Explosive Wave Research Articles

Wave Dissipation Performance of Granular Media Based on Three-Dimensional Meso-Model

In this article, based on the real shape of gravel particles, a random polyhedron model is established, and a three-dimensional (3D) finite element (FE) analysis method is proposed to study the wave dissipation of broken gravel. In this article, the generation algorithm of 3D gravel with random size and shape is proposed, and the 3D meso-model of gravel particles is established. The numerical simulation of air explosion of explosive in free field is carried out by using LS-DYNA software, and the sensitivity of grid size was verified. Finally, it is concluded that the meshing calculation result of 0.01m element is more reliable. In order to verify the effectiveness of the analysis method, the numerical results are compared with the limited experimental data, and a good agreement is obtained, which shows that the 3D mesoscopic model and the numerical analysis method of gravel particle system can reliably predict the propagation of shock wave in gravel. Then, the wave dissipation performance of gravel layer under three working conditions of no water, partial water and all water is explored, and the dynamic response, energy analysis and meso-deformation of gravel particles are studied by numerical simulation. It is concluded that the gravel particle system significantly weakens the shock wave, and the peak pressure attenuates exponentially in the velocity direction, and the existence of water will affect the attenuation ability of the explosion wave.

Numerical Modelling of Gas Explosion Overpressure Mitigation Effects

The main aims of this study are to assess numerically the mitigation effects caused by the solid wall installed at the fueling station in order to protect personnel from the consequences of the emergent gas explosion, evaluate the optimal location of the wall and choose the appropriate material the wall have to be made of in order not to be destructed. A three-dimensional mathematical model of an explosion of hydrogen-air cloud is used. A computer technology how to define the personnel damage probability fields on the basis of probit analysis of the explosion wave is developed. The mathematical model takes into account the complex terrain and three-dimensional non-stationary nature of the shock wave propagation process. The model allows obtaining time-spatial distribution of damaging factors (overpressure in the shock wave front and the compression phase impulse) required to determine the three-dimensional non-stationary damage probability fields based on probit analysis. The developed computer technology allows to carry out an automated analysis of the safety situation at the fueling station and to conduct a comparative analysis of the effectiveness of different types of material the protective facilities made of.

Proliferation of soliton, explosive, shocklike, and periodic ion-acoustic waves in Titan's ionosphere

We report on many electrostatic nonlinear structures, namely, soliton, explosive, shocklike, and periodic waves, which may exist due to the dynamics of different ion species in Titan's ionosphere. Using the latest available observations of Titan at an altitude of ≈ 1300 km, the main ion components are HCNH+, C2H5+, and C3H5+. The dynamics of these waves are described by the Korteweg–de Vries (KdV) equation. Using the G′/G–expansion method, we obtain a class of solutions that elucidate these nonlinear structures. As the wave amplitude increases, both the width and velocity of the wave deviate from the prediction of the KdV equation. To describe the waves of larger amplitude, the higher-order dispersion has to be taken into account. The G′/G–expansion method is used, for the first time, to solve the KdV equation with higher-order dispersion. We compare between both KdV and higher-order dispersive KdV solutions, i.e., soliton, explosive, shocklike, and periodic waves.

RESEARCH ON ELECTROMAGNETIC RADIATION DURING THE EXPLOSION PROGRESS OF COMPOSITION B EXPLOSIVES

The electromagnetic radiation interference, which can be obviously observed during the explosives process, has attracted attention in many fields. However, the corresponding generation mechanism and theoretical model are still immature, experiments are still the key approach to study this phenomenon. This paper designs experiments to collect the electromagnetic radiation signals, generated by different charges of composition B explosives (Comp B), and uses the wavelet transform method to obtain these signals time-frequency characteristics, namely the main spectrum distribution is in the range of 0$\sim$50 kHz. Furthermore, the self-developed EXPOSION-3D software is used to simulate the experimental conditions to obtain the characteristics of the flow field during the explosion. By comparing the experimental results with the numerical simulations, series of conclusions are given in the following. The first pulse signal is the electromagnetic pulse directly generated by the high-temperature and high-pressure plasma generated by the detonation of Comp B; the second pulse signal is an electromagnetic pulse generated by the plasma formed at the air shock wave front which is caught up by the reflected shock wave from the ground; the third pulse signal is an invalid signal caused by the shock wave hitting the measurement coils. The amplitude of the first electromagnetic pulse has a linear relationship with the 1/3 power of the charge, and its arrival time is not sensitive to the charge of explosive. The time of the second electromagnetic pulse is in an exponential relationship with the charge of explosive. Overall, this paper put forward the characteristics of the explosion wave flow field when the shock wave reflection forms the electromagnetic wave signal, which provides verification data for the subsequent theoretical research.

