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During missions or in tactical field, vehicles are subjected to various threats: penetrating projectiles, shape charge ammunitions, but more frequently to mines and improvised explosive devices. This paper presents a small-scale, experimental and numerical study on blast wave effects of explosive charges on vehicles' floor. Two types of steel plates are studied in order to define the concept of protection factor for tactical field vehicles subjected to blast loadings. The results are used to establish a series of mathematical formulas to rate the protection factor. [ABSTRACT FROM AUTHOR]

Pipelines that are buried in ground are used for transference of water and energy sources. These lines are considered infrastructures and have a high importance. In this paper behavior of soil and pipes are simulated using the finite-element based software ABAQUS, and effect of blast wave on the amount of tension and displacement of a pipe is investigated. The simulations are run for the pipe's substance, burial depth, dimension, and also the intensity and situation of the explosion. AUTODYN software is used for evaluation of blast wave's power. Simulation results show the positive effect of increasing the pipe's dimension and burial depth on reducing the destruction caused by explosion. [ABSTRACT FROM AUTHOR]

Bare, cylindrical, explosive charges produce secondary shock waves in the direction of least presented area. Whilst the source of these shock waves was explored in the 1940's, no attempt was made to predict them. This paper describes the detonation of bare, cylindrical charges of PE4 (RDX binder 88/12 %), mass 0.2 to 0.46 kg and with a length to diameter ratio of 4 to 1. High speed camera footage showed (i) the formation of the separate, primary, shock waves from the sides and ends of the charge, (ii) Mach reflection of these separate shock waves, giving rise to reflected, secondary shock waves, and (iii) the secondary shock waves catching and merging with the primary shock wave. In the axial direction, the secondary shock wave's peak overpressure and impulse exceeded that of the primary shock wave for scaled distances, Z= R/ M1/3 ≥3.9 m kg−1/3, where M is the mass in kg and R the distance from the charge in m. It was found possible to predict the primary peak overpressure, P, at all distances in the axial direction, for a constant length to diameter ratio, using P=3075 Z−3−1732 Z−2+305 Z−1. Close in the primary peak overpressure is proportional to M/ R3 in the axial direction. It was not possible to predict the secondary peak overpressure with the data obtained. The total impulse from both shock waves, I, in the axial direction can be predicted using I=746( M2/3/ R)3−708( M2/3/ R)2+306( M2/3/ R). [ABSTRACT FROM AUTHOR]

Blast waves appear in many astrophysical phenomena, such as supernovae. In this paper we discuss blast waves with cosmic rays, i.e., with a component with a power-law number density distribution function N( p) ∝ p that may be particulary important in describing the evolution of supernova remnants. We confirm some previous findings that a significant amount of cosmic ray energy is deposited towards the center of a remnant. [ABSTRACT FROM AUTHOR]

SUMMARY Head injuries due to complex blasts are not well examined because of limited published articles on the subject. Previous studies have analyzed head injuries due to impact from a single planar blast wave. Complex or concomitant blasts refer to impacts usually caused by more than a single blast source, whereby the blast waves may impact the head simultaneously or consecutively, depending on the locations and distances of the blast sources from the subject, their blast intensities, the sequence of detonations, as well as the effect of blast wave reflections from rigid walls. It is expected that such scenarios will result in more serious head injuries as compared to impact from a single blast wave due to the larger effective duration of the blast. In this paper, the utilization of a head-helmet model for blast impact analyses in AbaqusTM (Dassault Systemes, Singapore) is demonstrated. The model is validated against studies published in the literature. Results show that the skull is capable of transmitting the blast impact to cause high intracranial pressures (ICPs). In addition, the pressure wave from a frontal blast may enter through the sides of the helmet and wrap around the head to result in a second impact at the rear. This study recommended better protection at the sides and rear of the helmet through the use of foam pads so as to reduce wave entry into the helmet. The consecutive frontal blasts scenario resulted in higher ICPs compared with impact from a single frontal blast. This implied that blast impingement from an immediate subsequent pressure wave would increase severity of brain injury. For the unhelmeted head case, a peak ICP of 330 kPa is registered at the parietal lobe which exceeds the 235 kPa threshold for serious head injuries. The concurrent front and side blasts scenario yielded lower ICPs and skull stresses than the consecutive frontal blasts case. It is also revealed that the additional side blast would only significantly affect ICPs at the temporal and parietal lobes when compared with results from the single frontal blast case. By analyzing the pressure wave flow surrounding the head and correlating them with the consequential evolution of ICP and skull stress, the paper provides insights into the interaction mechanics between the concomitant blast waves and the biological head model. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Blast and ballistic impacts are high-strain rate events that can cause catastrophic damage to structures and endanger human lives. Shielding materials play a critical role in mitigating the risk of injury and damage caused by such events. However, these materials must withstand extreme conditions of pressure, strain, strain-rate, multi-mode stresses, and temperature during impact. The development of novel structures and arrangements, including monolithic, hybrid, and high-performing fiber-reinforced polymers, requires advanced testing techniques to ensure their effectiveness in the field. This state-of-the-art paper reviews the latest experimental techniques for characterizing the impact resistance, shock energy absorption, high strain-rate responses and endurance of materials used for shielding. The paper provides dedicated sections on blast and ballistic impact experimentation techniques, covering diverse testing methods for various material classes and configurations used in shielding. It also discusses complex material mechanics during impact response, projectile classifications and characterizations, and the development of strategies for high-performing shielding configurations. Overall, this review provides a comprehensive overview of the latest experimental techniques for materials subjected to blast/ballistic impact scenarios, offering valuable insights for researchers and practitioners working on the design and testing of shielding materials. [Display omitted] • Experimental techniques for high strain rate characterization - Flyer plate test, Taylor test, Split Hopkinson Pressure bar tests, Drop hammer tests. • For blast characterization, shock tube experiments, charge detonation, ballistic pendulum reviewed. • For ballistic characterization, standards, projectile classifications and characterizations, X-ray computed tomography, Photon Doppler Velocimetry, VISAR reviewed. • Materials - high strength steels, aluminum alloys, ceramics, polymers, fiber reinforced composites, cementitious and cellular (auxetic) metamaterials. [ABSTRACT FROM AUTHOR]

