Blast Wave Propagation Research Articles

Statistical analyse of outdoor blast wave propagation in real environments

The propagation of outdoor blast waves is governed by numerous physical parameters, including source energy, terrain relief, ground nature, and atmospheric conditions. Among these, certain effects are deterministic and can be effectively modeled through numerical simulations. This research leverages the one-way Flhoward code, used with Arome meteorological data and IGN topography, to simulate the waveforms of blast waves originating from 300 kg explosions up to a distance of 20 km. Given the inherent randomness of the medium, these waveform signatures exhibit a high degree of uncertainty. To address this uncertainty, we introduce a metamodel based on polynomial chaos, designed to quantify the uncertainties. First, this study focuses on the validation of the code for accurately simulating waves above a relief. Subsequent steps of the study involve a comprehensive comparison of outcomes from direct simulations and metamodel-based simulations against measurements obtained from records of well-calibrated ground explosions. This comparison not only validates the effectiveness of the Flhoward code and the developed metamodel but also highlights the significance of considering the random nature of the medium. This research paves the way to a framework for understanding and anticipating the impact of such phenomena across varied outdoor environments.

Probabilistic analysis of near-field blast loads considering fireball surface instabilities and stochastic detonator location

High speed video analysis of near-field explosive detonations displays distinct stages of emergent hydrodynamic instabilities in the fireball/shock-air interface. Typically, beyond 10 charge radii, the instabilities experienced large growths giving rise to more chaotic behaviour of the interface and thus an increasing uncertainty in surface velocity. These surface instabilities are suggested as the primary cause of blast parameter variability in the near-field. However, as a deterministic tool, numerical simulation of the detonation process and subsequent blast wave propagation is not able to replicate the stochastic nature of fireball surface instabilities and hence near-field blast parameter variability. Therefore, it is necessary to develop new methods to simulate and characterise the stochastic features of the fireball/shock-air interface. This paper proposes an algorithm to generate an explosive charge element with random shape in finite element model in order to simulate irregularities in the fireball/shock-air interface, and therefore produce variabilities comparable to those from direct observation. The effect of chaotic fireball/shock-air interface on near-field loading is explored through a large number of numerical simulations in order to investigate the statistical distribution of parameters including peak overpressure and impulse. Subsequently, the effect of stochastic detonator location is explored in a similar manner. A computational procedure based on the Monte Carlo Method is proposed to establish a probabilistic model of near-field blast loads, termed PSL-Blast. The reliability of design blast loads calculated using the UFC 3-340-02 design manual is then estimated using PSL-Blast, which suggests that reliability decreases with decreasing scaled distance. Finally, reliability-based safety factors of blast loads are calculated based on different blast settings.

Approximate analytical solution using power series method for the propagation of blast waves in a rotational axisymmetric non-ideal gas

In this paper, the propagation of the blast (shock) waves in non-ideal gas atmosphere in rotational medium is studied using a power series method in cylindrical geometry. The flow variables are assumed to be varying according to the power law in the undisturbed medium with distance from the axis of symmetry. To obtain the similarity solution, the initial density is considered as constant in the undisturbed medium. Approximate analytical solutions are obtained using Sakurai’s method by extending the power series of the flow variables in power of a0U2, where U and a0 are the shock velocity and speed of sound, respectively, in undisturbed fluid. The strong shock wave is considered for the ratio a0U2 which is considered to be a small quantity. With the aid of that method, the closed-form solutions for the zeroth-order approximation is given as well as first-order approximate solutions are discussed. Also, with the help of graphs behind the blast wave for the zeroth-order, a comparison between the numerical solution and the approximate analytical solution are shown. The distributions of flow variables such as density, radial velocity, pressure and azimuthal velocity are analysed. The results for the rotationally axisymmetric non-ideal gas environment are compared to those for the ideal gas atmosphere. The velocity-distance and time-distance curves are also shown to analyse the decaying characteristic of a blast wave.

