Explosion Shock Wave Research Articles

Model for explosive shock waves in fluids with relaxation

Model for explosive shock waves in fluids with relaxation

Numerical assessment of hydrogen explosion consequences in a mine tunnel

The aim of the work is a numerical estimation of the conditional probability of damage to the mine personnel during an accidental explosion of a hydrogen-air mixture. The methodology for determining the parameters of the gas-dynamic process of the explosion of a hydrogen-air cloud in an open and closed space, taking into account chemical interaction and space clutter, is presented. A computational method based on a probit analysis for determining the damage probability fields of a person exposed to the explosion shock wave has been developed. To automate the computational process, the tabular dependence “probit-function-damage probability” is replaced by a piecewise cubic spline. Numerical studies of the influence of the drift working space clutter by an electric locomotive on the distribution of the overpressure of the gaseous medium and the conditional probability of the eardrums rupture and lethal damage to personnel in the accidental zone of the coal mine have been carried out. It was obtained that the closed nature of the working space and its blockage significantly changes the shape and size of the danger zone and requires consideration by an expert at the stage of deciding on the safety level at the mine. The scientific novelty of the method proposed in the work is in taking into account in the mathematical model of the movement of a multi-component chemically reacting gas mixture the effect of compressibility of flow, complex terrain (space clutter with equipment), three-dimensional nature of the gas-air mixture dispersion process. The model allows obtaining the space-time distributions of the shock-impulse load of the blast wave that is necessary for determining the non-stationary three-dimensional fields of the conditional probability of damage to the staff on the basis of probit analysis. The developed computational method allows analyzing and forecasting in time and space the conditional probability of damage of varying degrees of severity of personnel who are exposed to an explosive shock wave as an indicator of the safety level of a coal mine.

Meso-Complexity Computer Simulation Investigation on Antiexplosion Performance of Double-Layer Foam Aluminum under Pore Grading

Foam aluminum is an energy-absorbing material with excellent performance. The interlayer composed of multiple layers of foam aluminum and steel plate has good antiexplosion ability. In order to explore the antiexplosion performance of double-layer foam aluminum under different porosity rankings and to reveal its microscopic deformation law and failure mechanism, three kinds of aluminum foams with a porosity of 80%, 85%, and 90% were selected to form six different structures. Based on the Voronoi algorithm, a three-dimensional foam aluminum generation algorithm with random pore size and random wall thickness was written by using the Python language and Fortran language. The three-dimensional mesoscopic model of double-layer closed-cell aluminum foam sandwich panel is established by using LS-DYNA and ABAQUS software. The explosion process was simulated, and the flow field movement of explosion shock wave of aluminum foam under different porosity rankings was analyzed. Two groups of aluminum foam were randomly selected for the explosion test and compared for the strain and compression. The test results are consistent with the simulation results, which verifies the correctness of the three-dimensional meso-model. The results show that when the porosity of the upper layer of aluminum foam is greater than that of the lower layer of aluminum foam, the sandwich structure of double-layer aluminum foam has a large compression and the bottom plate has a small displacement; it is not that the greater the compression amount of aluminum foam is, the better the antiexplosion and wave absorption ability is. When the aluminum foam reaches the ultimate load-bearing capacity, the aluminum foam transfers the load due to compaction, resulting in stress enhancement phenomena. Through the analysis of the compression amount, floor deformation, wave dissipation capacity, and energy ratio of aluminum foam, it is concluded that the antiexplosion wave absorption effect of the sandwich structure of aluminum foam with 80%/85% group is the best; the changes of porosity and cell wall are important factors affecting the energy absorption capacity of aluminum foam.

