Optical Diagnostics for Energetic Materials Research

2016 ◽  
Author(s):  
Michael J. Hargather ◽  
Joshua L. Smith ◽  
James Anderson ◽  
Kyle Winter
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Shock Waves ◽  
High Speed ◽  
Optical Diagnostics ◽  
Shock Wave Propagation ◽  
Field Scale ◽  
Schlieren Imaging ◽  
Image Field ◽  
Explosive Events

Optical diagnostics including schlieren, shadowgraphy, and background-oriented schlieren (BOS) are used to visualize shock waves and compressible flow phenomena present in energetic and explosive events. These techniques visualize refractive index variations to obtain a range of qualitative and quantitative information. A one-dimensional explosively-driven shock tube facility is used with schlieren imaging to measure shock wave propagation speeds from explosive-thermite mixtures. The schlieren imaging visualizes turbulent flow structures in the expanding product gas region. An imaging spectrometer is paired with the schlieren imaging to quantify the mixing of the explosive product gases with the ambient environment. Shadowgraphy is applied to image field-scale explosive tests. The shadowgraph images reveal shock waves, fragment motion and speed, and the motion of product gases. BOS is a modern technique for visualizing refractive fields via their distortion of a background pattern. Here the technique is applied to image field-scale explosive events using the ambient background of the test pad. The BOS images clearly show shock wave propagation and reflection from surfaces, which is not clearly visible in the raw high-speed digital images.

Experimental Contribution to the Modeling of Shock Propagation Induced by a Linear Pyrotechnical Source

2008 ◽  
Vol 51 (1) ◽  
pp. 122-145 ◽  
Author(s):  
Christelle Collet ◽  
Philippe Chabin ◽  
Henri Grzeskowiak
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
High Speed ◽  
Composite Plates ◽  
Shock Wave Propagation ◽  
Shock Propagation ◽  
Mechanical Responses ◽  
Space Agency ◽  
Out Of Plane ◽  
Space Launcher

In recent years, the phenomena occurring during shock wave propagation in spatial structures have been studied to characterize more accurately and to minimize the effects of pyrotechnical sources. As part of a program managed by the Centre National d'Etudes Spatiales (CNES, the French space agency), SNPE Matériaux Energétiques (SME) and MBDA France collaborated in a study to understand the mechanisms of shock wave propagation induced by the detonation of a linear pyrotechnical source. The focus of the study was on structures representative of space launcher structures such as those used for the Ariane 5 launcher. Various experiments were performed with metallic and composite plates, and two types of measurement devices (strain gauges and accelerometers) were investigated. Additional out-of-plane velocity and displacement measurements were provided by laser vibrometers, and displays of the separation of the plates were provided by a high-speed camera (up to 4800 feet/second). Signals treatment provided bending and compression strain describing plate mechanical responses. The apparatus used and the associated concerns that arose during the firings also are discussed.

Investigation of features of shock wave distribution in the rock massif at gas dynamic phenomena

2020 ◽  
pp. 234-243
Author(s):  
S.I. Skipochka ◽  
◽  
T.A. Palamarchuk ◽  
L.V. Prokhorets ◽  
V.P. Kurinnyi ◽  
...  
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Shock Waves ◽  
Shock Wave Propagation ◽  
Rock Massif ◽  
Mining Operations ◽  
Technological Factors ◽  
Gas Dynamic ◽  
Methane Mixture ◽  
Dynamic Phenomena