In order to explore the influence of weak interlayer on blasting characteristics in natural rock mass, by using the particle flow code (PFC2D), a single hole blasting numerical model of hard rock with soft interlayer is established. The blasting experiments at different positions and thicknesses of weak interlayer are carried out. Then an in-depth analysis from the perspectives of crack effect, stress field and energy field is made. Results showed that: (i) When the explosion is initiated outside the weak interlayer, if the interlayer is located within about twice the radius of the crushing area, the closer the interlayer is to the blast hole, the higher the damage degree of the rock mass around the blast hole. And the number of cracks will increase by about 1–2% when the distance between the weak interlayer and the blast hole decreases by 0.5 m. (ii) When detonating outside the weak interlayer, if the interlayer is within about 4 times radius of the crushing area, the hard rock on both sides of the weak interlayer will in a high stress state. Under the same case, the peak kinetic energy and peak friction energy will increase by about 23 and 13%, respectively, and the peak strain energy will increase by about 218 kJ for every 0.1 m increase in the thickness of the weak interlayer. [ABSTRACT FROM AUTHOR]

The interaction between a molecular cloud and an external agent (e.g., a supernova remnant, plasma jet, radiation, or another cloud) is a common phenomenon throughout the Universe and can significantly change the star formation rate within a galaxy. This process leads to fragmentation of the cloud and to its subsequent compression and can, eventually, initiate the gravitational collapse of a stable molecular cloud. It is, however, difficult to study such systems in detail using conventional techniques (numerical simulations and astronomical observations), since complex interactions of flows occur. In this paper, we experimentally investigate the compression of a foam ball by Taylor–Sedov blast waves, as an analog of supernova remnants interacting with a molecular cloud. The formation of a compression wave is observed in the foam ball, indicating the importance of such experiments for understanding how star formation is triggered by external agents. [ABSTRACT FROM AUTHOR]

Copyright of Mechanika is the property of Mechanika and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the face of rapidly evolving challenges, new protection techniques against blast waves generated by high explosive detonations must be identified. The protection of vehicle floors is particularly relevant, especially against improvised explosive devices (IED), as these are challenging to detect. In this paper, investigations on fluid-filled sacrificial claddings are presented. Classical sacrificial claddings aim at limiting the deflection of the target by dissipating the blast wave energy through the core plastic or brittle deformation. On the contrary, fluid-filled sacrificial claddings are systems which aim at limiting the deflection of the target by extracting energy from the system and modifying the load distribution on the target. A new experimental set-up, designed for this investigation, is presented. Based on pressure signals, high speed-imaging and numerical simulations on LS-DYNA, it is shown that the ability to extract energy from the system is directly linked to the freedom of displacement of the fluid. It is also shown that at the same time, higher fluid displacement and well-designed boundary conditions lead to higher impulse spreading on the target. • Investigation of fluid-filled sacrificial claddings for the purpose of momentum control. • Design of a novel experimental setup for the measurement of impulse spreading in a water filled container. • Use of a numerical model for a broader understanding of impulse distribution on a target. [ABSTRACT FROM AUTHOR]

To present a feasibility of high-altitude flight of a laser-propelled vehicle at supersonic speed, we have developed a flight simulator which has fluid-orbit coupling calculation module to reproduce impulsive flight reaction driven by blast waves. By high-power energy transmission through arrayed lasers together with the genetic algorithm (GA) controlled sub-laser, the supersonic flight is successfully achieved in the simulation for 32.5-g vehicle, while the angular offset should be suppressed as small as possible. Rather than translational position, controlling angular offsets by the GA operation is especially important to attain the km-order flight on the premise of the active control. Additionally, the vehicle weight, the vehicle size, and the input energy are scaled up to assess the stable flight of 10-kg vehicle. The active control technique has enough possibility to launch kg-order vehicle at supersonic regime with the optimized beaming strategy. [ABSTRACT FROM AUTHOR]

The paper by J.M. Dewey (Shock Waves 29(4):583–587, 2019) described the development of an Excel-based interface that provides the physical properties of blast waves generated by propane/oxygen explosions. The interface was developed using the data from a nominal 20 ton explosion of an assumed stoichiometric propane/oxygen mixture. Comparisons of data from the interface with measurements of small-scale stoichiometric propane/oxygen explosions show discrepancies. Further studies revealed that the 20 ton explosion was not stoichiometric and had a 43% oxygen deficiency. The interface has been redeveloped assuming that only 57% of the available propane had been detonated. The revised interface produces results which agree with measurements from both the 20 ton explosion and the small-scale (< 1 g) detonations. The revised interface and updated users' guide are available for downloading. [ABSTRACT FROM AUTHOR]

We are concerned with spherically symmetric solutions to Euler equations for multi-dimensional compressible fluids which have many applications in diverse real physical situations. The system can be reduced to one-dimensional isentropic gas dynamics with geometric source terms. Due to the presence of the singularity at the origin, there are few papers devoted to this problem. The present paper proves two existence theorems of global entropy solutions. The first one focuses on a case excluding the origin in which negative velocity is allowed, and the second one corresponds to a case which includes the origin with non-negative velocity. The compensated compactness framework and vanishing viscosity method are applied to prove the convergence of approximate solutions. In the second case, we show that if the blast wave initially moves outwards and the initial densities and velocities decay to zero with certain rates near the origin, then the densities and velocities tend to zero with the same rates near the origin for any positive time. In particular, the entropy solutions in two existence theorems are uniformly bounded with respect to time. [ABSTRACT FROM AUTHOR]

The paper presents a study aimed at understanding the characteristics of an internal explosion within a chamber with limited venting. The study includes numerical simulations and analytical derivations. An in-house 3D code employing an improved weighted essentially non-oscillatory (WENO) conservative finite difference scheme was used to carry out the simulations. It is indicated that the proposed improved WENO scheme can resolve the shock waves with higher accuracy and resolution. Further, a simplified analytical model to predict the quasi-static overpressure was developed based on the conservation law of total energy and dimensional analysis theory. It is demonstrated that the proposed simplified approach for prediction of the quasi-static overpressure agrees well with simulation results for a wide range of explosive weights and venting hole sizes. The studies in this paper provide an efficient method to predict the blast load inside a partially confined chamber for the analysis of the consequences of explosion. [ABSTRACT FROM AUTHOR]