Study on the failure mode of a sandwich composite structure under the combined actions of explosion shock wave and fragments

To improve the protective performance of structures in terms of explosive shock waves and fragment penetration, a foamed aluminum/UHMWPE fiber sandwich composite structure was designed. A “explosion+fragmentation” penetration experiment was used to study the failure mode of the structure and the failure mechanisms of materials, the effects of the core material combination and explosion distance were discussed, meanwhile, numerical simulation using LS-DYNA was adopted to simulate the timing and distribution law of the shock wave and fragments. The results show that the explosion distance is the main influencing factor for the timing, and the experimental and numerical results have a good consistency. When the structure was perforated completely by fragments, the front aluminum plate was damaged mainly by shear plugging, and the rear aluminum plate was broken largely by cracking and tearing. When the fragments arrived prior to the shock wave, the tearing damage to the rear aluminum plate was more obvious. The foamed aluminum absorbed the explosive energy through its own crushing deformation, and the fiber layer absorbed the kinetic energy of the fragments through its own tensile failure. Of the composite structures prepared herein, the composite structure consisting of foamed aluminum/foamed aluminum/UHMWPE fiber had the best protection performance.

Experimental study on hydrogen-air premixed gas explosion in confined space

ABSTRACT In order to explore the explosion characteristics of hydrogen-air premixed mixtures and to characterize the damaging effect of the explosion shock wave on the surrounding structures, a closed straight detonation pipeline is designed and applied to simulate a confined space in this study. The inner diameter of the designed pipeline is 6.4 m long and 125 mm wide. The results show that the maximum flame speed of the most combustible premixed gases usually occurs near the equivalent ratio of 1 (hydrogen volume concentration is 29.6%). However, because of the influence of Graham’s law in chemical reaction kinetics, the maximum flame speed of hydrogen/air premixed gas appears near the equivalent ratio of 1.5 (hydrogen volume concentration is 39.6%). At this concentration, the maximum flame propagation speed reaches 1810 m/s and the pressure peak reaches 1.53 MPa. The elbow structure has a significant effect on the explosion flame. The explosion pressure and flame propagation velocity drop sharply when the premixed gas enters the bend. The explosion pressure is reduced by 11.3% and the flame propagation velocity is reduced by 66.59%. However, the velocity of flame propagation increases by a maximum of 34.41%, and the explosion pressure increases by a maximum of 26.1% when the premixed gas passes the turning point of the elbow. The thin-wall strain response of the pipeline is in good agreement with the explosion pressure.

Optimal Design of Presplit Blasting Network of Deep Concave Open-Pit Mine Slope with Heterogeneous Complex Rock Mass

To ensure that the mining steps of deep concave open-pit coal mines with heterogeneous complex rock masses in arid areas are safely bounded by the design requirements and form a fixed side wall, to avoid the occurrence of instability and disaster caused by blasting vibration, based on non-homogeneous rock mass structure, lithology characteristics, fracture surface composition, morphology and joints, analysis of fissure development trend, and case studies of wedge-shaped landslide accident caused by blasting vibration, we proposed: (1) The pre-split instantaneous denotation charge is the dosage used for the segment unit charge of the primary blast hole and buffer hole, and it’s used for calculating . Based on this, the time intervals of segmented detonating cord and fuse are calculated and the actual detonating unit charge is decided. (2) Leave lateral free surface on the fixed side boundary and drill inclined blast holes along the slope of the steps, connect detonating cords to the blasting network, multi-point instantaneous detonate uncoupled segmented charge holes, use the pre-crack and fracture surface to reduce the damage caused by the explosion shock wave of the primary and buffer blasting holes. (3) The main blast hole and buffer hole are connected by non-conductive detonating cord and “four-way” blasting network, couple continuous concentrated charge using non-conductive detonating cord and fuse plus or detonator plus segmented ammonium dynamite initiator and expanded ammonium oil charge for millisecond interval detonation. Control the number of blasting holes and unit detonating charge over equal segments of fuse and detonating cord, reduce the impact of close-range blasting vibration of vertical deep holes on fixed side wall and step slope. Results of the blasting experiment show that using the technology of detonating cord in combination with non-conductive detonator’s pre-split hole millisecond differential blasting network plus reserved free face and segmented unit charge detonation, provide 1-2 blasting lateral free face or positive free face, making the blasting effect dispersed around the blasting hole. It has better solved the major safety problem of instability and disaster caused by the blasting effect on the fixed border-to-boundary steps of deep concave open-pit mine in arid region.