Management of primary blast lung injury: a comparison of airway pressure release versus low tidal volume ventilation

BackgroundPrimary blast lung injury (PBLI) presents as a syndrome of respiratory distress and haemoptysis resulting from explosive shock wave exposure and is a frequent cause of mortality and morbidity in both military conflicts and terrorist attacks. The optimal mode of mechanical ventilation for managing PBLI is not currently known, and clinical trials in humans are impossible due to the sporadic and violent nature of the disease.MethodsA high-fidelity multi-organ computational simulator of PBLI pathophysiology was configured to replicate data from 14 PBLI casualties from the conflict in Afghanistan. Adaptive and responsive ventilatory protocols implementing low tidal volume (LTV) ventilation and airway pressure release ventilation (APRV) were applied to each simulated patient for 24 h, allowing direct quantitative comparison of their effects on gas exchange, ventilatory parameters, haemodynamics, extravascular lung water and indices of ventilator-induced lung injury.ResultsThe simulated patients responded well to both ventilation strategies. Post 24-h investigation period, the APRV arm had similar PF ratios (137 mmHg vs 157 mmHg), lower sub-injury threshold levels of mechanical power (11.9 J/min vs 20.7 J/min) and lower levels of extravascular lung water (501 ml vs 600 ml) compared to conventional LTV. Driving pressure was higher in the APRV group (11.9 cmH2O vs 8.6 cmH2O), but still significantly less than levels associated with increased mortality.ConclusionsAppropriate use of APRV may offer casualties with PBLI important mortality-related benefits and should be considered for management of this challenging patient group.

A three-dimensional simulation of the effects of obstacle blockage ratio on the explosion wave in a tunnel

In this paper, a three-dimensional simulation has been performed to investigate the potential consequences of flammable vapor explosion in a tunnel with an obstacle, the obstacle with different area blockage ratios (10, 20, 30 and 40%). The blast wave shape, increase in the maximum explosion overpressure, and the arrival time of peak pressure in the vicinity of the obstacle with different blockage ratios have been characterized. The simulation results show that the configuration of the blast wave was remarkably compressed due to the effects of obstacle and the deformation process which can be divided into four stages. The influence of blockage ratio on the maximum overpressure and the arrival time of peak pressure were mainly reflected in the back of the obstacle 1 m from the ground, and the maximum overpressure for this location decreases as the blockage ratio increases. Meanwhile, the maximum overpressure of 10% blockage ratio is 57% higher than that of 40% blockage ratio for the location of the back of obstacle. The arrival time of peak pressures for the location of the back of obstacle is delayed as the blockage ratio increases. The maximum overpressure under the tunnel ceiling showed an opposite trend between the location of the front of the obstacle and the location behind the obstacle. In the front of the obstacle, the maximum overpressure under the tunnel ceiling increases as the blockage ratio increases; however, it decreases as the blockage ratio increases in the back of the obstacle. What’s more, the comparison of this paper’s data and the results from available are published. It was found that the simulation results in this article are consistent with the experimental results of studies.

Experimental Study and Theoretical Verification of Explosion-Proof Performance of Insulated Glass

Building glass fragment in a blast-related environment is the main cause of casualties. In order to analyze the explosion-proof performance of insulated glass quantitatively in conventional buildings, the explosion experiment under different shock wave loads was carried out on the insulated glass, the pressure sensor was used to collect the overpressure value of the explosion shock wave, and the high-speed camera was used to record the breaking process of glass. The broken state of the insulated glass and the critical overpressure value of the broken state under different working conditions were obtained. And the theoretical calculation method based on the equivalent static load was used to verify the critical overpressure value of the insulated glass. The research showed that the fragments scattered toward the center of the explosion source when the layer of the insulated glass face to the explosion wave front was broken, and the fragments mainly scattered in the direction of the shock wave propagation when it was completely broken. The theoretical calculation method based on the equivalent static load could be used to evaluate the explosion-proof performance of the insulated glass.