Blast wave interaction during explosive detonation in a variable cross-sectional charge

Purpose. The research aims to assess the efficiency and performance of solid media destruction in directed blasting of a charge with variable cross-sectional shape. Methods. Numerical modelling of the blast wave interaction process is performed using the finite element method based on the Euler-Lagrange algorithm. The Johns-Wilkins-Lee equation of state is used to determine the pressure-volume dependences of medium destruction. Assessment of solid medium destruction mechanism during a directed blasting of a charge with variable cross-sectional shape is carried out based on polarization-optical method on models made of optically active material. Findings. Experimental studies of solid medium destruction by the action of directed blasting with a variable cross-section charge made it possible to determine the direction of blast wave propagation and its amplitude in stress wave, influencing the intensity of radial crack network formation in superposition areas, and directed perpendicularly to explosive cavity. At the same time, the average peak pressure in collision zone of two shock waves in centre of spherical cavity is approximately 1.48 and 1.84 times higher than that in weakly blast-loaded areas. It has been found that when two shock waves collide and superimpose on each other, the intensity of their impact increases. Moreover, the shock wave velocity in collision zone is higher than that of the radial shock wave. Originality. It has been determined that the maximum pressure values on the explosive cavity wall at the initiation points sharply increase and then gradually stabilize as the blast stress waves propagate and have an arbitrary distribution pattern. Three areas should be considered: not superimposed, weakly superimposed, and strongly superimposed. At each point of detonation, the pressure on explosive cavity wall will be minimal, while in the charge centre in the spherical insert zone, on the contrary, it will be maximal. In this case, the pressure in the central superposition area is about 2.84 times greater than at the initiation ends, and the nature of distribution changes according to a linear dependence. Practical implications. The performed research findings can serve as a basis for development of effective parameters of resource-saving methods for stripping hard rocks of complex structure in the conditions of ore mines.

Small-scale airblast testing for the assessment of multiple perimeter wall barriers on shock wave propagation

Assessment of the impact of structural systems on blast wave propagation has traditionally been explored using experimental, analytical, and/or numerical methods. Though numerical modeling techniques have grown in popularity because of their lower cost and high accuracy, experimental testing remains necessary for verifying these models. Issues of scale, equipment capacity, and the availability of research funding continue to limit full-scale testing of subassemblies or complete structures under blast loads. In addition, full-scale blast testing can be time-consuming, allowing only a handful of tests to be conducted. Small-scale airblast experiments offer an economic alternative to full-scale testing, in terms of material and labor requirements. Additionally, these small-scale experiments can be performed rapidly with repeatable results. The use of a novel reusable tabletop small-scale airblast experiment framework is presented for repeatable, cost-effective, quick turnaround testing of airblast scenarios. This novel setup also allows for reflective surfaces to be included as part of the investigation of the behavior of the shockwave-interaction with structures. The goal is to understand the behavior of the blast shockwave interacting with multiple barriers and the effect of pressure due to those barriers; therefore, the scaled structure remains rigid in the experimental and numerical analysis. Three different wall configurations were used to investigate how the presence of multiple barriers affects the shockwave and subsequent observed pressures around and behind the barriers. The explosives used were hemispherical and elevated spherical C4 charges. Pressure gauges were used to read pressures in front of, between, and behind the barriers on the tabletop. The airblast effects such as pressure and impulse, from the scaled experiments are presented and compared to the analytical predictions using a hydrocode model. It was found that multiple walls are measurably effective in reducing the pressure shockwave compared to no walls. The use of single and double walls reduced the pressure by 50% and 25%, respectively, compared to having no walls at the same scaled distance. The hydrocode model results were generally in agreement with the experimental data. The results can allow engineers and decision makers to understand the impact that properly distanced multiple barriers can have on protection from blast events.