When studying risk factors in coal mines, it is necessary, in the first place, to consider factors and properties of the rock massif occurred with the deepening of mining operations in the coal mines, and determine one of the main types of danger: risk of geodynamic phenomena. The geodynamic phenomena occur and develop under the influence of natural and technological factors. Natural factors determine the rock massif proneness of ato geodynamic manifestations or, in other words, its potential danger due to these phenomena. Occurrence of this danger depends on technological factors. Among the dangerous factors of underground coal production to which primarily belong the geodynamic phenomena, the main ones are gas-dynamic phenomena, which are the most complex by their nature and dangerous by consequences due to high dynamic power and release of great amount of gas during a short period of time. Their consequences can be accidents due to sudden gassing and blockage of workings by coal and rock, explosions of methane and coal dust, destruction of the roadway supports, damage of machines and mechanisms, equipment and devices. As the gas-dynamic phenomena in the rocks massif are accompanied by occurrence of various processes differed by their nature, therefore, risks caused by them should be taken into account at mining operations. When considering the gas-dynamic phenomena attention should be paid to the shock wave propagation, as it is one of the gas dynamic processes. Therefore, purpose of this research was to study specific features of the shock wave propagation in the rock massif in order to prevent dangerous consequences. In this article, the authors consider the processes which occur in the rock massif prone to dangerous gas-dynamic phenomena at the shock wave propagation. The methods of rock mechanics, mechanics of continuous media, gas and thermodynamics were used in the research. Analytical researches of processes and numerical analysis of the received results were carried out. It is shown that a sharp increase of thermodynamic parameters under the action of gas-dynamic phenomena can lead to occurrence of the shock waves. It is further established that an explosive air-methane mixture can be formed in cracks, cavities and pores of the face area. At opening the cavities and pores, cases of shock waves formation in air-methane mixture leading to its detonation are possible. Under adverse conditions, this phenomenon can lead to a fire in the roadway.

Shock-wave induced instability in internal explosion dynamics

2005 ◽  
Vol 109 (1101) ◽  
pp. 537-556 ◽  
Author(s):  
A. Bagabir ◽  
D. Drikakis
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Shock Waves ◽  
Symmetry Breaking ◽  
Flow Instability ◽  
Shock Wave Propagation ◽  
Vortical Flow ◽  
Density Region ◽  
Riemann Solvers ◽  
Wave Induced

Abstract The paper presents an investigation of flow instabilities occurring in shock-wave propagation and interaction with the walls of an enclosure. The shock-wave propagation is studied in connection with perturbed and unperturbed cylindrical blasts, initially placed in the centre of the enclosure, as well as for three different blast intensities corresponding to Mach numbers Ms = 2, 5 and 10. The instability is manifested by a symmetry-breaking of the flow even for the case of an initially perfectly-symmetric blast. It is shown that the symmetry-breaking initiates around the centre of the enclosure as a result of the interaction of the shock waves reflected from the walls, with the low-density region in the centre of the explosion. The instability leads to fast attenuation of the shock waves, especially for smaller initial blast intensities. The computations reveal that the vortical flow structures arising from the multiple shock reflections and flow instability are Mach number dependent. The existence of perturbations of large amplitude in the initial condition strengthens the instability and has significant effects on the instantaneous wall pressure distributions. The computational investigation has been performed using high-resolution Riemann solvers for the gas dynamic equations.

Propagation of Weak Shock Waves in a Vibrational Nonequilibrium, Nonuniform Gas

1975 ◽  
Vol 42 (3) ◽  
pp. 564-568 ◽  
Author(s):  
D. C. Chou ◽  
S. Y. Maa
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Shock Waves ◽  
Vibrational Energy ◽  
Weak Shock ◽  
Present Theory ◽  
Shock Wave Propagation ◽  
Perturbation Scheme ◽  
Relaxation Rates ◽  
Vibrational Nonequilibrium

Problems concerned with the propagation of weak planar shock waves in a nonuniform, nonequilibrium gas is theoretically investigated. The medium under consideration is a diatomic thermally perfect gas with excited vibrational energy and is initially inhomogeneous with exponential density and temperature distributions. The systematic characteristic perturbation scheme is employed to render a first-order frozen shock expression. It is shown quantitatively that combined effects of nonequilibrium, nonlinearity, and stratification govern the nature of the shock wave propagation. The uniform gas limit of present theory agrees with previously known results of shock wave propagation in a general relaxing fluid. Numerical examples illustrate the variation of frozen shock strength and speed due to different magnitudes of relaxation rates and inhomogeneity. The interesting competition phenomenon between nonequilibrium effects and nonuniform effects on shock wave propagation is examined.