Evolution of stress field in cylindrical blasting with bottom initiation

The dynamic caustic method and numerical simulation method were used to study explosive stress field of cylindrical blasting with bottom initiation. The explosive stress distribution of cylindrical blast holes with bottom initiation was not uniform, and can be divided into side areas with stronger stress and end areas with weaker stress with notable end effects. In the side areas, the explosive stress field at the initiating end increased, and the stress was high at the initial stage after initiation. However, the stress field at the non-initiating end was the strongest with the explosive detonation wave propagating from initiating end to non- initiating end. Differences in the principal stress difference near the blast hole were significant. The explosive stress field in the initiating end was weaker than that in the non-initiating end. Caustic spots increased and maximum principal stress directions is consistent with crack propagation direction when cracks propagated near circular holes. According to the simulation results, the Mises stress wave has a “conical” distribution. The Mises stress attenuation coefficient in the vertical direction, the axial direction, and the oblique direction increased at initiating end. The Mises stress attenuation coefficient in vertical direction, oblique direction, the axial direction increased at non-initiating end.

Pressure Wave Caused by Trinitrotoluene (TNT) Underwater Explosion—Short Review

The development of computational techniques and computer hardware has an impact the analysis of short-term (fast-changing) processes, such as the impact of a non-contact underwater explosion pressure waves. A theory of underwater explosions, gas bubble formation and pressure waves are presented. The course of the pressure wave in time, and its propagation in the acoustic medium are presented. The study presents empirical descriptions of non-contact pressure explosion waves. We propose to use them in simulations of ship hull strength and other objects immersed in liquids that are exposed to the effects of non-contact trinitrotoluene (TNT)-charge explosions. Pressure distributions and their time courses given by authors such as R.H. Cole, J.S. Nawagin, W. Stiepanow, T.E. Farley and H.G. Snay, T.L. Geers and K.S. Hunter are compared. A method of pressure wave modeling using acoustic media implemented in Computer Aided Engineering (CAE) programs is presented. The results of the values and the time course of the pressure acting on the underwater object are given. The influence of FEM (Finite Element Method) mesh density on the obtained results is examined and presented. The aim of the article is to expand our knowledge of underwater explosions, compare mathematical descriptions of the pressure waves developed by different authors and show the differences between them. In addition, we present the distinction between contact and non-contact explosions and analyze how changes in the mesh density of acoustic elements affects the reflection of the incident wave caused by an underwater explosion.

Research on piezoelectric pressure sensor for shock wave load measurement

The paper presents piezoelectric pressure sensor to measure the dynamic pressure of explosive shock wave in real time. Crystal group structural layout with acceleration compensation is designed by adding mass blocks. The static and dynamic model of the sensor is established to calculate the sensitivity and natural frequency. The influence of structural parameters of the sensor on its static and dynamic characteristics is analyzed. The mapping relationship between input and output of the sensor under different pressure loads is obtained by simulation. Prototype of the sensor under shock wave load is fabricated. Static and dynamic calibration platforms are built to complete calibration experiments. The experimental results show that the sensor can meet the measurement requirements of high frequency dynamic load signals.

Study on Pressure Characteristics and Its Evolution Law at the Ellipsoidal End Cover Pole of Cylindrical Explosion Containment Vessels

To explore the postposition of the maximum pressure at the pole of the ellipsoidal end cover of cylindrical explosion containment vessels and to reveal the mechanism of the load evolution, the experimental method was used to measure the pressure curve at the pole under different charges, and the numerical simulation method was used to analyze the evolution law of the explosion flow field within the end cover. The results show that the end cover pole was subjected to three types of pressure: the primary explosion wave, the secondary shock wave and the convergence wave. In addition, the pressure peaks increased in sequence. The evolution of the flow field in the end cover was affected by the amount of charge and the aspect ratio of the vessel. When the scaled distance due to a small charge increased, or when the aspect ratio of the vessel was reduced, the time interval between the convergence wave and the secondary shock wave at the end cover pole decreased gradually. When the scaled distance increased to 4.05 m·kg−1/3, the convergence wave at the pole superimposed on the secondary shock wave. As the aspect ratio of the vessel ranged from 1.75 to 2.50, the time interval between the two peaks was about 150 μs. However, if the aspect ratio was less than 1.40, the convergence wave and the secondary shock wave were fused through complex interaction.

