scholarly journals Shock focusing in a planar convergent geometry: experiment and simulation

2009 ◽  
Vol 641 ◽  
pp. 297-333 ◽  
Author(s):  
C. BOND ◽  
D. J. HILL ◽  
D. I. MEIRON ◽  
P. E. DIMOTAKIS
Keyword(s):  
Shock Wave ◽  
Shock Focusing ◽  
Multiple Reflections ◽  
Reflected Waves ◽  
Additional Tool ◽  
Planar Shock ◽  
Real Gas Effects ◽  
Shock Wave Focusing ◽  
Planar Shock Wave ◽  
Shock Mach Number

The behaviour of an initially planar shock wave propagating into a linearly convergent wedge is investigated experimentally and numerically. In the experiment, a 25° internal wedge is mounted asymmetrically in a pressure-driven shock tube. Shock waves with incident Mach numbers in the ranges of 1.4–1.6 and 2.4–2.6 are generated in nitrogen and carbon dioxide. During each run, the full pressure history is recorded at fourteen locations along the wedge faces and schlieren images are produced. Numerical simulations performed based on the compressible Euler equations are validated against the experiment. The simulations are then used as an additional tool in the investigation.The linearly convergent geometry strengthens the incoming shock repeatedly, as waves reflected from the wedge faces cross the interior of the wedge. This investigation shows that aspects of this structure persist through multiple reflections and influence the nature of the shock-wave focusing. The shock focusing resulting from the distributed reflected waves of the Mach 1.5 case is distinctly different from the stepwise focusing at the higher incoming shock Mach number. Further experiments using CO2 instead of N2 elucidate some relevant real-gas effects and suggest that the presence or absence of a weak leading shock on the distributed reflections is not a controlling factor for focusing.

Planar Shock Focusing Through Perfect Gas Lens: First Experimental Demonstration

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Laurent Biamino ◽  
Christian Mariani ◽  
Georges Jourdan ◽  
Lazhar Houas ◽  
Marc Vandenboomgaerde ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Shock Acceleration ◽  
Perfect Gas ◽  
Shock Focusing ◽  
Planar Case ◽  
Planar Shock ◽  
Planar Shock Wave

When a shock wave crosses an interface between two materials, this interface becomes unstable and the Richtmyer–Meshkov instability develops. Such instability has been extensively studied in the planar case, and numerous results were presented during the previous workshops. But the Richtmyer–Meshkov (Richtmyer, 1960, “Taylor Instability in Shock Acceleration of Compressible Fluids,” Commun. Pure Appl. Math., 13(2), pp. 297–319; Meshkov, 1969, “Interface of Two Gases Accelerated by a Shock Wave,” Fluid Dyn., 4(5), pp. 101–104) instability also occurs in a spherical case where the convergence effects must be taken into account. As far as we know, no conventional (straight section) shock tube facility has been used to experimentally study the Richtmyer–Meshkov instability in spherical geometry. The idea originally proposed by Dimotakis and Samtaney (2006, “Planar Shock Cylindrical Focusing by a Perfect-Gas Lens,” Phys. Fluid., 18(3), pp. 031705–031708) and later generalized by Vandenboomgaerde and Aymard (2011, “Analytical Theory for Planar Shock Focusing Through Perfect Gas Lens and Shock Tube Experiment Designs,” Phys. Fluid., 23(1), pp. 016101–016113) was to retain the flexibility of a conventional shock tube to convert a planar shock wave into a cylindrical one through a perfect gas lens. This can be done when a planar shock wave passes through a shaped interface between two gases. By coupling the shape with the impedance mismatch at the interface, it is possible to generate a circular transmitted shock wave. In order to experimentally check the feasibility of this approach, we have implemented the gas lens technique on a conventional shock tube with the help of a convergent test section, an elliptic stereolithographed grid, and a nitrocellulose membrane. First experimental sequences of schlieren images have been obtained for an incident shock wave Mach number equal to 1.15 and an air/SF6-shaped interface. Experimental results indicate that the shock that moves in the converging part has a circular shape. Moreover, pressure histories that were recorded during the experiments show pressure increase behind the accelerating converging shock wave.