BLEVE (Boiling Liquid Expanding Vapor Explosion) phenomenon is one of the major industrial accidents observed in gas processing industry, which remains a major concern for risk decision-makers. BLEVE blast wave mechanism has been widely studied by several authors who proposed simplified approaches based on simple physical models or empirical correlations, but only few approaches including analytical solutions have been undertaken. Moreover, the simplified and empirical approaches are not very satisfactory because they overestimate overpressure measures. In this paper (Part I), an analytical model based on Sedov-Taylor blast wave solution and self-similar theory, which is of great interest in various fields of physics, is proposed for estimating BLEVE overpressure effects. The parameters characterizing the blast wave evolution (overpressure, radius and velocity) are established by applying the Vashy-Buckingham theorem (Pi theorem). To demonstrate the ability of the proposed model to deliver reliable predictions, a validation with large and medium-scale BLEVE experiments issued from the literature is carried out. Furthermore, a comparison with the TNT equivalent model and other models (empirical and simplified physical) is performed. The results of these comparisons are very encouraging and show good agreement in terms of precision. This is Part I of two papers, focusing on description and validation of the Sedov-Taylor blast wave model. Part II deals with application of the model on a LPG accumulator in an Algerian gas processing unit. [ABSTRACT FROM AUTHOR]

This paper investigates the applicability of direct simulation considering a stratified atmosphere to an unsteady analysis of a blast wave caused by a meteorite explosion. Axi-symmetric Euler equations with a gravity term that considers a horizontally stratified atmosphere are numerically solved to analyze blast wave propagation from the source of meteorite explosion to the ground. Computations are made to reproduce the blast wave generated by the Chelyabinsk meteorite in 2013, assuming a spherically uniform high-pressure and high-temperature core as the source of explosion. The amount of energy released by the explosion at an altitude of 25 km is assumed to be 500 kt of trinitrotoluene, and the computational domain ranges over a radial distance of 50 km from the center of the explosion. The simulation results in a uniform atmosphere agree well with the results of well-known Brode's empirical formula, and the blast wave obtained from the simulation considering a standard atmosphere is expected to cause serious damage to the ground, as experienced at the time of the Chelyabinsk event. Moreover, the simulation results clarify the characteristics of blast wave propagation through uniform, isothermal, and standard atmospheres. [ABSTRACT FROM AUTHOR]

With the increasing threat of terrorism attack, the probability of explosion inside the subway is very large. Reinforced concrete columns are the main supporting members of subway stations. If the columns of a subway station were subjected to near-field explosions, their damages can affect the safety of the subway after explosion. By using the finite element method, this paper established a coupling 'explosive-air-concrete' model and verified the feasibility of the model through experiments. This model can be used in the damage assessment of subway station columns in terms of the bearing capacity, by which the damage of a reinforced concrete column can be divided into different levels. Furthermore, the effect of different parameters on the damage and bearing capacity of the subway station is discussed. The results demonstrate that the stirrup reinforcement ratio of a reinforced concrete is the key factor in determining the column damage under blast loadings. The present study therefore provides a key reference for assessing the damage of subway structures after terrorist attack. [ABSTRACT FROM AUTHOR]

Blast waves generated by cylindrical TNT explosives in partially confined chamber were studied numerically and experimentally. Based on the classical fifth-order weighted essentially nonoscillatory finite difference schemes (fifth-order WENO schemes), the 1D, 2D, and 3D codes for predicting the evolution of shock waves were developed. A variety of benchmark-test problems, including shock tube problem, interacting blast wave, shock entropy wave interaction, and double Mach reflection, were studied. Experimental tests of explosion events in a partially confined chamber were conducted. Then, the 3D code was employed to predict the overpressure-time histories of certain points of chamber walls. Through comparing, a good agreement between numerical prediction and experimental results was achieved. The studies in this paper provide a reliable means to predict the blast load in confined space. [ABSTRACT FROM AUTHOR]

Underwater explosion process mainly includes the preceding blast wave and the succeeding bubble pulsation, while the effect of bubble pulsation on hydraulic structures is always neglected. This paper aims to numerically study the dynamic behaviors of prototype concrete gravity dam against underwater explosion, considering the combined effects of blast wave and bubble pulsation. Firstly, a finite element analysis (FEA) approach for predicting the underwater explosion loadings, as well as the damage evolution and dynamic responses of dam against underwater explosions was proposed, in which the hydrostatic pressure of reservoir and the dead load of dam were considered. Based on Cole's formula and the existing underwater explosion tests, the reliability of FEA approach, including the mesh sizes, material models and the corresponding parameters, as well as the mapping, Fluid-Structure Interaction and contact algorithms, was comprehensively validated. Secondly, to realize the simulation of the prototype gravity dam impeded by the validated small Lagrange mesh size, a mesh transition strategy was proposed based on the equivalence of dam damage modes and total eroded element mass. Finally, the dynamic behaviors of a typical 120 m-height concrete gravity dam against underwater explosion, i.e., 1 t of TNT equivalence detonated at a depth of 35 m and standoff distances of 4–16 m, were examined. The dimensionless distance λ R , i.e., the ratio of the standoff distance to the maximum bubble radius, was introduced to quantitatively evaluate the underwater explosion loadings and dynamic behaviors of the dam. It indicates that, the blast wave firstly leads to the local compressive damage on the upstream surface, as well as the tensile damage on the downstream folded slope and dam heel. The succeeding free vibration and bubble pulsation will further aggravate the damage degree, resulting in the cracking of dam neck and heel. Especially for the scenarios when λ R ≤ 1.22, the overall sliding of dam is highly prone to occur. • FEA approach for hydraulic structures against underwater explosions is proposed. • Accurate simulation for prototype dam is realized using mesh transition strategy. • Dynamic behaviors of dam against combined blast wave and bubble pulsation are studied. • Effect of standoff distance on blast resistance of concrete gravity dam is discussed. [ABSTRACT FROM AUTHOR]

