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Research Papers: Flows in Complex Systems

Experimental and Numerical Investigation of Shock Wave Attenuation by Dynamic Barriers

[+] Author and Article Information
Shahar Berger

Department of Mechanical Engineering,
Faculty of Engineering Studies,
Ben-Gurion University of the Negev,
Beer Sheva 84105, Israel
e-mail: bergersh@bgu.ac.il

Gabi Ben-Dor

Professor
Pearlstone Center for Aeronautical
Engineering Studies,
Protective Technologies R&D Center,
Faculty of Engineering Studies,
Ben-Gurion University of the Negev,
Beer Sheva 84105, Israel
e-mail: bendorg@bgu.ac.il

Oren Sadot

Professor
Pearlstone Center for Aeronautical
Engineering Studies,
Protective Technologies R&D Center,
Faculty of Engineering Studies,
Ben-Gurion University of the Negev,
Beer Sheva 84105, Israel
e-mail: sorens@bgu.ac.il

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 12, 2015; final manuscript received August 13, 2015; published online October 1, 2015. Assoc. Editor: Oleg Schilling.

J. Fluids Eng 138(3), 031103 (Oct 01, 2015) (14 pages) Paper No: FE-15-1100; doi: 10.1115/1.4031375 History: Received February 12, 2015; Revised August 13, 2015

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.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Schematic illustration of the experimental setup: (a) the shock tube, the laser beam path, the mirrors, and the high-speed camera arrangement and (b) the barrier and the pressure transducers arrangement inside the test section

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Fig. 2

The interaction of a Mach = 1.2 shock wave with a 1-mm thick barrier (time presented 0 ≤ t ≤ 0.15 ms)

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Fig. 3

The interaction of a Mach = 1.2 shock wave with a 1-mm thick barrier (time presented 0.2 ms ≤ t ≤ 0.35 ms)

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Fig. 4

The interaction of a Mach = 1.2 shock wave with a 1-mm thick barrier (time presented 0.6 ms ≤ t ≤ 2.6 ms)

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Fig. 5

Pressure history signals along the shock tube (C2) and the test section (C3 and C4)

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Fig. 6

Opening ratio of a dynamic barrier versus time for two barrier plate thicknesses

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Fig. 7

Pressure history signals along the shock tube (C2) and the test section (C3 and C4) (dashed lines—numerical calculation and solid lines—experimental results)

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Fig. 8

Comparison between the experiments and the simulations. Schlieren images of the interaction of a 1.5-mm thick barrier with a Mach = 1.2 shock wave (time presented 0.1 ms ≤ t ≤ 0.4 ms).

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Fig. 9

Comparison between experiment (plus marks) and simulation (solid line) of the dynamic barrier movement (opening ratio) versus time

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Fig. 10

Pressure history signals along the shock tube (C2) and the test section (C4) for 1.5-mm thick aluminum and steel barrier plates, Mach number 1.2 (solid line) and 1.4 (dashed line)

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Fig. 11

Opening ratio of a dynamic barrier versus time for 1.5-mm thick aluminum and steel barrier plates, Mach number 1.2 (solid line) and 1.4 (dashed line)

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Fig. 12

The simulation mesh and the pressure transducers arrangement inside the test section

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Fig. 13

Simulated density images of the interaction of a Mach = 1.4 shock with a 10-mm thick aluminum barrier (time presented − 17 ms ≤ t ≤ 1183 ms)

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Fig. 14

Pressure history signals along the shock tube test section (C2, C3, and C4), for metal rotating barrier

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Fig. 15

Simulated density images of the interaction of a Mach = 1.4 shock with a 10-mm thick rubber barrier (time presented − 17 ms ≤ t ≤ 1183 ms)

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Fig. 16

Pressure history signals along the shock tube test section (C2, C3, and C4), for restrained rubber barrier

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Fig. 17

Effective stress in MPa along the stressed barriers (density in kg/m3)

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