Periventricular White Matter Alterations From Explosive Blast in a Large Animal Model: Mild Traumatic Brain Injury or "Subconcussive" Injury?

The neuropathology of mild traumatic brain injury in humans resulting from exposure to explosive blast is poorly understood as this condition is rarely fatal. A large animal model may better reflect the injury patterns in humans. We investigated the effect of explosive blasts on the constrained head minimizing the effects of whole head motion. Anesthetized Yucatan minipigs, with body and head restrained, were placed in a 3-walled test structure and exposed to 1, 2, or 3 explosive blast shock waves of the same intensity. Axonal injury was studied 3 weeks to 8 months postblast using β-amyloid precursor protein immunohistochemistry. Injury was confined to the periventricular white matter as early as 3-5 weeks after exposure to a single blast. The pattern was also present at 8 months postblast. Animals exposed to 2 and 3 blasts had more axonal injury than those exposed to a single blast. Although such increases in axonal injury may relate to the longer postblast survival time, it may also be due to the increased number of blast exposures. It is possible that the injury observed is due to a condition akin to mild traumatic brain injury or subconcussive injury in humans, and that periventricular injury may have neuropsychiatric implications.

Internal explosion load distribution and strain response of ellipsoidal end cover of explosion containment vessel

As a kind of limitation device of explosive products and shock wave, explosion containment vessel is widely used in military and civil fields. Due to its own structural characteristics, Mach wave convergence and collision will occur near the pole of the end cover of the cylindrical explosion containment vessel, resulting in a great pressure jump and seriously affecting the strain response characteristics of the end cover. In this paper, by means of experiment and numerical simulation, the distribution of flow field inside the end cover was explored, and it was found that the initial load of the end cover pole included the first incident wave of internal explosion, convergent re-incident wave of central section and the Mach wave convergence wave. By analyzing the strain spectrum, it is found that the different frequencies are excited by loads at different locations, so that the energy distribution under each frequency of strain is different, resulting in differences of strain. These results can provide reference for the design of explosion containment vessel.

Theoretical calculation for overpressure of air shock wave of explosion induced reaction of reactive material case

In order to study the power of the air shock wave produced by the reactive material driven by explosion, the reaction behavior of the reactive material driven by explosion was analyzed by AUTODYN@ software, and the reaction law of the reactive material was obtained. Considering the chemical energy released by the reactive material, the calculation model of shock wave initial parameters is improved. Combined with dimensional analysis, the theoretical calculation model for overpressure of air shock wave generated by the reactive material driven by explosion is studied. The results show that, under the driving of explosion, the casing made of the reactive material does not react completely. The velocity of air shock wave produced by the charge with reactive material casing is higher than that of the charge with inert material casing. The predicted value of the theoretical calculation model is in good agreement with the experimental results, and the established model can well describe the attenuation law of the air shock wave overpressure generated by the reactive material driven by the explosion.

Research on Influence Law of Explosion Load on New Subway Cross-structure

In order to reveal the influence law of explosion load when new subway under-crossing existing subway, the research with the method of combining theoretical calculation and numerical simulation was developed. With theoretical calculation method, the reasonable structural parameters and material parameters were chose, then the equivalent static load of under-crossing structure was obtained at the condition of explosion wave. By using the ANASYS/LS-DYNA software, the propagation law of explosion wave and the load change law of structure were simulated in four different models. Through comparison analysis, it showed the theoretical calculation method and numerical simulation method were rational, and the influence that existing subway on new under-crossing subway was only about the explosion wave propagation velocity except the explosion wave form and amplitude value, and the influence that new under-crossing subway on existing subway about explosion wave was very small. It provided a theoretical basis for design and construction for new under-crossing subway.