• Blast wave propagation from mine entrances investigated with Advanced Blast Simulator. • Mine entrance variants studied: portal with highwall, standalone portal, and shaft. • Blast overpressure vs. radial distances of different mine entrances established. • Blast hazards are identified for mine entrances of different types, shape, and dimensions. • Blast attenuation faster with vertical shafts than horizontal portals along surface. Although there is a wealth of information on the emission of gas and explosions due to methane-air and/or coal dust in mines underground, the underlying threats on the surface from the explosive energy transmitted through the mine entrances have been largely overlooked. These hazards have the potential to cause injuries and loss of life. Additionally, they can lead to severe damage to the surface infrastructure surrounding the mine entrance. This study aims to establish the relationship between characteristics of blast waves emanating from the mine entries for different magnitudes of explosions and radial distances. An Advanced Blast Simulator (shock tube) was used to experimentally study the propagation of blast waves from mine entrances and over an outside mine site terrain (for mine portals) or upwards towards the sky (for mine shafts). Computational Fluid Dynamics modelling was utilised to interpret the experimental data, verify the applicability and scalability of the small-scale experimental data for actual (large) scale problems, and provide more data points for the creation of blast overpressure contours with enhanced resolution. The paper concludes with several worked examples with detailed steps and commentary for characterising explosion risk around entrances of coal mines using the results derived from the present study. [ABSTRACT FROM AUTHOR]

• A blast modeling strategy for protective tunnel with expansion chamber was provided. • Found significant mitigation improvements with optimized chamber designs. • Chamber's length-to-width ratio greater than 1.5 led to effective blast mitigation. • Impact of blast wave diffraction emphasizes the need for proper chamber dimensions. • Maximum overpressure reduction by chamber was 66%, and 73% for impulse. This paper presents a numerical investigation into the effect of expansion chamber in mitigating overpressures and impulses in protective tunnels subjected to detonation of high explosives. Blast shockwave propagation in a protective tunnel, with dimensions of 160 m in length, 8.9 m in width and 7.2 m in height, was simulated using a computational fluid dynamics code, Viper::Blast. The design parameters of the expansion chamber cover a broad spectrum chamber lengths between 6.1 and 12.1 m, widths spanning from 10.7 to 97 m, length-to-width ratios from 0.0 (indicating no chamber) to 5.0, heights of 8.0 and 14.9 m, and chamber-to-tunnel width ratios in the range of 1.2 to 10.9 m. Two charge weights of 1000 and 2000 kg of TNT were employed to assess their influences. To ensure the reliability of the CFD model, mesh sensitivity analysis, overpressure stability assessments, and validation studies were undertaken. A parametric analysis was then conducted using the validated model to derive an optimal design for the expansion chamber within the specified tunnel. Recommendations for incorporating an expansion chamber into protective tunnels under blast events are provided. [ABSTRACT FROM AUTHOR]

The estimation of wave transmission across the fractured rock masses is of great importance for rock engineers to assess the stability of rock slopes in open pit mines. Presence of fault, as a major discontinuity, in the jointed rock mass can significantly impact on the peak particle velocity and transmission of blast waves, particularly where a fault contains a thick infilling with weak mechanical properties. This paper aims to study the effect of fault properties on transmission of blasting waves using the distinct element method. First, a validation study was carried out on the wave transmission across a single joint and different rock mediums through undertaking a comparative study against analytical models. Then, the transmission of blast wave across a fault with thick infilling in the Golgohar iron mine, Iran, was numerically studied, and the results were compared with the field measurements. The blast wave was numerically simulated using a hybrid finite element and finite difference code which then the outcome was used as the input for the distinct element method analysis. The measured uplift of hanging wall, as a result of wave transmission across the fault, in the numerical model agrees well with the recorded field measurement. Finally, the validated numerical model was used to study the effect of fault properties on wave transmission. It was found that the fault inclination angle is the most effective parameter on the peak particle velocity and uplift. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Rudarsko-Geolosko-Naftni Zbornik is the property of Faculty of Mining, Geology & Petroleum Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Safety is one of the goals of a smart city. To study storage tank explosion damage in a city's chemical industrial parks, determine the position of control measures according to the situation, and realize the analysis of the measured utility, we proposed the area damage probability importance distribution. In this way, the prediction and prevention of risk in chemical industrial parks can be achieved intelligently. The concept of area damage probability importance distribution was given, and the utility analysis method of the control measures for storage tank explosion accidents was put forward. It is concluded that the area damage probability importance distribution represents the change degree of damage probability: that is, the damage degree of storage tank explosion in a chemical industrial park. The control measures for a storage tank explosion can be set up in varying positions, as the explosion damage is mainly caused by shock waves; the blast walls are selected as the measure set, and the calculation method for the area damage probability is modified. By comparing the calculated area damage probability distribution before and after, evaluation of the control measures' effectiveness can be achieved. Finally, the flow chart of the algorithm is given. The example analysis shows that the calculation process and analysis results meet the design requirements of the algorithm. The effectiveness of the method, the distribution characteristics, and the significance and function of the importance distribution of damage probability are discussed. This provides an effective method for smart cities to predict and prevent the impact of an explosion at chemical industrial parks. [ABSTRACT FROM AUTHOR]

We investigate the transverse momentum spectra of identified particles at 7 and 13 TeV in pp collisions in the framework of the blast wave model with Tsallis statistics (TBW). Based on experimental data by ALICE Collaboration, we observe that the model describes the p T spectra well with the common Tsallis temperature (T) and flow velocity (β T ) but separate non-extensive parameters (q) for baryons and mesons. The parameter dependence on multiplicity as well as on collision energy is investigated, and a strong dependence on the former while a weak dependence on the latter is reported. The extracted parameters in this work consist of the initial temperature (T i ), the average transverse momentum (〈 p T 〉), the Tsallis temperature (T), the flow velocity (β T ), and the non-extensive parameter (q). These parameters are found to increase a little with increasing energy, however, they (except the parameter q) decrease significantly with decreasing multiplicity. We observe that β T drops to zero at high multiplicity, while, T and q do not change their behavior. Furthermore, our analysis explore the correlations among different parameters, including associations with the charged particle multiplicity per unit pseudorapidity ( 〈 d N ch / d η 〉 ). The correlations between T and β T , T and 〈 d N ch / d η 〉 , β T and 〈 d N ch / d η 〉 , T i and 〈 p T 〉 and T i and 〈 d N ch / d η 〉 demonstrates a positive relationship, while, the correlation between T and q − 1, and q − 1 and 〈 d N ch / d η 〉 is negative. Finally, we implement an extra flow correction on the T parameter. Our findings reveal that the Doppler-corrected temperature parameter aligns closely with the T in scenarios with lower multiplicities. However, as the multiplicity increases, a noticeable divergence emerges between these parameters, indicating a widening separation between them. [ABSTRACT FROM AUTHOR]