Energy quantification framework for underwater explosive loading into PVC foam cladded composite plates

This paper presents a novel approach for analyzing the effects of near-field underwater blast loading on composite marine structures. The operational requirements of these structures often expose them to blast or shock loading, which can lead to significant damage. The study focuses on the propagation of spherical blast waves and the subsequent secondary bubble collapse pulse that affects the structure under near-field underwater blast loading events. An analytical framework is developed to calculate the blast energies and structural energies during this complex loading event. The study further investigates the effect of applying a sacrificial cladding made of low-density closed-cell foam to the loading face of a composite panel. Experiments were conducted in a specialized facility to characterize the explosive-driven blast-loading and the subsequent interaction between the shock pressure front and the structure. Dynamic pressure measurements and high-speed imaging were utilized to capture the behavior of the composite panel under these extreme conditions. 3D digital image correlation was employed to analyze strain and deformation of the composite panel, while high-speed side view cameras captured the fluid-structure interaction during the blast and bubble collapse loading event. The results strongly indicate that the collapse of the explosion bubble is the dominant failure source in near-field underwater blast loadings. The analytical quantification of energy further corroborates the significant damaging effects of bubble collapse due to the buildup of after-flow energies during the bubble collapse duration. Furthermore, the inclusion of low-impedance elastic-plastic PVC foam cladding is shown to significantly mitigate the effect of blast loading on the composite structure.

Ground deformation and blast wave propagation in dry sand subjected to buried explosion: A centrifuge modelling study

A series of centrifuge model tests of buried explosions in dry sand were designed and performed to investigate the blast effects in diverse underground explosion (UE) scenarios. The typical ground deformation pattern and blast wave propagation in different types of UE events were modelled. The excavated cratering was observed in shallow-buried excavation explosion tests. Surface collapse and subsidence craters were formed in the partially contained explosion tests, in which the initial ground motion direction turned from upward to downward with the increase of burial depth. The scaling law for centrifuge modelling of blast wave propagation was derived and examined. The critical burial depth for complete coupling of ground shock energy is within the range of 0.4 m/kg1/3 and 0.8 m/kg1/3, and the gravity effect on blast wave propagation can be disregarded under centrifugal accelerations of 62 g and 106 g (g is the Earth's gravity). The elastic blast wave velocity in dry sand was determined in the model test, and it increased with the burial depth. The attenuation laws for peak pressure and peak scaled acceleration in dry sand were calibrated, and the scaling coefficient for peak pressure estimation increased with the medium's acoustic impedance, while the attenuation coefficient showed a contrasting trend.

Blast wave propagation characteristics of moving charge at diminished pressure

The effects of different diminished pressures on moving charge blast wave parameters were investigated by employing the AUTODYN software. Meanwhile, a theoretical calculation model was established to predict the peak overpressure of the moving charge under diminished pressure conditions and was verified by experimental data and numerical simulations. Results indicate that the model can evaluate the blast wave peak overpressure of moving charge at diminished pressure effectively. As the velocity of the moving charge increases, the peak overpressure of the blast wave from the moving charge increases when the azimuth angle is less than 90°, but it decreases when the azimuth angle is greater than 90°. The blast wave peak overpressure of moving charge decreases but the blast wave action range increases as the ambient pressure decreases.

Non-dimensional analysis on blast wave propagation in foam concrete: Minimum thickness to avoid stress enhancement

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, stress–strain 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.

Stars Bisected by Relativistic Blades

We consider the dynamics of an equatorial explosion powered by a millisecond magnetar formed from the core collapse of a massive star. We study whether these outflows—generated by a priori magneto-centrifugally driven, relativistic magnetar winds—might be powerful enough to produce an ultrarelativistic blade (“lamina”) that successfully carves its way through the dense stellar interior. We present high-resolution numerical special-relativistic hydrodynamic simulations of axisymmetric centrifugally driven explosions inside a star and follow the blast wave propagation just after breakout. We estimate the engine requirements to produce ultrarelativistic lamina jets and comment on the physicality of the parameters considered. We find that sufficiently collimated—half-opening angle θ r ≤ 0.°2—laminas successfully break out of a compact progenitor at ultrarelativistic velocities () and extreme isotropic energies (E k,iso ∼ 5 × 1052 erg) within a few percent of the typical spin-down period for a millisecond magnetar. The various phases of these ultrathin outflows, such as collimation shocks, Kelvin–Helmholtz instabilities, and lifetime, are discussed, and we speculate on the observational signatures echoed by this outflow geometry.

