
Blast Wave ◽  
Cross Section ◽  
Inclination Angle ◽  
Wave Attenuation ◽  
Geometrical Parameters ◽  
Double Barrier ◽  
Shock Wave Attenuation ◽  
Opening Ratio ◽  
Two Barriers

Due to the increase in global terror threats, many resources are being invested in efforts to find and utilize efficient protective means and technologies against blast waves induced by conventional and nonconventional weapons. Bombs exploding in the entrance of military underground bunkers initiate a blast wave that propagates in a corridor-type structure causing injuries to human and damage both to the structures and the equipment. Rigid barriers of different geometries inside a tunnel can cause the blast wave to diffract and attenuate, leaving behind it a complex flow field that changes the impact on the target downstream of the barrier. In our earlier phase of the research that dealt with a single barrier configuration, it was shown that the opening ratio (i.e., the cross section that is open to the flow divided by the total cross section of the tunnel) is the most dominant parameter in attenuating the shock wave. Additionally, it was found that when the opening ratio was fixed at 0.375, the barrier inclination angle was significantly more effective than the barrier width in attenuating the shock wave. The present phase of the research focuses on the dependence of the shock wave attenuation on a double barrier configuration, while keeping the opening ratio fixed at 0.375. The methodology is a numerical approach that has been validated by experimental results. The experiments were conducted in a shock tube using a high-speed camera. The numerical simulations were carried out using a commercial code based on an MSC-DYTRAN solver under initial conditions similar to those in the experiments. A wide span of the barrier geometrical parameters was used to map in a continues manner the effect of the barrier geometry on the shock wave attenuation. By analyzing the geometrical parameters characterizing the double barrier configuration, better understanding of the physical mechanisms of shock wave attenuation is achieved. It was shown that for a double barrier configuration, the first barrier inclination angle was very dominant in attenuating the shock wave, as expected, while the efficiency of the second barrier inclination angle depended on the distance between the two barriers. Only when the distance between the two barriers was increased and the second barrier was far enough from the first barrier, it affected the attenuation regardless of the first barrier.

scholarly journals Formation of a Double-Layer Ultrafine Crystal Structure for High-Current Pulsed Electron Beam-Treated Al–20Si–5Mg Alloy

Coatings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 413 ◽  
Author(s):  
Bo Gao ◽  
Kui Li ◽  
Pengfei Xing
Keyword(s):  
Crystal Structure ◽  
Shock Wave ◽  
Electron Beam ◽  
Thermal Stress ◽  
Cross Section ◽  
Stress Wave ◽  
Double Layer ◽  
Heat Affected Zone ◽  
High Current ◽  
Pulsed Electron Beam

In this paper, the effect of high-current pulsed electron beam (HCPEB) on the microstructure refinement of an Al–20Si–5Mg alloy in the cross-section modified zone was studied, and a double-layer ultrafine crystal structure of the Al–20Si–5Mg alloy was formed. It was found that the cross-section modified zone was divided into three zones, namely, the remelted layer, the heat-affected zone, and the thermal stress wave-affected zone after HCPEB treatment. For the remelted layer, metastable structures were formed due to the rapid heating and cooling rates. For the heat-affected zone, the grain of the aluminum phase was refined due to the cooperative effects of shock wave (formed during an eruption event of the brittle phase), thermal-stress wave (formed during thermal expansion of the alloy surface), and quasi-static thermal stress (formed as a result of an unevenly distributed temperature gradient in the inner material) at high temperatures. For the thermal stress wave-affected zone, the grain refinement was not obvious due to the decreasing energy of the shock wave and the thermal-stress wave at low temperatures. In addition, firm evidence for the tracing of shock waves in the heat-affected zone was demonstrated for the first time and verified for the founding of the broken acicular eutectic silicon. Through this experiment, the mechanical properties of Al–20Si–5Mg alloy materials in both the remelted layer and heat-affected zone were significantly improved after HCPEB treatment.

Die spezifische Verbreiterung der FeI-Resonanzlinie 3859,91 Å durch Stöße mit Argonatomen bei hohen Temperaturen / Specific Line-Broadening of the Iron-Resonance-Line 3859,91 Å by Collisions with Argon Atoms at high Temperatures

1980 ◽  
Vol 35 (8) ◽  
pp. 828-831 ◽  
Author(s):  
J. Steinwandel ◽  
V. E. Joos ◽  
M. Hauser ◽  
Th. Dietz
Keyword(s):  
Shock Wave ◽  
Cross Section ◽  
Resonance Line ◽  
Reflected Shock Wave ◽  
Thermodynamic Quantities ◽  
Line Broadening ◽  
Unimolecular Decomposition ◽  
Reflected Shock ◽  
Collision Partner ◽  
Specific Line

AbstractThe specific line-broadening cross section of the FeI-resonance transition at 3859.91 Å by collision with argon atoms was measured in the temperature range of 2000 K ≦ T ≦ 3500 K in a shock tube. Driving gas was Helium, shock wave carrier gas and collision partner was Argon. The free iron atoms were produced by the unimolecular decomposition of ironpentacarbonyl in the front of the incident shock wave.The initially produced iron condensate evaporates completely in the reflected shock wave to form free atoms. They are present behind the reflected shock wave in the form of a thermodynamically well defined undersaturated vapour. Thermodynamic quantities of the vapour do not change during the observation time. The line-broadening cross section σL(T) was measured by the method of integral atomic line absorption spectroscopy on the FeI-resonance line at 3859.91 Å to (10.05 ± 1.40) x 10-15 cm2 . Temperature variations in σL are smaller than experimental errors.

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