Foam concrete is a prospective material in defense engineering to protect structures due to its high energy absorption capability resulted from the long plateau stage. However, stress enhancement rather than stress mitigation may happen when foam concrete is used as sacrificial claddings placed in the path of an incoming blast load. To investigate this interesting phenomenon, a one-dimensional difference model for blast wave propagation in foam concrete is firstly proposed and numerically solved by improving the second-order Godunov method. The difference model and numerical algorithm are validated against experimental results including both the stress mitigation and the stress enhancement. The difference model is then used to numerically analyze the blast wave propagation and deformation of material in which the effects of blast loads, stressestrain relation and length of foam concrete are considered. In particular, the concept of minimum thickness of foam concrete to avoid stress enhancement is proposed. Finally, non-dimensional analysis on the minimum thickness is conducted and an empirical formula is proposed by curve-fitting the numerical data, which can provide a reference for the application of foam concrete in defense engineering. [ABSTRACT FROM AUTHOR]

The Beirut port explosion on August 4, 2020, caused extensive destruction and significant casualties, prompting inquiries into its scale and impact on neighboring structures. Speculation arose regarding the role of the nearby port silos in shielding western Beirut from the blast. This study leverages insights from previous research and uses a tailored blast wave propagation model to settle the debate on the silos' effectiveness in mitigating blast impacts. The analysis challenges prevailing notions: firstly, that the silos offered substantial protection, and secondly, the assumption linking the transient "window" phenomenon in the Wilson cloud to a similar opening in the preceding pressure front. Contrary to expectation, the pressure at the shock front remains continuous, albeit lower on the leeward side behind the silos. Downstream lateral regions experience pressure amplification due to the constructive interference of waves diffracted around the silos, with significant attenuation observed close (10 m) behind them—approximately 12%, 58%, and 2% of free-air values for overpressure, specific impulse, and specific energy, respectively. However, this shielding effect diminishes with distance, with the blast wave intensity largely restored at 450 m. Consequently, the silos' shadowing effect was limited to nearby port structures and part of the Lebanese navy base, which still incurred severe damage. The lesser impact on western Beirut is attributed to its greater distance from the explosion rather than the silos' protective influence. These findings suggest a reevaluation of urban disaster mitigation strategies, emphasizing geographical positioning over structural barriers and advocating for a holistic approach to urban resilience. [ABSTRACT FROM AUTHOR]

Based on our Chandra imaging-spectroscopic observations, we present the latest evolution of the X-ray remnant of SN 1987A. Recent changes in the electron temperatures and volume emission measures suggest that the blast wave in SN 1987A is moving out of the dense inner ring structure, also called the equatorial ring (ER). The 0.5–2.0 keV X-ray light curve shows a linearly declining trend (by ∼4.5% yr−1) between 2016 and 2020 as the blast wave heats the hitherto unknown circumstellar medium (CSM) outside the ER. While the peak X-ray emission in the latest 0.3–8.0 keV image is still within the ER, the radial expansion rate in the 3.0–8.0 keV images suggests an increasing contribution of the X-ray emission from less dense CSM since 2012, at least partly from beyond the ER. It is remarkable that, since 2020, the declining soft X-ray flux has stabilized around ∼7 × 10−12 erg s−1 cm−2, which may signal a contribution from the reverse-shocked outer layers of ejecta as predicted by the three-dimensional magnetohydrodynamic models. In the latest ACIS spectrum of supernova remnant 1987A in 2022 we report a significant detection of the Fe K line at ∼6.7 keV, which may be due to changing thermal conditions of the X-ray emitting CSM and/or the onset of reverse shock interactions with the Fe ejecta. [ABSTRACT FROM AUTHOR]

Adjacent cyclic explosions significantly impact the stability of underground anchored caverns. Based on the similar model test of the vault explosion of the anchored cavern, the dynamic analysis finite element software ANSYS/LSDYNA(18.0) was used to establish a model of the straight wall side explosion of the underground anchored cavern and conduct a numerical simulation. When the total amount of explosion load is the same, we compared the stress time history curve, displacement time history curve, tunnel wall displacement, and circumferential strain curve of the surrounding rock in the underground anchored cavern (under both a high-level single-side blast and a low-level cyclic side blast). We obtained the dynamic response rules of the surrounding rock. By comparing the damage evolution process of the surrounding rock in the two situations, the damage accumulation law of the surrounding rock was analyzed. At the same time, the axial stress distribution characteristics of underground anchor cavern anchors under the action of cyclic explosion were studied. The findings demonstrate that when the total level of blast load adjacent to the cavern is the same, the displacement and circumferential peak strain of surrounding rock and the axial stress of rock bolt in the high-level single explosion are greater than those in the low-level cyclic explosion. However, compared to a single explosion, the rock mass suffers more damage in the cyclic explosion. This study will provide engineers with information that will assist them with a better understanding of the cumulative damage mechanisms of surrounding rock, as well as the stress characteristics of rock bolts under dynamic loads near the explosion site, which will be used to design underground caves with anti-blast features. [ABSTRACT FROM AUTHOR]

It is important to study the effect of ambient pressure on air blasts, and the explosion process of TNT explosives was calculated by using the AutoDyn-2D software in this paper. Moreover, the explosion parameters under different ambient pressure conditions were predicted, and the propagation characteristics and laws of the air blast waves were obtained. The results showed that the overpressure of the incident wave, reflected wave, and Mach wave was positively related to the ambient pressure. High ambient pressure resulted in a decrease in the barotropic time and velocity of the incident wave, but its impulse increased. The wavefront of the Mach wave propagated in a curved form, and the pressure distribution on the Mach stem was not uniform. The height of the triple points was inversely proportional to the increase in the ambient pressure, and this trend was significant with the increase in the distance. [ABSTRACT FROM AUTHOR]

