Shock Wave Overpressure Research Articles

Influence of length and angle of bifurcated tunnel on shock wave propagation

In order to study the influence law of bifurcated tunnel on the overpressure propagation of gas explosion shock wave, the variation law of overpressure of shock wave in main tunnel under different lengths and included angles of bifurcated tunnel was studied by numerical simulation. The results showed that: 1) the length of bifurcation tunnel had different effects on shock wave propagation when the bifurcated tunnel was opened and closed. The length of the bifurcated tunnel had no effect on the shock overpressure in the main tunnel, when the bifurcated tunnel was opened. When the bifurcated tunnel was closed, the length of the bifurcated tunnel had a great influence on the shock wave overpressure in the main tunnel, showing a tendency of decreasing first and then tending to be stable. When the included angle of the bifurcation tunnel was 45°, the overpressure at the monitoring point decreased from 368.7 kPa to 291.5 kPa, with a decreasing rate of 28.6%, and then fluctuated slightly around 291.5 kPa 2) The bifurcation of bifurcated tunnel had a consistent effect on the peak overpressure of shock wave despite of the opening and closing of bifurcated tunnel. The shock wave overpressure in the main tunnel increased first and then decreased with the increase of the included angle of the bifurcated tunnel, and the peak overpressure was the highest when θ = 90°, with 333.1 kPa for open and 333.4 kPa for closed. When 45° < θ < 90°, the shock wave overpressure in main tunnel increased rapidly with the increase of angle, with an increase rate of 14.3%. When 90° < θ < 135°, shock wave overpressure slowly decreased with the increasing of angle, with a decreasing rate of 2.9%. 3) In numerical simulation of gas explosion, the geometric model of tunnel net can be reasonably simplified according to the influence law of the length of bifurcated tunnel on the shock wave of main tunnel. The end of emergency lane and other chamber should be arranged 50 m away from the crossing point.

Synergistic effects on the physical effects of explosions in multi-hazard coupling accidents in chemical industries

One of the challenges of the multi-hazard coupling risk assessment is synergistic effects. This research performed experiments and numerical simulations, aiming to analyse the synergistic effects on the physical effects of explosions. The direct influences of atmospheric temperature and density on the propagation of explosion shock waves were explained and quantified through function fittings. Shock wave velocity will increase with the increase of atmospheric temperature and the decrease of atmospheric density. On the other hand, shock wave overpressure will decrease with the increase of atmospheric temperature, but not be significantly influenced by the density. The indirect synergistic effects on explosion physical effects were also explained through the analysis of the phenomena in the experiments and simulations. Temperature and density gradients could cause inhomogeneous velocity distribution and change the shapes of the shock wave fronts, thereby influencing the reflection and changing the shock wave overpressure. Based on the experimental and simulative results, the direct and indirect influences of the synergistic effects on consequence analysis and risk assessment were analysed in explosion-toxic-fire coupling accident scenarios. This research provides a multi-hazard idea for synergistic effect research, and can also be instructive for the risk assessment and safety management in chemical industries.

Influence of coal seam gas pressure on the propagation mechanism of outburst two-phase flow in visual roadway

Coal and gas outbursts are serious disasters that occur during coal mine production. In these instances, the outburst two-phase flow is the main cause of casualties. To investigate the propagation and mechanism responsible for the disaster of the outburst two-phase flow, a visual test system for coal and gas outburst simulation was independently developed. The outburst simulation experiments under different gas pressures were carried out and the propagation process of outburst two-phase flow in a visual roadway was monitored in real time to analyze the propagation mechanism and outburst intensity. The experimental results showed that the first shock wave overpressure reached its peak value immediately after the outburst and the characteristics of turbulent pulse appeared at the front of the outburst cavern, which was followed by one to two successive waves with lower peak values in the negative-pressure region. The flow pattern of pulverized coal observed in the visual roadway included suspended, stratified, dune, and plug flows. The velocity of pulverized coal flow was calculated based on the image method, which can be divided into the acceleration phase, and the acceleration and deceleration cycling phases. When the gas pressure increased from 0.35 MPa to 2.0 MPa, the velocity of pulverized coal flow increased from 34.19 m/s to 71.20 m/s, while they had a nonlinear relationship. The shock wave propagated in the roadway ahead of the pulverized coal flow at supersonic speed, and the velocity of shock wave front was as high as 344.75–370.02 m/s, which was much higher than that of pulverized coal flow. The higher the gas pressure was, the more pulverized coal ejected, and the relative outburst strengths increased from 36.1% to 63.7% with the increase of gas pressure from 0.35 MPa to 2.0 MPa.