scholarly journals Planar shock wave sliding over a water layer

2016 ◽  
Vol 57 (8) ◽  
Author(s):  
V. Rodriguez ◽  
G. Jourdan ◽  
A. Marty ◽  
A. Allou ◽  
J.-D. Parisse
Keyword(s):  
Shock Wave ◽  
Water Layer ◽  
Planar Shock ◽  
Planar Shock Wave

Flow of a planar shock wave around a thermal layer at a rigid wall

1991 ◽  
Vol 31 (3) ◽  
pp. 354-361
Author(s):  
B. I. Zaslavskii ◽  
S. Yu. Morozkin ◽  
A. A. Prokof'ev ◽  
V. R. Shlegel'
Keyword(s):  
Shock Wave ◽  
Rigid Wall ◽  
Planar Shock ◽  
Planar Shock Wave ◽  
Thermal Layer

Specifics of generating explosively formed projectiles of variable shape from metal liners

2019 ◽  
Author(s):  
P.V. Kruglov ◽  
V.I. Kolpakov ◽  
I.A. Bolotina
Keyword(s):  
Shock Wave ◽  
Aspect Ratio ◽  
Detonation Wave ◽  
Variable Shape ◽  
Internal Surfaces ◽  
Planar Shock ◽  
Wave Generator ◽  
Planar Shock Wave ◽  
Metal Liner ◽  
A Charge

We propose using charges generating explosively formed projectiles of variable shape to remotely demolish structurally unsound concrete or brick walls of buildings and other structures. The paper considers the charges required, their design and operation. The operation of such a charge involves the explosive material accelerating a metal liner, covering a distance of up to several hundred charge diameters. The metal liner deforms while moving and assumes a compact shape. We used variable thickness copper liners, the external and internal surfaces of which are formed by a combination of spherical surfaces. A planar shock wave generator featuring a variable detonation wave slope is considered as the initiation system for the charge. We present the results of numerically simulating our explosive charge operation in order to determine how charge parameters affect performance. We estimated charge performance via two projectile parameters: its shape and velocity. The study also evaluated the effect of the planar shock wave generator slope on the projectile shape. We obtained projectile velocity and aspect ratio as functions of the slope of the converging detonation wave. We determined that decreasing the slope of the converging detonation wave front leads to an increase in the aspect ratio and velocity of the explosively formed projectile.

Experimental and theoretical study of shock wave propagation through double-bend ducts

2001 ◽  
Vol 437 ◽  
pp. 255-282 ◽  
Author(s):  
O. IGRA ◽  
X. WU ◽  
J. FALCOVITZ ◽  
T. MEGURO ◽  
K. TAKAYAMA ◽  
...  
Keyword(s):  
Shock Wave ◽  
Wave Attenuation ◽  
Wave Pattern ◽  
Complex Flow ◽  
Shock Wave Attenuation ◽  
Planar Shock ◽  
Wave Patterns ◽  
Planar Shock Wave ◽  
Flow Evolution ◽  
Interferometric Study

The complex flow and wave pattern following an initially planar shock wave transmitted through a double-bend duct is studied experimentally and theoretically/numerically. Several different double-bend duct geometries are investigated in order to assess their effects on the accompanying flow and shock wave attenuation while passing through these ducts. The effect of the duct wall roughness on the shock wave attenuation is also studied. The main flow diagnostic used in the experimental part is either an interferometric study or alternating shadow–schlieren diagnostics. The photos obtained provide a detailed description of the flow evolution inside the ducts investigated. Pressure measurements were also taken in some of the experiments. In the theoretical/numerical part the conservation equations for an inviscid, perfect gas were solved numerically. It is shown that the proposed physical model (Euler equations), which is solved by using the second-order-accurate, high-resolution GRP (generalized Riemann problem) scheme, can simulate such a complex, time-dependent process very accurately. Specifically, all wave patterns are numerically simulated throughout the entire interaction process. Excellent agreement is found between the numerical simulation and the experimental results. The efficiency of a double-bend duct in providing a shock wave attenuation is clearly demonstrated.

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