Numerical Study on Shock Wave Propagation with Obstacles during Methane Explosion

2010 ◽  
Vol 33 ◽  
pp. 114-118 ◽  
Author(s):  
Zhi Ming Qu
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Velocity Gradient ◽  
High Speed ◽  
Numerical Study ◽  
Shock Wave Propagation ◽  
Gradient Field ◽  
Shock Propagation ◽  
Mixture Flow ◽  
Methane Mixture

During shock wave propagation in the pipeline, the flow field of speed, pressure and temperature is evenly distributed. If there are obstacles, then the flow will be changed while the velocity gradient is formed near the obstacles. Passing through the obstacles, a high-speed gradient of the unburned methane mixture flow is established. While reaching the obstacle, the shock wave surface is rapidly stretched to increase the significant transmission speed. Propagating in the gradient field, the shock wave will be stretched and folded. The deformation of shock wave causes consumption of fuel and oxygen in greater unburned methane surface, which results in heat release rate increasing and faster shock propagation. In conclusion, shock wave causes larger advection speed in front of the unburned methane mixture, increasing flow velocity gradient further and leading to more intense shock wave propagation.

scholarly journals Experimental Study on Shock Wave Propagation of the Explosion in a Pipe with Holes by High-Speed Schlieren Method

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Gang Zhang
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
High Speed ◽  
Experimental System ◽  
Test System ◽  
Shock Wave Propagation ◽  
Oblique Shock Wave ◽  
Schlieren Method ◽  
Wave Fronts ◽  
Blast Energy

The shock wave propagation of the explosion in a pipe with holes was studied by a high-speed schlieren experimental system. In the experiments, schlieren images in the explosion were recorded by a high-speed camera from parallel and perpendicular orientations, respectively, and the pressure in the air was measured by an overpressure test system. In parallel orientation, it is observed that the steel pipe blocks the propagation of blast gases, but it allows the propagation of shock waves with a symmetrical shape. In perpendicular orientation, oblique shock wave fronts were observed, indicating the propagation of explosion detonation along the charge. Shock wave velocity in the hole direction is larger than that in the nonhole direction, indicating the function of holes in controlling blast energy, that is, leading blast energy to hole direction. Furthermore, the function of holes is verified by overpressure measurements in which peak overpressure in the hole direction is 0.87 KPa, 2.8 times larger than that in the nonhole direction. Finally, the variation of pressure around the explosion in a pipe with holes was analyzed by numerical simulation, qualitatively agreeing with high-speed schlieren experiments.

High Speed Photography For Studying The Shock Wave Propagation At High Mach Numbers Through A Reflection Nozzle

1979 ◽  
Author(s):  
S. G. Zaytsev ◽  
E. V. Lazareva ◽  
A. V. Mikhailova ◽  
V. L. Nikolaev-Kozlov ◽  
E. I. Chebotareva
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
High Speed ◽  
Shock Wave Propagation ◽  
High Speed Photography ◽  
Mach Numbers ◽  
High Mach

scholarly journals Study of laser-driven shock wave propagation in Plexiglas targets

1992 ◽  
Vol 10 (1) ◽  
pp. 201-211 ◽  
Author(s):  
L. J. Dhareshwar ◽  
P. A. Naik ◽  
T. C. Kaushik ◽  
H. C. Pant
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
High Speed ◽  
Second Harmonic ◽  
Optical Probe ◽  
Shock Wave Propagation ◽  
Hydrodynamic Simulation ◽  
One Dimensional ◽  
Laser Beam Irradiation ◽  
Shock Fronts

An experimental study of laser-driven shock wave propagation in a transparent material such as Plexiglas using a high-speed optical shadowgraphy technique is presented in this paper. A Nd:glass laser was used to produce laser intensity in the range 1012-1014 W/cm2 on the target. Optical shadowgrams of the propagating shock front were recorded with a second-harmonic (0.53-μm) optical probe beam. Shock pressures were measured at various laser intensities, and the scaling was found to agree with the theoretically predicted value. Shock pressure values have also been obtained from a one-dimensional Lagrangian hydrodynamic simulation, and they match well with experimental results. Shadowgrams of shock fronts produced by nonuniform spatial laser beam irradiation profiles have shown complete smoothing when targets with a thin coating of a material of high atomic number such as gold were used. Shock pressures in such coated targets are also found to be considerably higher compared with those in uncoated targets.

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