Numerical simulations of trajectories of shock wave triple points in near-ground explosions of TNT charges

To accurately predict the locations and trajectories of shock wave triple points in near-ground explosions, this study determined the propagation law of shock waves after the initiation of a detonator using a schlieren system. Moreover, it established a numerical simulation model using the Autodyn software and verified the accuracy of the model through a detonator explosion experiment. The propagation law of shock waves of TNT charges (1, 10 ​kg and 100 ​kg) at different heights of burst(0.5, 1.0, 1.5, 2.0 ​m,and 2.5 ​m) was studied through numerical simulations, and the triple point trajectories were fitted to an empirical formula. The results show that the maximum simulation error relative to the schlieren images of detonator explosions did not exceed 4 ​mm. As the scaled height of burst decreased, the positions of generated triple points were closer to the vertical projection of the explosion center and rose faster. As the scaled distance increased, the scaled height of triple points rose exponentially. The average error of triple point trajectories between the values predicted in this study and the experimental values was 4.1%, indicating that the accuracy of the fitted formula is acceptable. This study revealed the overpressure distribution law of shock waves and will provide a reference for shock wave overpressure measurements and explosion protection.

A Numerical Study on the Blast Wave Distribution and Propagation Characteristics of Cylindrical Explosive in Motion

In order to study the overpressure distribution law of a shock wave under the dynamic explosion of a cylindrical charge and the influence of the charge speed on the overpressure distribution law, a trinitrotoluene (TNT) cylindrical bare charge was selected. Additionally, a numerical simulation of a cylindrical charge explosion under different motion speeds was carried out using the AUTODYN finite element software. The results showed that during the static explosion of a cylindrical charge, the shock wave propagates outward in the form of an ellipsoid, whereas under the dynamic explosion, the shock wave overpressure field is an irregular ellipsoid, and the shock wave overpressure zone shifts to the velocity direction. With an increase in the charge velocity, the peak value of the shock wave overpressure increases gradually in the moving direction. The simulation data were analyzed, revealing that the calculation model of the dynamic explosion shock wave overpressure field of a cylindrical charge with a scaled distance of 1 m·kg−1/3 ≤ R ¯ ≤ 1.5 m kg−1/3 can provide a reference basis for the study of dynamic explosion shock waves.

Research on the distribution characteristics of explosive shock waves at different altitudes

There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes. At present, there are many studies on plain explosion shock waves, but there are few studies on the distribution characteristics of plateau explosion shock waves, and there is still a lack of complete analysis and evaluation methods. This paper compares and analyzes shock wave overpressure data at different altitudes, obtains the attenuation effect of different altitudes on the shock wave propagation process and proposes a calculation formula for shock wave overpressure considering the effect of altitude. The data analysis results show that at the same TNT equivalent and the same distance from the measuring point, the shock wave overpressure at high altitude is lower than that at low altitude. With the increase in the explosion center distance of the measuring point, the peak attenuation rate of the shock wave overpressure at high altitudes is smaller than that at low altitudes, and the peak attenuation rate of the shock wave overpressure at high altitudes gradually intensifies with increasing proportional distance. The average error between the shock wave overpressure and measured shock wave overpressure in a high-altitude environment obtained by using the above calculation formula is 11.1389%. Therefore, this method can effectively predict explosion shock wave overpressure in plateau environments and provides an effective calculation method for practical engineering tests.

