Study Of Shock Wave Propagation Research Articles

Numerical simulation of the influence of confined multi-point ignited H2–O2 mixture on the propagation of shock waves towards a deformable plate

The study of shock wave propagation in a detonation chamber is of great importance as a part of the plate forming process. Investigations related to the effects of premixed gas detonation on the deflection of a plate require in-depth examination. An Eulerian-Lagrangian numerical simulation is conducted using the space-time conservation element and solution element method of LS-DYNA software to study the effect of confined multi-point ignited gaseous mixture on the dynamic response of thin plates clamped at the end of a combustion chamber. The FSI couples a Lagrangian finite element solver with a Eulerian fluid solver in a 2D space with detailed chemistry of H2–O2 mixture. The solution contains the detonation wave propagation through the combustion chamber and its interaction with the plate. The influence of variation in the multi-point ignition locations and combustion chamber dimensions on the pressure history and plate deflection is studied. To verify the model, a comparison with the experimental study is carried out using an adjustable model representative of the real experiment. The verified model is used to link the evolution of plate shape with the arrival time and intensity of shock waves within the chamber. It is found that a longer distance between the ignition point and the plate intensifies the ultimate deflection of the plate. In addition, a fairly large combustion area employed in a direction rather than transverse to the plate surface is unable to influence the ultimate deformation of the plate.

Experimental study of shock wave propagation and its influence on the spontaneous ignition during high-pressure hydrogen release through a tube

An experimental study of shock wave propagation and its influence on the spontaneous ignition during high-pressure hydrogen release through a tube are measured by pressure transducers and light sensors. Results show that the pressure behind a shock wave first increases, and subsequently remains near constant value with an increase of the propagation distance. That is, a certain propagation distance is required to form a stable shock wave in the tube. In the front of the tube, the minimum value of pressure behind the shock wave (Pshock) required for spontaneous ignition decreases with the increase in axial distance to the diaphragm. However, the minimum Pshock remains nearly a constant value in the rear part of the tube. Moreover, the critical values of shock Mach number (MS) for spontaneous ignition decrease with the increase in tube length. And the ignition delay time decreases with the increase of the MS. As the ignition kernel grows in size to a flame, it propagates downstream along the tube with velocity greater than the theoretical flow velocity of the hydrogen-air contact surface. The flame propagation velocity relative to tube wall increases with MS. When the self-sustained flame exits from the tube, a rapid non-premixed turbulent combustion is observed in the chamber. The combustion-wave overpressure increases with the increase of the MS.

Experimental and numerical study of shock wave propagation in water generated by pulsed arc electrohydraulic discharges

The objective of this study is to simulate the propagation of the shock wave in water due to an explosion. The study is part of a global research program on the development of an alternative stimulation technique to conventional hydraulic fracturing in tight gas reservoirs aimed at inducing a distributed state of microcracking of rocks instead of localized fracture. We consider the possibility of increasing the permeability of rocks with dynamic blasts. The blast is a shock wave generated in water by pulsed arc electrohydraulic discharges. The amplitude of these shock waves is prescribed by the electrohydraulic discharges which generate high pressures of several kilobars within microseconds. A simplified method has been used to simulate the injected electrical energy as augmentation of enthalpy in water locally. The finite element code EUROPLEXUS is used to perform fluid fast dynamic computation. The predicted pressure is consistent with the experimental results. In addition, shock wave propagation characteristics predicted with simulation can be valuable reference for design of underwater structural elements and engineering of underwater explosion.

A lattice Boltzmann method for shock wave propagation in solids

AbstractThis paper proposes a new lattice Boltzmann (LB) method for the study of shock wave propagation in elastic solids. The method, which implements a flux‐corrected transport (FCT) algorithm, contains three stages: collision, streaming, and correction. In the collision stage, distribution functions are updated. In the streaming stage, the distribution functions are shifted between lattice points. Generally, a partial differential equation (PDE) is solved in the streaming stage, and finite element methods are employed to support the use of unstructured meshes in the LB method. The FCT algorithm is used in the correction stage to revise the distribution functions at lattice points, so fluctuations behind shock wave fronts can be eliminated efficiently. In this method, schemes for shock wave reflection at fixed and free boundaries are developed based on the bounce‐back technique. A similar technique is used to treat wave reflection and transmission at material interfaces of composites. Several one‐dimensional examples show that this LB‐FCT method can provide ideal depictions of shock wave propagation in structures, especially composite structures. Copyright © 2006 John Wiley & Sons, Ltd.