Numerical investigation of the shockwave overpressure fields of multi-sources FAE explosions

Shockwaves from fuel-air explosive (FAE) cloud explosions may cause significant casualties. The ground overpressure field is usually used to evaluate the damage range of explosion shockwaves. In this paper, a finite element model of multi-sources FAE explosion is established to simulate the process of multiple shockwaves propagation and interaction. The model is verified with the experimental data of a fourfold-source FAE explosion, with the total fuel mass of 340 kg. Simulation results show that the overpressure fields of multi-sources FAE explosions are different from that of the single-source. In the case of multi-sources, the overpressure fields are influenced significantly by source scattering distance and source number. Subsequently, damage ranges of overpressure under three different levels are calculated. Within a suitable source scattering distance, the damage range of multi-sources situation is greater than that of the single-source, under the same amount of total fuel mass. This research provides a basis for personnel shockwave protection from multi-sources FAE explosion.

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.

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.

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.

Experimental Study Comparing the Effectiveness of Physical Isolation and ANN Digital Compensation Methodologies at Eliminating the Stress Wave Effect Error on Piezoelectric Pressure Sensor.

Stress wave, accompanied by explosion shock wave overpressure measurement and dynamic pressure calibration on shock tube, could cause error signals in the piezoelectric pressure sensor (PPS) used for measuring and calibrating. We may call this error the stress wave effect (SWE). In this paper, the SWE and its isolation from PPS were studied by using a split Hopkinson pressure bar (SHPB). In the experimental study of SWE, when increasing the input stress, the corresponding output signal of the PPS was analyzed, and the existence of SWE was verified using the result of the spectrum analysis of the output signal. The stress wave isolation pedestal used in the stress wave isolation experiment was made of nylon and plexiglass polymer materials. The effects of the isolation pedestal’s materials and length on the stress wave isolation were analyzed using the study results. Finally, an artificial neural network (ANN) was trained with the data of the SWE study and was further applied to compensate the SWE error of the PPS output signal. The compensating results were compared with the isolating results, and the advantages and disadvantages of the digital compensation and physical isolation methods were analyzed.

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.

Numerical analysis of the interaction of two underwater explosion bubbles using the compressible Eulerian finite-element method

This paper presents numerical investigations of the nonlinear interactions between two underwater explosion (UNDEX) bubbles using the compressible Eulerian finite-element method (EFEM). The volume of fluid method is applied to capture the multi-fluid interface. In this model, the high-temperature and high-pressure gaseous products inside the UNDEX bubble are described by the equation of state for Jones–Wilkins–Lee, which allows us to consecutively simulate the propagation of the primary explosion shock wave and multi-period bubble pulsations. To verify the efficiency and accuracy of the present model, comparisons with experimental data are performed, showing that both the dynamic behaviors of oscillating bubbles and the pressure profiles of primary shock waves, bubble pulsations, and jetting loads are highly consistent. In addition, it is found that the EFEM model can satisfactorily reproduce the complex characteristics of interacting bubbles, such as the coalescence and splitting that occur during later pulsating cycles in bubbles. On this basis, the effects of the initial bubble–bubble distance γbb and buoyancy parameter δ on the features of bubble interactions and the corresponding pressure loads in the flow field are analyzed and discussed. In particular, the pressure induced by two identical UNDEX bubbles (each generated by detonation of an explosive with weight W) is compared to that induced by a single bubble generated by an explosive with weight W or 2W to provide the basic technical support and reference for the design of multiple-weapon attacks in military engineering applications.

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.

Wave-Blocking Characteristics of Corrugated Plates under Explosion

Corrugated-board explosion-proof wall is the main means to prevent explosion shock wave damage, and it is important to study the effect of different corrugated plates on the shock wave. Using a high-speed schlieren experimental system and an air overpressure test system, the wave-blocking characteristics of different forms of corrugated plates are comprehensively studied. The schlieren images were used to analyze the influence that the corrugation shape of a corrugated plate has on the shock wave propagation characteristics. The results show that the reflection process of the triangular-, trapezoidal-, and half-cylindrical-shaped corrugated plates exhibit differences. The number of reflected waves from the triangular corrugated plate is much greater than that from the other corrugated plates, and it will consume more energy. The diffraction wave-front velocity has a trend of initially decreasing and then increasing and is also reduced by different degrees by the reflection. Comparative analysis of the schlieren images and the air shock wave overpressure test shows that plates corrugated with different corrugation shapes decrease the diffraction overpressure peak and exhibit a hysteresis.