Effects of underwater explosion depth on shock wave overpressure and energy

In this paper, the effects of the water depth on the overpressure (pressure difference between positive shock pressure and hydrostatic pressure) peak and energy of underwater explosion shock waves were analyzed. Two quantitative calculation models were established that accounted for the effect of the water depth, which have theoretical and practical engineering value. A simulated deepwater explosion tank test was first conducted to obtain experimental data of the overpressure peaks and energies of the explosion shock waves generated by 10 and 30 g trinitrotoluene (TNT) explosives in a simulated environment at water depths of 400, 500, and 600 m. A one-dimensional wedge-shaped Euler grid numerical model was established to simulate the underwater explosion using the Autodyn software. The simulation model was validated by the experimental data to prove its accuracy and rationality. Then, numerical simulations were carried out at 13 operating conditions with 30 g of TNT in a full water depth range of 0–5000 m. Based on the simulation data analysis, the calculation models of the overpressure peak and energy flow density of the underwater explosion shock wave were obtained, which contain water depth correction functions. The results show that both the overpressure peak and the shock wave energy decreased with increase in the water depth, but the reduction percentage of the overpressure peak with the water depth was very small. The overpressure peak and energy flow density of the shock wave agreed with the explosion similarity law at all fixed water depths. The proposed calculation models have practical engineering value and generalization ability.

Influence of Roadway Cross-Section Shape on Gas Explosion Shock Wave Law in U-Type Ventilation Working Faces

In U-shaped ventilation working face, different tunnel section shapes are one of the important factors affecting the propagation of gas explosion shock wave. In order to study the propagation law of gas explosion shock wave in working face, the numerical simulation study was carried out by using Fluent simulation software combined with the actual situation of gas explosion in #415 working face of Chenjiashan Coal Mine in Shaanxi Province. By constructing a three-dimensional mathematical and physical model, a simulation study of the upper-corner gas explosion was carried out. The results are described as follows. (1) After the gas explosion shock wave propagates 40 m, the overpressure peak equidistant difference tends to be stable and attenuates and propagates in the form of a single shock wave. The study determines that the effective length of the U-shaped ventilation inlet/return tunnel is 40 m. (2) When the tunnel section is trapezoidal, the initial overpressure of the gas explosion shock wave propagating to the inlet/return airway is the highest, followed by rectangular and semicircular arches, but the internal overpressure attenuation trend of different cross-sectional shapes is the same. (3) The gas explosion shock wave propagates radially along the working face section during the working face propagation. The farther away the location is from the upper corner of the tunnel during a gas explosion with different cross-sectional shapes, the closer the cutoff overpressure peak is. The attenuation trend of overpressure with the propagation distance conforms to the power function law. The research results provide an important theoretical direction for the numerical simulation of gas explosions in coal mining faces.

The influence of sensor installation angle on explosive shock wave overpressure test

In the engineering measurement of explosion shock wave pressure, the installation method of shock wave pressure sensor is of great significance to accurately obtain shock wave pressure. Based on the actual shooting range explosion shock wave overpressure test program, this paper uses AUTODYN to establish a finite element numerical simulation model. The distance from the ground reflection pressure sensor to the explosion center is 3 m, 4 m, 5 m, and 6 m. The shock wave overpressure data in the range of 8° and 10° are acquired and analyzed. The analysis results show that the shock wave overpressure obtained when the sensor installation angle is absolute zero is the ideal value. When the sensor installation plate is within a certain range, the overpressure value of the explosion shock wave increases with the increase of the installation angle of the plate, and the installation angle of the sensor is positively correlated with the overpressure of the explosion shock wave.

Blast wave characteristics of multi-layer composite charge: Theoretical analysis, numerical simulation, and experimental validation

This article investigates the characteristics of shock wave overpressure generated by multi-layer composite charge under different detonation modes. Combining dimensional analysis and the explosion mechanism of the charge, a peak overpressure prediction model for the composite charge under single-point detonation and simultaneous detonation was established. The effects of the charge structure and initiation method on the overpressure field characteristics were investigated in AUTODYN simulation. The accuracy of the prediction model and the reliability of the numerical simulation method were subsequently verified in a series of static explosion experiments. The results reveal that the mass of the inner charge was the key factor determining the peak overpressure of the composite charge under single-point detonation. The peak overpressure in the radial direction improved apparently with an increase in the aspect ratio of the charge. The overpressure curves in the axial direction exhibited a multi-peak phenomenon, and the secondary peak overpressure even exceeded the primary peak at distances of 30D and 40D (where D is the charge diameter). The difference in peak overpressure among azimuth angles of 0–90° gradually decreased with an increase in the propagation distance of the shock wave. The coupled effect of the detonation energy of the inner and outer charge under simultaneous detonation improved the overpressure in both radial and axial directions. The difference in peak overpressure obtained from model prediction and experimental measurements was less than 16.4%.