Study on Shock Wave Propagation under Saltwater Sealed in Aluminum Containers

The present paper reports the experimental and numerical study of shock wave propagation under saltwater sealed in aluminum containers. This study is the fundamental research on shock sterilization for development of ship's ballast water treatment technique. In the experiment we carried out the impact experiment with a gas gun to generate strong shock waves in saltwater. We confirmed that no leakage of saltwater from the aluminum container was obtained after shock events. The shock pressure fluctuations were measured with piezofilm gauges. Several hundred MPa pressure behind the first shock wave under the saltwater was obtained by the experiments. The FEM simulation, using the Johnson-Cook model for aluminum material and the Tait equation for salt-water, was carried out in order to predict the shock phenomena in both aluminum and saltwater. The computational results showed the states of stress and pressure in the container and indicated good agreements with the experimental results on the first shock pressure profiles at the impact velocities less than 200 m/s qualitatively and quantitatively.

An FE-FCT method with implicit functions for the study of shock wave propagation in solids

A finite element flux-corrected transport (FE-FCT) method is proposed for the study of shock wave propagation in solids. The FCT algorithm contains two stages: transport and antidiffusion. The total Lagrangian finite element method is used here and the FCT algorithm is only applied to correct the nodal velocities along the lines of the structured mesh. An implicit function is implemented into the finite element method so that the objective with arbitrary boundaries can be modeled with structured mesh. Both one-dimensional and two-dimensional examples show that the FE-FCT method can efficiently eliminate the oscillations behind the shock wave fronts.

409 高粘性媒体中の衝撃波伝播に関する基礎研究

409 高粘性媒体中の衝撃波伝播に関する基礎研究

The Effect of Material Heterogeneity on the Shock Response of Layered Systems in Plate Impact Tests

In the study of shock wave propagation in solids, scattering, dispersion, and attenuation play a critical role in determining the thermomechanical response of the media. These phenomena can be attributed to a number of nonlinearities arising from the wave characteristics, loading conditions, material heterogeneity (measured at various spatial scales ranging from nanometers to a few millimeters). The nonlinear effects in general can be ascribed to impedance (and geometric) mismatch present at various length scales as often encountered in composite material systems, apart from material nonlinearities arising from inelastic effects, void nucleation and growth, cracking, and delamination. However, in nearly brittle material systems, elastic effects dominate and is the only effect considered here. Uniaxial strain experiments on the S-2 glass/polymer composite system display markedly different behavior than that observed in monolithic metallic systems [6] and this motivated the present work. Stress profiles measured at various locations along the direction of wave propagation in the plate impact experiments showed that the shock wave rise time increased with propagation in addition to the reduction of peak stress. In this work, we specifically address the issue of shock wave rise time in a simplified multi-layered system. A careful analysis of wave propagation in heterogeneous medium is performed by considering the elastic/acoustic properties of individual lamina in a layered system. An analytical model has been developed to describe the scattering process (reflection/transmission) at various layer interfaces of multilayer composite system. FEM results are then used to compare with the analytical predictions. These results show that the rise time can be a consequence of multiple internal reflections and transmissions occurring at the heterogeneous interfaces, it is further shown that the rise time depends on the magnitude of impedance mismatch and the number of layers.

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

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.

An experimental and theoretical study of shock-wave propagation through reactive gases under conditions causing a transformation of the flow structure

Experimental observations of the transformation of the structure of shock waves entering the discharge gap of either a transverse or decaying glow discharge are presented. It is found that the total impulse of the shock wave pressure remains constant. A variation in the speed of sound, that is, the shock wave velocity, at which total dispersion of the wave occurs is found to be nonmonotonous across the discharge gap. The times over which the wave structure keeps changing after switching off the discharge have been more accurately determined. On the basis of the obtained experimental data and earlier results, a conclusion on the mechanism of this effect has been drawn. This mechanism is related to the dispersion of disturbances making up the wave structure in a relaxing medium (such as the glow discharge plasma). On the basis of a theory of this kind of dispersion, using the experimental data, and comparing energetic and temporal characteristics of the internal states of the plasma under study and the mode of sound disturbances (which according to the experiment, are responsible for the effect), we have succeeded in determining the O2(a1Δg) state whose relaxation brings about this effect.

X-ray diagnostic applied to the study of shock wave propagation in foams

A new radiographic technique has been studied in order to analyze the continuous evolution of shock wave propagation in low density foams. The technique is based on a Bragg–Fresnel multilayer lens. Preliminary static results, obtained by imaging a grid of suitable size, are presented.