Most of the damage caused by an explosion is caused by a pressure effect. The magnitude of the pressure generated by the explosion is influenced by the external characteristics of the environment (surrounding objects, their arrangement, geometry, etc.) and internal characteristics (type of explosive, type of charge, booster and others). An effective combination of internal factors creates a symmetry that results in the highest possible value of pressure generated by the charge explosion. The paper focuses on the influence of the booster reaction on this symmetry. The scope of the paper is to understand the dependency of the blast wave pressure on the amount of used blaster to increase the efficacy of explosions on the environment and structures to increase the protection of affected structures. The open-air field tests were conducted using different types of explosives: trinitrotoluene and three different types of industrially made ANFO explosives (pure ammonium nitrate and fuel oil, ammonium nitrate and fuel oil plus aluminum powder, ammonium nitrate and fuel oil mixed with trinitrotoluene). The obtained data were compared with the analytical approach for setting the generated maximal pressure on the front of the blast wave. [ABSTRACT FROM AUTHOR]

A Cartesian grid-based sharp interface method is presented for viscous simulations of shocked particle-laden flows. The moving solid–fluid interfaces are represented using level sets. A moving least-squares reconstruction is developed to apply the no-slip boundary condition at solid–fluid interfaces and to supply viscous stresses to the fluid. The algorithms developed in this paper are benchmarked against similarity solutions for the boundary layer over a fixed flat plate and against numerical solutions for moving interface problems such as shock-induced lift-off of a cylinder in a channel. The framework is extended to 3D and applied to calculate low Reynolds number steady supersonic flow over a sphere. Viscous simulation of the interaction of a particle cloud with an incident planar shock is demonstrated; the average drag on the particles and the vorticity field in the cloud are compared to the inviscid case to elucidate the effects of viscosity on momentum transfer between the particle and fluid phases. The methods developed will be useful for obtaining accurate momentum and heat transfer closure models for macro-scale shocked particulate flow applications such as blast waves and dust explosions. [ABSTRACT FROM PUBLISHER]

An experimental test facility has been developed for performing laboratory studies on shallow buried blast loading. The shock tube based test facility offers an alternative method for generating blast wave in a controlled and repeatable manner, without the use of explosives. In this paper, we consider a spherical expanding blast wave of moderate shock strength with relatively low driving pressure. A confined dry sand bed prepared with a constant density, is exposed to a blast wave from the embedded shock tube. The principal objective of this paper is to understand the various events involved during the interaction of leading blast wave with the soil medium, followed by the expansion of the entrained gas. The process initiates with the formation of stress wave in the sand media, followed by the gas bubble expansion and terminates with sand ejection. The variation in the output of the sand ejecta is investigated with the help of high speed photography. The velocity of the sand ejecta front is found to decrease with the increase in the burial depth (DoB). Further, the impulse (using vertical pendulum) and peak pressure (using transducers) imparted to the rigid target are evaluated. The target is located at different stand-off distances (SoD) above the top surface of the sand bed. It is found that the peak pressure values are influenced by the presence of dome-cap of the ejecta, expanding vertically upwards generating a point-load impact. Irrespective of the depth of burial (DoB = 32 mm–64 mm), maximum impulse is observed around the zone of bubble expansion (close to the sand bed surface). Sand ejecta does however have a greater influence on the impulse at higher SoDs (> 40 mm). Moreover, the maximum momentum transfer is observed when SoD to DoB ratio is 2.5. In conclusion, the shock-driven sand test facility is found to be a simple and efficient tool to study the complex dynamics of sand ejecta, including the post- impact on the target structures. [ABSTRACT FROM AUTHOR]

This paper concerns the propagation of shock waves in an enclosure filled with dusty gas. The main motivation for this problem is to probe the effect on such dynamics of solid particles dispersed in the fluid medium. This subject, which has attracted so much attention over recent years given its important implications in the study of the structural stability of systems exposed to high-energy internal detonations, is approached here in the framework of a hybrid numerical two-way coupled Eulerian-Lagrangian methodology. In particular, insights are sought by considering a relatively simple archetypal setting corresponding to a shock wave originating from a small spherical region initialized on the basis of available analytic solutions. The response of the system is explored numerically with respect to several parameters, including the blast intensity (via the related value of the initial shock Mach number), the solid mass fraction (mass load), and the particle size (Stokes number). Results are presented in terms of pressure-load diagrams. Beyond practical applications, it is shown that a kaleidoscope of fascinating patterns is produced by the "triadic" relationships among multiple shock reflection events and particle-fluid and particle-wall interaction dynamics. These would be of great interest to researchers and scientists interested in fundamental problems relating to the general theory of pattern formation in complex nonlinear multiphase systems. [ABSTRACT FROM AUTHOR]

Blast-induced traumatic brain injury (bTBI) is a rising health concern of soldiers deployed in modern-day military conflicts. For bTBI, blast wave loading is a cause, and damage incurred to brain tissue is the effect. There are several proposed mechanisms for the bTBI, such as direct cranial entry, skull flexure, thoracic compression, blast-induced acceleration, and cavitation that are not mutually exclusive. So the cause-effect relationship is not straightforward. The efficiency of protective headgears against blast waves is relatively unknown as compared with other threats. Proper knowledge about standard problem space, underlying mechanisms, blast reconstruction techniques, and biomechanical models are essential for protective headgear design and evaluation. Various researchers from cross disciplines analyze bTBI from different perspectives. From the biomedical perspective, the physiological response, neuropathology, injury scales, and even the molecular level and cellular level changes incurred during injury are essential. From a combat protective gear designer perspective, the spatial and temporal variation of mechanical correlates of brain injury such as surface overpressure, acceleration, tissue-level stresses, and strains are essential. This paper outlines the key inferences from bTBI studies that are essential in the protective headgear design context. [ABSTRACT FROM AUTHOR]