Free-field shock-wave test method for meteorological air cannons

In this paper, a piezoelectric-sensor-based free-field shock-wave test method for measuring the muzzle overpressure of a meteorological air is proposed. The test system is described, and the measurement-point layout is introduced. Experimental verification of the results from Autodyn numerical simulations based on the Sadowski formula was conducted, and the distributions of pressure, density, and velocity of the muzzle flow field were simulated as references for the free-field shock-wave pressure for the actual tests. The experimental results from different models of air cannons demonstrate that the proposed method can accurately measure the peak of the free-field shock-wave overpressure. Considering the location of each sensor and the time interval between the shock-wave overpressure peak reaching adjacent test points, the propagation speed can be obtained, and the muzzle-pressure propagation law can be established. This work has certain guiding significance for the development and design of meteorological air cannons.

Research on bubble jet of underwater explosion at the bottom of fixed square plate

<p indent=0mm>The water jet formed after the collapse of the bubble in the near-field underwater explosion can cause serious damage to the local structure of the ship, and the formation of the jet is asymmetric, which makes it difficult to measure its data in the experiment. At present, studies on the pressure time history curves of the bubble jet in the underwater explosion are still relatively rare. In order to study the characteristics of the jet, the underwater explosion test of <sc>2.5 g</sc> TNT explosive at the bottom of fixed square plate at different detonation distances was carried out. First, the accuracy of the test data was verified by the underwater pressure sensor. Second, the image of the whole process from the explosive initiation to the bubble jet generated by the action of the bubble and the steel plate was obtained by high-speed camera. Finally, the time-history curve of water jet pressure was measured by the wall pressure sensor in the center of the steel plate, and another group of wall pressure sensors was set <sc>15 cm</sc> away from the center of the steel plate as a control group to ensure that the measured jet data were not clutter. The test data recorded by the underwater sensor show that the error between the shock wave overpressure, the maximum bubble radius of the bubble pulse period and the empirical formula is within 10%. The results recorded by the high-speed camera and wall pressure sensor show that three jets can be observed when the burst distance is <sc>28 cm,</sc> but the pressure time history curve is not measured due to the long burst distance. When the burst distances are <sc>15,</sc><sc> 17.5</sc> and <sc>20 cm,</sc> three jet pressure time history curves are measured. However, due to the short burst distance and the presence of a large number of bubbles between the steel plate and the water surface under the action of the shock wave, it is difficult to observe the test phenomenon with high-speed cameras. The pressure time history curve shows that three jets are generated after the first bubble pulse peak, and the jet pressure can reach 1/4 of the shock wave. The jet appears 1–3 ms after the first bubble pulse peak, and the time interval of each jet is between <sc>0.9</sc> and <sc>2.4 ms.</sc> The duration of jet load is between 4–27 μs, and it is greatly reduced as the distance increases.

Research on the Decompression Effects of Shaft Explosion-Proof Door at Different Lifting Heights

To study the decompression effects of shaft explosion-proof door at different lifting heights, this paper designed the gas explosion testing system. Based on the test results, this paper made a numeric analysis of the change regularities of the shock wave overpressure when the shaft explosion-proof door was lifted at different heights. Finally, this paper determined the proper lifting height of the shaft explosion-proof door and put forward the active decompression concept. The research showed that (1) the shock wave overpressure at the explosion-proof door decreased in a power exponential relationship as the lifting height increased. When the lifting height increased from 0 cm to 5 cm, the peak overpressure at the explosion-proof door decreased from 36.06 kPa to 22.47 kPa, dropping by 37.7%. When it was lifted at a height of 40 cm, the overpressure dropped to 11.20 kPa and the decompression reached 68.9%. (2) The overpressure at the ventilator decreased in a power exponential relationship as the lifting height increased. When the lifting height of the explosion-proof door increased from 0 cm to 5 cm, the decompression ratio reached the maximum 18.4%. After that, the decompression effect became worse and worse. (3) The explosion-proof door could depressurize and protect the ventilator at gas explosion but with limited effects. To protect the ventilator and the explosion-proof door to the maximum, it was suggested that the pressure sensor was set up somewhere in the mine where the gas explosion is likely to occur. In this way, the explosion was sensed in time and the explosion-proof door could be actively lifted for decompression. This paper was of great guiding significance in optimizing the design of the explosion-proof door equipment, reducing the loss of gas explosion accidents as well as carrying out the emergency rescue.