Numerical Studies on the Heat Effect of Explosion Suppression by a Heat Pipe

A composite structure with a heat pipe and foamed iron-nickel composite fire suppression is proposed on the basis of the phase-change heat transfer of the heat pipe, which simultaneously attenuates the metal foam explosion energy. A numerical simulation is conducted to evaluate the feasibility of the designed construction for suppressing explosions under various thicknesses and pore diameters of the metal foam. The results demonstrate that when the foam iron-nickel metal is installed in the pipeline, the temperature reduction rate in the pipeline can reach 8.9%. The new heat pipe foam composite structure can reduce the flame temperature to 1600 K within 0.095 s. It is concluded that the heat pipe composite metal foam structure pipeline has a strong effect on suppressing combustion and explosion overpressure. Due to the combined effect of the heat pipe vacuum chamber suction energy and the foamed iron-nickel, the flame temperature decay rate increases. The maximum attenuation rate of the foamed iron-nickel for the gas explosion shock wave reaches 41.76%, and the maximum flame temperature attenuation rate reaches 64.7%. The composite heat pipe structure can quickly disperse and transfer heat, thereby effectively destroying the heat storage environment as soon as possible to prevent a secondary explosion from occurring.

Research on Attenuating Mechanism of Wave-eliminating Interceptor on Explosion shock wave in Tunnel Engineering

The research on the explosion shock wave propagation and attenuation technology in tunnel engineering had been a hot issue at home and abroad. The installation of a series of wave-eliminating interceptor in tunnel engineering was beneficial to attenuate explosion shock wave in tunnel engineering. It was rapidly achieved to attenuate the explosion shock wave. In this paper, based on the clarification of the propagation law explosion shock wave in air, explosion load in tunnel engineering was analysed. And the waveform characteristics and propagation law of explosion shock wave were revealed. Then the rectification mechanism was got. The interaction between the explosion shock wave and the interceptor was analysed. Then the reflection mechanism and the disturbing mechanism were obtained. With the numerical simulation method, the propagation law of explosion shock wave under different angles of the interceptor was studied. The attenuation law of explosion shock wave was revealed. The optimal angle of interceptor was achieved.

Interaction between shock wave and a movable sphere with cavitation effects in shallow water

In this paper, we establish a fluid-structure interaction (FSI) model to investigate the dynamic interactions between the underwater explosion (UNDEX) shock wave and a movable sphere near the free surface. We utilize the local discontinuous Galerkin (LDG) method to capture the propagation of the shock wave in the fluid domain and employ the pressure cutoff model to calculate cavitation effects. The fluid elements at the fluid-structure interface are directly coupled to the structural dynamic model, and the structural transient dynamic responses are coupled with fluid acoustic pressure at the fluid-structure interface in the governing equation. The validity of the present FSI model is verified by comparing with the continuous Galerkin method. Due to the advantage of the LDG method in capturing the discontinuous wave, the present model shows better properties than the traditional coupled acoustic-structural model. With the present FSI model, we investigate the interaction between the UNDEX shock wave and a submerged and floated sphere. Under the combined effects of the free surface and structure, the UNDEX shock and cavitation loading characteristics are analyzed, and the influences of complicated cavitation effects on dynamic responses of the sphere are discussed.

Determination of the Danger Area under the Effects of the Explosive Shock Wave

Determination of the Danger Area under the Effects of the Explosive Shock Wave

MODELING OF BLAST EFFECTS ON UNDERGROUND STRUCTURE

Modeling of the impact of a point explosion shock wave on a soil mass and an underground structure at different locations of the explosion epicenter from the ground surface was performed. The study of the stress- strain state of soils was carried out usi ng a nonlinear dynamic method and a fully coupled numerical model, in­cluding various models of materials. The result of numerical modeling showed the adequacy of the adopted nu­merical calculation methods. The findings showed that solving the problem in a nonlinear dynamic formulation allows obtaining the parameters of the shock wave at different depths from the explosion center, as well as ob­taining a complete picture of the interaction of the shock wave with the underground structure in surface and un­derground explosions.