The initial stresses have a strong effect on the mechanical behavior of underground rock masses, and the initial stressed rock masses are usually under strong dynamic disturbances such as blasting and earthquakes. The influence mechanism of a blasting excavation on underground rock masses can be revealed by studying the propagation of stress waves in them. In this paper, the improved Mohr-Coulomb elasto-plastic constitutive model of the intact rock considering the initial damage was first established and numerically implemented in Universal Distinct Element Code (UDEC) based on the variation of the experimental stress wave velocity in the initial stressed intact rock, and the feasibility of combining the established rock constitutive model and the BB (Bandis-Barton) model which characterizes the nonlinear deformation of the joints to simulate stress waves across jointed rock masses under initial stress was validated by comparing the numerical and model test results subsequently. Finally, further parameter studies were carried out through the UDEC to investigate the effect of the initial stress, angle, and number of joints on the transmission of the blasting stress wave in the jointed rock mass. The results showed that the initial stress significantly changed the propagation of the stress waves in the jointed rock mass. When the initial stress was small, the transmission coefficients of the stress waves in the jointed rock were vulnerable to be influenced by the variation of the angle and the number of joints, while the effect of the angle and the number of joints on the stress wave propagation gradually weakened as the initial stress increased. [ABSTRACT FROM AUTHOR]

Despite the greatest efforts, accidents continue to happen during the process of rocket launching, either in the form of generated blast wave or the debris that flies and hits random objects. In this paper, the impact of blast loading created by a rocket launch on the tie connection and the threehinged arch is studied using the finite element model in ABAQUS. The impact of rocket launching was modelled using the physical characteristics/geometry of the launch pad, and a blast load intensity equivalent to 20,000lbs of TNT is applied using the CONWEP module. The tie connection and threehinged arch after validation and mesh convergence study are applied with service loads in concurrence with the blast loading. The additional impact of blast loads on the static and dynamic response of the structure is studied. The distance of the structures from the point of blast (rocket launching site) is varied, and parametric studies are carried out to arrive at detailed guidelines on the minimum safety distance that stand-alone civil infrastructure should follow in order to minimize the rocket launching impact. [ABSTRACT FROM AUTHOR]

• Appropriate injury loading conditions are needed for meaningful research outcomes. • There lacks consensus in the application and assumptions of PBI predictive criteria. • Existing PBI criteria can define zones of clinically-relevant blast wave parameters. • Application of PBI criteria could support clinical response to explosion incidents. • Further work is needed to define blast exposure thresholds for mild blast TBI. Blast injuries remain a serious threat to defence and civilian populations around the world. 'Primary' blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting air-containing organs. Work to define blast loading conditions for injury research has received relatively little attention, though with a continued experimental focus on PBIs and idealised explosion assumptions, meaningful test outcomes and subsequent clinical applications, rely on appropriate simulated conditions. This paper critically evaluates and combines existing PBI criteria (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) as a function of idealised blast wave parameters. For clinical blast injury researchers, analysis of the multi-injury criteria indicates zones of appropriate loading conditions for human-scale test items and demonstrates the importance of simulating blast conditions that are both realistic and relevant to the injury type. For certain explosive scenarios, spatial interpretation of the 'zones of relevance' could support emergency response and hazard preparedness by informing triage, patient management and resource allocation, thus leading to improved health outcomes. This work will prove useful to clinical blast injury researchers, blast protection engineers and clinical practitioners involved in the triage, diagnosis, and treatment of PBIs. [ABSTRACT FROM AUTHOR]

We demonstrate that the geometric similarity of Taylor's blast wave persists beyond reflection from an ideal surface. Upon impacting the surface, the spherical symmetry of the blast wave is lost but its cylindrical symmetry endures. As the flow acquires dependence on a second spatial dimension, an analytic solution of the Euler equations becomes elusive. However, the preservation of axisymmetry, geometric similarity and planar symmetry in the presence of a mirror-like surface causes all flow solutions to collapse when scaled by the height of burst (HOB) and the shock arrival time at the surface. The scaled blast volume for any yield, HOB and ambient air density follows a single universal trajectory for all scaled time, both before and after reflection. [ABSTRACT FROM AUTHOR]

• This article elucidates the energy exchange mechanism between blast loading and energy absorbing structures through the proposed theoretical analysis model. • Energy exchange efficiency (EEE) is positively corrected with the peak overpressure and specific impulse of reflected wave, as it enhances the reflection coefficient. • Increasing areal density of ETS enhances impulse transfer while impending energy exchange with the blast wave. • Effective impulse of reflected wave is inversely corrected with equivalent strength of ETS, leading to a reduction in EEE by increasing equivalent strength. The mechanical response and energy absorption characteristics of the energy-absorbing structure under blast loading are widely concerned in engineering protection, while the energy exchange mechanism remains poorly understood, thereby limiting improvements in energy absorption performance under blast loading. This paper utilizes the expansion tube structure (ETS) as a typical energy-absorbing structure to investigate the energy exchange mechanism under blast loading. Following an experimental verification, numerical simulations are conducted to investigate the effect of relevant parameters on the energy exchange characteristics. A theoretical model based on the strong-shock hypothesis is developed and validated against numerical results to predict the energy absorption efficiency of ETS under blast loading. The findings reveal that increasing the areal density of ETS positively impacts impulse transfer, but does not contribute significantly to energy exchange between the blast wave and ETS. Notably, there exists a significant negative correlation between the energy exchange efficiency and areal density. An approximately linear positive correlation is observed between the energy exchange efficiency and both peak overpressure and specific impulse of the reflected wave due to an enhanced reflection coefficient of the blast wave. Moreover, increasing equivalent strength leads to a decrease in energy exchange efficiency as it negatively correlates with effective impulse of the reflected wave. This study elucidates the underlying mechanisms governing energy exchange in expansion tube under blast loading, providing valuable insights for optimizing designs of energy-absorbing structures. [Display omitted] [ABSTRACT FROM AUTHOR]