Impact of explosive charge mass on reflected shock wave of high explosion

Overpressure is an important metric of the destructive effect of the shock wave produced by high explosion. Investigating the overpressure of shock wave on the surface is an essential way for evaluating the power of explosive device. This study has important implications for quantitative analyses for establishing the relationship between parameters of reflected shock wave by using the numerical simulation software AUTODYN with different TNT explosive charge mass. The research indicates that with the increase of explosive charge mass, the initial value of peak overpressure of high explosive increases and the attenuation rate accelerates, it also provides the condition that the similarity law can be established in the relationship between peak overpressure and scale distance.

Influence of Chamber Geometrical Parameters on Suppressing Explosion Propagation

In this article, the effect of a chamber’s geometrical parameters on suppressing gas explosion propagation was studied. Three rectangular chambers were used in the study, with a constant length of 0.5 m, a constant height of 0.2 m, and a variable width of 0.3 m, 0.5 m, and 0.8 m; each chamber was installed in a pipeline system for experimental research. The experimental results showed that when the chamber length and height were fixed at 0.5 m and 0.2 m, respectively, the suppression effect of the chamber on the explosion shockwave improves with the increase in the chamber width; when the chamber width increases to 0.8 m, the chamber has suppressive effect on explosion shockwave propagation. It was also found that the suppression effect of the chambers on the explosion flame improves with the increase in the chamber width; when the width of the chamber is 0.5 m, the chamber effectively suppresses explosion flames. Based on the experimental results, a numerical model was established to simulate the suppression effect of five types of chambers with a length, width, and height of 0.5 m × 0.3 m × 0.2 m, 0.3 m × 0.5 m × 0.2 m, 0.5 m × 0.5 m × 0.2 m, 0.5 m × 0.8 m × 0.2 m, and 0.8 m × 0.5 m × 0.2 m, respectively. The numerical simulation results indicated that when the chamber length and height are constant at 0.5 m and 0.2 m, respectively, the suppressive effect of the chamber on the shockwave improves as the chamber width increases; when the chamber width increases to 0.8 m, the shockwave overpressure at the chamber outlet is attenuated by 10.61%, indicating that the chamber suppresses the propagation of explosion shockwave, which is consistent with the experimental results obtained in the study. It was also found that when the chamber width and height were constant at 0.5 m and 0.2 m, respectively, as the chamber length increases, the overpressure increases first and then weakens. When the chamber length increases to 0.8 m, the overpressure at the chamber outlet is attenuated by −14.16%, indicating that the chamber is not able to suppress the propagation of explosion shockwave. Finally, a numerical simulation of the propagation process of a methane-air mixture and explosion flames in different chambers was performed to analyse the effect of chamber geometrical parameters on explosion suppression effect.

Numerical simulation on interaction between blast shock wave and human thorax

The finite element model for simulating the interaction between blast shock wave and human thorax is established to analyze the propagation characteristics of stress wave in human thorax and the dynamic response of human thorax. The shock wave at the front of thorax is reflected by thorax surface and has the highest peak overpressure. The shock wave on the back of thorax is superimposed by diffraction shock waves from two sides of thorax and has the smallest peak overpressure. The overpressure of diffraction shock waves on both sides of thorax is similar. Due to the difference of impedance characteristics of thorax materials, the lung near the explosive point is mainly affected by compression waves transmitted by the incident shock wave through the muscles and sternum. The side lung is affected by the weak extension wave caused by the deformation of the sternum and the strong compression wave caused by the incident shock wave. In addition to the similar conditions of the side lung, the back of the lung is also subjected to compression waves caused by the reflection of vertebra. The relationship between the pressure on thorax surface and various tissues and the deformation speed of thorax and the blast shock wave can be fitted as y = A [ 1 − exp ( x B ) ] , where y is the dependent variable, x is the peak overpressure of blast shock wave, and A and B are the fitting constants.