COMPUTATION OF NON-STATIONARY SHOCK-WAVE/CYLINDER INTERACTION USING ADAPTIVE-GRID METHODS

A numerical study of shock wave propagation over a cylinder is presented. Hybrid, structured-unstructured adaptive grids are employed for the numerical solution of the Euler and Navier-Stokes equations. A second-order Godunov-type scheme is employed for the discretization of the inviscid fluxes, while central differences are used for the viscous terms. The time integration is obtained by a second-order prediction-corrector scheme. Simulation of the unsteady gasdynamic phenomena around the cylinder is obtained at different incident-shock Mach numbers. The shock-wave diffraction over the cylinder is investigated by means of various contour plots, as well as pressure and skin friction distributions. The calculations reveal that the Euler solutions are very close to the Navier-Stokes ones in the first half of the cylinder, but large differences between the two solutions exist in the second half of the cylinder and the wake of the flow field, where strong viscous-inviscid interaction occurs.

Peessure intensification on the front of a shock wave propagating in a heterogeneous system

An increase in pressure in the wave front as compared to the pulse initiating the wave has been observed experimentally in a study of shock-wave propagation in aqueous suspensions of bentonite [1]. In suspensions in which the solid phase is in the form of colloidal size particles δ=10−7−10−8 m of the mineral montmorillonite with mass content c=6%, with multishock loading an intensification of this effect from experiment to experiment was observed [2]. In order to study the principles involved in this anomalous “intensification” of pressure on the shock wave front, as well as to clarify the effect of the nature of the material in the dispersed phase, experiments were performed with particles of another broad class of clay-like minerals — kaolinite.

Numerical simulation of magnetohydrodynamic shock propagation in the corona

Recent developments in the field of numerical simulation models for the study of shock wave propagation in the corona are presented. These models are based on gasdynamic (GD) and ideal (that is, dissipationless, except at shocks) magnetohydrodynamic (MHD) theories. The characteristics and physical interpretations of the results derived from these models are discussed in some detail.

Optical inhomogeneities in a Lamberton-and-Pearson-type CO2laser

A simple optical technique for the detection of shock waves in a pulsed discharge is described. The technique uses an apertured photomultiplier and He-Ne probe laser to obtain data on the passage of a shock front across the pulsed discharge. This method has been applied to a study of shock wave propagation in a TEA CO2 laser discharge.

Flash Radiographic Study of Shock Wave Propagation in Laminated Composites

The flash radiographic method has been used to study the propagation of plane shock waves in laminated composites consisting of alternate layers of PMMA and aluminium. Experiments were arranged so that the shock waves could propagate in the direction parallel to the laminations. The shock front in each PMMA plate was observed to be slightly curved because of the impedance mismatch between constituents. An abrupt change in the area ratio of constituents was also observed at the section of constituents where the shock front was passing by. The average Hugoniot data obtained for laminated composites have been compared with previous theoretical models.

Dislocation mechanisms for stress relaxation in shocked LiF

A study of shock wave propagation along the 〈100〉 direction in LiF single crystals is presented. Plate impact experiments were conducted to produce elastic impact stresses of approximately 29 kbar. Stress time profiles at the impact surface and rear surface for thicknesses up to 3.2 mm were observed. Experiments were done for two impurity concentrations and three different heat treatments. Material characterization to supplement the shock data was provided by quasistatic yield stress measurements, dielectric relaxation data, initial dislocation density counts, and spectrographic analysis. Elastic wave attenuation is strongly influenced by both Mg++ impurities and heat treatments. Impurity clustering generally reduces the rate of precursor decay. The plastic strain rate at the elastic shock front was computed from the data by a near−exact method which incorporates material nonlinearities. Beyond the first 1 or 2 mm of propagation, significant contributions to stress decay arise from overtaking by relief waves. Application of dislocation theory reveals dislocation densities to be approximately 3 orders of magnitude larger than grown−in dislocations, at least in the region of rapid stress decay. Present analysis contradicts the idea of regenerative multiplication of dislocations causing this large increase in density. A model for heterogeneous nucleation of dislocation based on an energy criterion is proposed which appears to be well suited for explaining large increases in dislocation densities. The present data suggest an applied shear stress of 3−5 kbar as the lower bound at which dislocations can nucleate at heterogeneities present in our crystals. Better material characterization concerning impurity clusters is needed to consider the quantitative aspects of rate and magnitude of heterogeneous nucleation. The mechanism for stress decay in the very soft LiF crystals is still not well understood.

Study of shockwave propagation in a metal bar by high-speed interferometry

The work described in this paper is aimed at establishing the profile of the transient displacement of a point on the side of a long metal bar when a compression wave travels along it. The part of the bar to be examined is polished optically flat and is used as one reflector in a conventional two-beam interferometer. The passage of the wave distorts the polished area. The resulting transient fringe pattern, representing the distortion in the out-of-plane direction is recorded by high-speed streak photography. From the records obtained it is easy to derive high resolution graphs of displacement against time. In many cases satisfactory results can be obtained using a small mirror attached to the bar with adhesive, so avoiding the troublesome process of optically polishing part of the surface.