• Energy absorption per unit area (EAUA) of expansion tube structure (ETS) exhibits a quadratic correlation with the explosive mass/(standoff distance)2. • EAUA is linear correlated with the reciprocal of areal density of the ETS. • The effect of equivalent strength of the ETS on EAUA is relatively insignificant. • The proposed explosion power model demonstrates a remarkable degree of precision in estimating explosive mass with errors within ±15 %. With the rapid advancement of the new generation of ammunition, the evaluation of the explosion power has received worldwide attention. To assess the power of blast waves generated by explosives, an explosion power evaluation method, based on analyzing the energy absorption characteristics of an expansion tube structure (ETS), is proposed in this paper. Explosion experiments and numerical simulations are carried out to investigate the energy absorption characteristics of the ETS under blast loading, and a verified theoretical model is developed to predict the energy absorption per unit area (EAUA) of the ETS. The parametric studies demonstrate a quadratic positive correlation between the EAUA of ETS and the explosive mass/(standoff distance)2, as well as a linear correlation with the reciprocal of areal density of the ETS. However, the effect of equivalent strength of the ETS on the EAUA is less significant. Furthermore, an explosion power model is established using dimensional analysis. The evaluation errors of this model in estimating explosive mass are -11.34 % to 14.67 % when compared with the actual mass of the explosive trinitrotoluene (TNT), and it also shows errors of -13.94 % to 0.97 % when compared with the explosive mass estimated through free field overpressure sensors, which all fall within the range of ±15 %, demonstrating that the proposed method meets the accuracy requirements for explosion power evaluation. This research provides a novel and accurate methodology for evaluating the power of ammunition in explosion field, especially for testing in extreme conditions. [ABSTRACT FROM AUTHOR]

• This paper uses numerical simulations and comparative experiments to obtain the human somatosensory shock wave pressure (SSWP, the real perceived pressure of the human tissue when the shock wave overpressure acts on the human body.) signals output by Poly-vinylidene fluoride (PVDF) film and piezoelectric pressure sensor under the same shock wave load, and conducts comparative analysis. The analysis results show that the measurement results of PVDF film are closer to SSWP. • Under the same shock wave load, the pressure response of PVDF film and human tissue has extreme similarity, which is significantly better than the traditional piezoelectric pressure sensor. The smaller the thickness of the PVDF film, the closer the pressure response to human tissue. The matching degree is as high as 98.8 % when the thickness of PVDF film is 20 μm. • According to the comparison experiment, the somatosensory shock wave measured value of PVDF film is more stable than the piezoelectric pressure sensor under the same shock wave input load. Piezoelectric pressure sensors and human tissue have different pressure impedance coefficients, which results in a discrepancy when accurately measuring the real somatosensory shock wave pressure (SSWP). The aim of this research is to develop a method that can realistically characterize SSWP measurements. To achieve this, the study uses the finite element method to analyze the response of both human tissue and piezoelectric pressure sensors to the same shock wave load. The numerical simulation results show a significant difference in the pressure response between the two under identical shock wave loads. Based on this, the working mode and equivalent model of Polyvinylidene fluoride (PVDF) film for measuring SSWP are determined. Using the finite element method, the same shock wave pressure load is applied to PVDF films with thicknesses of 20 μm, 50 μm, 100 μm, as well as human tissue. The results reveal a good agreement between the pressure response of the PVDF film and human tissue. As the thickness of the PVDF film decreases, particularly at 20 μm thickness, the accuracy improves. Additionally, a comparative experiment is conducted using a bionic dummy model. The outcomes indicate that PVDF film is more stable than piezoelectric pressure sensors and can accurately characterize the real SSWP, aligning with the numerical simulation results by up to 98.4%. [ABSTRACT FROM AUTHOR]

• FBG sensor is introduced for measuring blast wave induced dynamic strain in polymer materials. • FBG sensor usage in Vertical Shock Tube (VST) is demonstrated for the first time. • Experiments are conducted by impacting the polymer materials with blast waves of different peak pressures. • The FBG strain signals are studied using time–frequency analysis. • FEM analysis of dynamic strain response of the two polymer samples is carried out. Polypropylene and polytetrafluoroethylene (Teflon) have several applications in the aerospace industry and the study of their behaviour in high speed impact events is of great significance. This paper demonstrates the use of FBG sensors for measuring blast wave induced strain in aerospace grade polymer samples inside a Vertical Shock Tube (VST). FBG strain measurement assembly incorporating the polymer test sample and embedded FBG sensor has been designed and developed for suitably mounting it in the driven section of the VST. Experiments are carried out by impacting the polymer samples with blast waves of different peak pressures generated inside VST. PCB pressure transducer is used to record the blast pressure profile in the VST. A systematic study of strain profiles developed in the polymer test samples and their dependence on incident blast wave parameters has been carried out. The strain profiles measured by FBG in both the polymer samples are analysed using FFT and continuous wavelet transform analyses. FEM analysis is carried out using ABAQUS dynamic explicit to simulate the blast wave induced compression in polymers for different blast wave peak pressures and compared with experimental results. The application of FBG sensors to measure blast wave induced dynamic strain inside polymer materials and their capability to withstand the harsh environment of impulse test facilities like shock tubes has been demonstrated. [ABSTRACT FROM AUTHOR]

Heterotopic ossification (HO) is a consequence of traumatic bone and tissue damage, which occurs in 65% of military casualties with blast-associated amputations. However, the mechanisms behind blast-induced HO remain unclear. Animal models are used to study blast-induced HO, but developing such models is challenging, particularly in how to use a pure blast wave (primary blast) to induce limb fracture that then requires an amputation. Several studies, including our recent study, have developed platforms to induce limb fractures in rats with blast loading or a mixture of blast and impact loading. However, these models are limited by the survivability of the animal and repeatability of the model. In this study, we developed an improved platform, aiming to improve the animal's survivability and injury repeatability as well as focusing on primary blast only. The platform exposed only one limb of the rat to a blast wave while providing proper protection to the rest of the rat's body. We obtained very consistent fracture outcome in the tibia (location and pattern) in cadaveric rats with a large range of size and weight. Importantly, the rats did not obviously move during the test, where movement is a potential cause of uncontrolled injury. We further conducted parametric studies by varying the features of the design of the platform. These factors, such as how the limb is fixed and how the cavity through which the limb is placed is sealed, significantly affect the resulting injury. This platform and test setups enable well-controlled limb fracture induced directly by pure blast wave, which is the fundamental step towards a complete in vivo animal model for blast-induced HO induced by primary blast alone, excluding secondary and tertiary blast injury. In addition, the platform design and the findings presented here, particularly regarding the proper protection of the animal, have implications for future studies investigating localized blast injuries, such as blast induced brain and lung injuries. [ABSTRACT FROM AUTHOR]