Damage assessment of prefabricated prestressed channel slab under plane charge blast

The study of the mechanical properties of prestressed concrete channel slabs under different plane charge air blasts for applications in civil defense engineering is significant. For this reason, similar simulation tests were conducted on the anti-explosive performance of three 1:3 scale prestressed concrete channel slabs under 9 times plane charge air blast. The positive duration was more than 260 ms to simulate the uniform distribution load of a strong blast air shock wave on the prestressed concrete channel slab. The results showed that the designed prestressed concrete channel slab had good displacement ductility without brittle destruction, which significantly reduced the damage of the blasting impact on the structure. The channel slab could resist an air shock load of 0.467 MPa without damage. On the other hand, the positive duration was not only related to the quality of the overlying soil but also related to the air shock wave overpressure design value. The channel plate is regarded as a rigid-plastic component to calculate its plastic dynamic response under explosive load. In addition, the reliability of the theoretical calculation results and ABAQUS software simulation were verified by experimental data, which provided a feasible analytical method for calculation and simulation research in civil air defense engineering.

Experimental study on shock wave from dynamic explosion of a warhead based on seismic wave triggering

A method for measuring the shock wave overpressure of blasting warhead explosion based on seismic wave triggering was proposed. By the proposed method, the peak overpressure of the blast wave from dynamic explosion of a warhead can be obtained reliably. The air explosion shock waves of the blasting warhead with the target velocities of 0, 535 and 980 m/s were measured, respectively. And the measured results of the peak overpressure of the shock wave from dynamic explosion of the blasting warhead were compared with those by the empirical formula calculation. The influence of warhead velocity on the pressure field distribution of the shock wave was analyzed quantitatively. Finally, a three-dimensional visualization model for shock wave overpressure from dynamic explosion of the warhead was reconstructed by using the thin-plate-spline interpolation method. The reconstructed model can provide a basis for studying the characteristics of dynamic explosion shock wave based on the measured data in the complex environment of an actual combat.

Research on anti-shockwave performance of the protective equipment for the head of a soldier based on shock tube evaluation

In order to optimize the structure and improve the performance of the head and face protective equipment for an individual soldier, firstly, the blast wave resistance tests of the bare-head model were carried out in real explosion field and shock tube environments, respectively. On this basis, the forward and lateral blast shockwave protective performance tests for helmet-head systems with different structures and protection levels were carried out by using the shock tube method. Finally, the peak values and durations of shockwave overpressure in the front, forehead, top, back, ear and eye areas of the helmet-head systems were compared and analyzed. The experimental results show that the blast shockwave test using a shock tube can be a substitute for the real explosion field test. When subjected to the effect of frontal shock wave, the peak value of the shockwave overpressure measured at the top measuring point of the two-half-helmet head model is about 1/6 compared with that of the nozzle outlet and 1/3 of the bare-head model as well as the integrated-helmet head model. The shockwave splits and relieves pressure at the split structure on the top of the two-half helmets and forms a superimposed reflection, resulting in a prolonged action time (5.5−8.5 ms), but a significantly decreased peak overpressure. For the rear measuring points, the peak overpressure (365 kPa) of shockwave measured by the integrated-helmet head model is slightly higher than that (303 kPa) measured by the two-half-helmet head model, and about 2.5 times as high as that (148 kPa) measured by the bare head model. By improving the structural airtightness of individual head and face protective equipments (such as wearing glasses, earmuffs or protective masks), shockwaves can be effectively prevented from entering the helmet-head systems, the stacking convergence effect can be weakened, and the protective performance of individual head and face equipments can be improved.

Simulation of LPG tank truck leakage and explosion accident based on CFD

Road transportation of hazardous chemicals has a high risk and is likely to cause serious road traffic accidents. In this paper, the most common LPG tanker in hazardous chemical transportation is taken as the research object. Based on theCFD method, we used FLACS software to simulate LPG tank car accident in Italy. The leakage process of LPG tank car after leakage was simulated, and the diffusion process of propane and butane mixture in one minute when the accident occurred. It was further analyzed that the leakage material exploded when it encountered the ignition source, and the shock wave overpressure was the highest at 2.5 seconds after the explosion, with the shock wave pressure exceeded 0.26MPa. Also, the attenuation of theblast wave is higher in the area far away from the explosion source. The research results can provide effective data support for on-site emergency disposal and personnel evacuation of similar accidents.