Drift wave in strong collisional dusty magnetoplasma

The study about the wave mechanism of magnetized dusty plasmas has important value to related experiment, industrial processing and exploring celestial space. The linear and nonlinear fluctuation characteristics of the nonuniform magnetized dust plasma system are researched in this paper. For the homogeneous external magnetic field and the nonuniform environment with density and temperature gradients, a two-dimensional nonlinear dynamic magnetoplasma equation is derived considering the strong impact between dust and neutral particles. The linear dispersion relation is obtained by the linearized method. There are both the damping wave causing by strong collision and the harmonic wave by particle drift. Employing the typical numerical parameters for analysis, the results display that the quantum parameter modifies the system lengths; the real wave frequency is proportion to the drift frequency; the imaginary wave frequency has complex relationship with the collision frequency between dust and neutrals, and the collision of particles causes the dissipation effects to the system. Besides, the analytical solutions of drift shock wave and explosive wave are solved by function change method. The variation about the electrostatic potential with the main physical parameters is discussed in detail. It is shown that the strength of the electrostatic shock wave and the width of the explosive wave increase with increasing the dust density and magnetic field intensity, decrease with increasing the collision frequency, change with the drift velocity. When the space-time phase is small, the electrostatic potential changes quickly; once big enough, the potential tends to be stable value and reaches stable state eventually. Finally, the stability of the system is discussed. It is found that the dusty charge, quantum parameter, drift velocity all appear in the disturbed solution. All these results in the paper show that the strong collision effect, quantum effect, particle drift and magnetic field all play important role to the generation, evolution and stability of drift waves.

Primary Blast Lung Injury: The UK Military Experience.

Primary blast lung injury occurs when an explosive shock wave passes through the thorax and transits through tissues of varying densities. It requires close proximity to an explosion and presents quick with respiratory distress in survivors. The Joint Theatre Trauma Registry and the Defence Statistics (Health) Database were interrogated for casualties injured as a result of an explosion during the conflict in Afghanistan. The case notes and imaging of casualties meeting the criteria for diagnosis were reviewed. Demographic and clinical data on casualties with primary blast lung injury were analyzed. 848 blast-exposed casualties survived to discharge from intensive care, and 238 blast-exposed casualties were killed in action. Following exclusions, 111 case notes and all postmortem reports were reviewed in detail. About, 25 casualties had isolated primary blast lung injury (2.9% of casualties surviving to discharge from intensive care) and 31 nonsurvivors (13% of nonsurvivors) had the disease documented at postmortem. Severe cases of primary blast lung injury required an estimated average of 4.5days of conventional mechanical ventilation. 8.1% of blast exposed casualties suffered primary blast lung injury. It was a less severe disease than other nontraumatic forms of acute lung injury and did not cause deaths once a casualty had reached a combat support hospital. It was well managed with a relatively brief period of conventional mechanical ventilation.

Spherical detonation waves of the Chapman–Jouguet combustion model

The study of spherically symmetric motion is important for the theory of explosion waves. In this paper, we construct rigorously self-similar detonation wave solutions to a Riemann initial–boundary value problem for the spherically symmetric Chapman–Jouguet combustion model. We give a detailed analysis to show that the problem does not have a strong detonation wave solution but has a Chapman–Jouguet detonation wave solution. We also obtain detailed structures of the Chapman–Jouguet detonation wave solution besides the existence.

Self-similar solutions of the radially symmetric relativistic Euler equations

The study of radially symmetric motion is important for the theory of explosion waves. We construct rigorously self-similar entropy solutions to Riemann initial-boundary value problems for the radially symmetric relativistic Euler equations. We use the assumption of self-similarity to reduce the relativistic Euler equations to a system of nonlinear ordinary differential equations, from which we obtain detailed structures of solutions besides their existence. For the ultra-relativistic Euler equations, we also obtain the uniqueness of the self-similar entropy solution to the Riemann initial-boundary value problems.

Analysis of seismic safety assessment procedures for joint development of coal deposits

The safety of mining and exploitation operations is an important factor that allows accident-free mining of mineral raw materials. To achieve this goal, the companies take various measures to reduce hazardous factors, which include blasting and distribution of seismic explosion waves as the phenomenon under consideration. The initial calculation for the reduction of hazardous factors is based on a specially designed procedure. Currently, there are no approved standard methods that could relate to impact of seismic explosion waves on the mounting of mine openings. Various researchers have developed procedures that have certain advantages and disadvantages. This paper presents the methods to assess seismic explosion impact during joint development of coal deposits, which are commonly applied in Russia. It shows the analysis of proposed methods and directions for further improvement of calculations of safe parameters of seismic explosion waves to mine openings.