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.

Experimental and numerical study of the interaction between a planar shock wave and a square cavity

1996 ◽  
Vol 313 ◽  
pp. 105-130 ◽  
Author(s):  
O. Igra ◽  
J. Falcovitz ◽  
H. Reichenbach ◽  
W. Heilig
Keyword(s):  
Shock Wave ◽  
Physical Model ◽  
Numerical Study ◽  
Wave Pattern ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Square Cavity ◽  
Planar Shock ◽  
Shock Wave Interactions ◽  
Planar Shock Wave

The interaction of a planar shock wave with a square cavity is studied experimentally and numerically. It is shown that such a complex, time-dependent, process can be modelled in a relatively simple manner. The proposed physical model is the Euler equations which are solved numerically, using the second-order-accurate high-resolution GRP scheme, resulting in very good agreement with experimentally obtained findings. Specifically, the wave pattern is numerically simulated throughout the entire interaction process. Excellent agreement is found between the experimentally obtained shadowgraphs and numerical simulations of the various flow discontinuities inside and around the cavity at all times. As could be expected, it is confirmed that the highest pressure acts on the cavity wall which experiences a head-on collision with the incident shock wave while the lowest pressures are encountered on the wall along which the incident shock wave diffracts. The proposed physical model and the numerical simulation used in the present work can be employed in solving shock wave interactions with other complex boundaries.

Shock waves in microchannels

2013 ◽  
Vol 724 ◽  
pp. 259-283 ◽  
Author(s):  
G. Mirshekari ◽  
M. Brouillette ◽  
J. Giordano ◽  
C. Hébert ◽  
J.-D. Parisse ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Large Scale ◽  
Numerical Models ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Navier Stokes ◽  
Shock Attenuation ◽  
Pressure Time ◽  
Time Histories

AbstractA fully instrumented microscale shock tube, believed to be the smallest to date, has been fabricated and tested. This facility is used to study the transmission of a shock wave, produced in a large (37 mm) shock tube, into a 34 $\mathrm{\mu} \mathrm{m} $ hydraulic diameter and 2 mm long microchannel. Pressure microsensors of a novel design, with gigahertz bandwidth, are used to obtain pressure–time histories of the microchannel shock wave at five axial stations. In all cases the transmitted shock wave is found to be weaker than the incident shock wave, and is observed to decay both in pressure and velocity as it propagates down the microchannel. These results are compared with various analytical and numerical models, and the best agreement is obtained with a Navier–Stokes computational fluid dynamics computation, which assumes a no-slip isothermal wall boundary condition; good agreement is also obtained with a simple shock tube laminar boundary layer model. It is also found that the flow developing within the microchannel is highly dependent on conditions at the microchannel entrance, which control the mass flux entering into the device. Regardless of the micrometre dimensions of the present facility, shock wave propagation in a microchannel of that scale exhibits a behaviour similar to that observed in large-scale facilities operated at low pressures, and the shock attenuation can be explained in terms of accepted laminar boundary models.

Shock tube study of particles' motion behind a planar shock wave

2005 ◽  
Vol 16 (12) ◽  
pp. 2431-2436 ◽  
Author(s):  
Tateyuki Suzuki ◽  
Yoshitaka Sakamura ◽  
Ozer Igra ◽  
Takashi Adachi ◽  
Susumu Kobayashi ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Planar Shock ◽  
Planar Shock Wave ◽  
Tube Study

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.

scholarly journals Blast mitigation by perforated plates using an explosive driven shock tube: study of geometry effects and plate numbers

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
T. Schunck ◽  
D. Eckenfels
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Blast Wave ◽  
Perforated Plate ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Metallic Foam ◽  
Blast Mitigation ◽  
Geometric Means ◽  
Perforated Plates

AbstractThis work is set in the context of blast mitigation based on geometric means, namely perforated metallic plates or grids. When a shock wave passes through a perforated plate, the flow field is modified, and new shock waves are created, as well as regions of vortices and turbulence in which the energy of the wave can be dissipated. In this study, an explosive driven shock tube (EDST) was used to visualize the interaction of a blast wave with perforated plates or with a piece of cast metallic foam. Additionally, the overpressure and the impulse of the reflected blast wave on a wall located downstream were assessed. The use of an EDST allowed the evaluation of the mitigation capacity under a high dynamic loading. Several combinations of perforated plates were tested, varying the geometry and the number of plates, as well as switching between two different spacings. When the shock wave collided with a plate, we observed that part of the incident shock wave was reflected by the plate, while the remaining wave was transmitted through it. Downstream of the plate, both the overpressure and the impulse were reduced, this effect being more prominent as the porosity of the plates decreased. When two plates were placed as obstacles, this phenomenon of reflection/transmission was repeated twice consecutively, further reducing the downstream reflected overpressure and impulse. An array of three plates or a piece of metallic foam were even more effective in mitigating the blast wave. Varying the distance between two or three plates had no effect on blast mitigation.

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.

Sign in / Sign up

Export Citation Format

Share Document