Evaluation of blast wave from hydrogen pipeline burst by a coupled fluid-structure-rupture approach

Coupled fluid-structure-rupture model was developed to evaluate the blast field from X65 hydrogen pipeline burst. Johnson-Cook material model was implemented considering the high strain rates of material at crack tips. Internal hydrogen decompression, outer blast wave generation and propagation, and dynamic rupture of pipeline were simulated simultaneously and validated with experiments. Results demonstrated that the crack primarily ran axially at an average speed of about 120 m/s, while the maximum speed was about 200 m/s. Due to the dynamic growth of rupture opening, the outer blast wave experienced a process of first form and then strengthened by subsequent compression waves. This makes the maximum peak overpressure along the jetting direction appears at a certain standoff distance above rupture. The blast overpressures along the jetting direction were compared and discussed with those from traditional CFD method, TNT equivalence method and Baker-Tang blast curves. It was found the effective volume to calculate the burst energy needs to be further studied. Also, new blast curves were required for quick and rational estimation of blast overpressure from hydrogen pipeline burst.

Two-Dimensional Geometrical Shock Dynamics for Blast Wave Propagation and Post-Shock Flow Effects

Geometrical shock dynamics (GSD) is a model capable of efficiently predicting the position, shape, and strength of a shock wave. Compared to the traditional Euler method that solves the inviscid Euler equations, GSD is a reduced-order model derived from the method of characteristics which results in a more computationally efficient approach since it only considers the motion of the shock front instead of the entire flow field. Here, a study of post-shock flow effects in two dimensions has been performed. These post-shock flow effects become increasingly important when modeling blast wave propagation over extended times or distances, i.e., a shock front that decays in speed and that has decaying properties behind it. A comparison between the first-order complete, fully complete and point-source GSD (PGSD) models reveals the importance of preserving an intact post-shock flow term, which is truncated by the original GSD model, in predicting blast motion. Lagrangian simulations were performed for the case of interaction between two cylindrical blast waves and the results were compared to prior experimental work. The results showed an agreement in attenuation of the maximum pressure at the Mach stem, but an overestimation of the Mach stem growth at its early stage was observed using PGSD. To address this issue, another model was developed that combines the PGSD model with shock–shock approximate theory (PGSDSS), but it excessively attenuates Mach stem evolution.

Propagation of the blast wave in the enclosed blast wall structure (EBWS) at a hazardous chemical storage yard—A mechanism study

The storage and transportation of hazardous chemicals is an essential aspect of modern economic activities. The explosion of hazardous chemicals can cause significant damage to surrounding infrastructure and human life, and has become a major public concern. The enclosed blast wall structure (EBWS) is commonly used in open-air storage yards to segregate explosion hazards. However, the understanding of blast wave propagation in an EBWS is limited. In this study, the propagation of blast waves in an EBWS at a hazardous chemical storage yard was analyzed through a combination of scaled field tests and numerical simulations. The study focuses on reflection and diffraction effects in the access passage, which is connected to the opening of the EBWS for transportation purposes. A decoupling technique was proposed to evaluate the contribution of blast waves propagating through the entrance of the access passage and diffracting from above the blast wall separately. Several special wave propagation effects in EBWS were identified, such as leakage pressure and oblique incidence. The blast load experienced in the access passage were compared with current codes and prediction methods. It was found that the commonly adopted assumptions of a semi-infinite blast wall and normal incidence of blast waves underestimates the peak overpressure in the access passage and could not predict the following multiple overpressure peaks. Finally, a calculation procedure based on the TNT equivalent was proposed to predict the overpressure behind the blast wall with a slant angle.

Numerical study of blast wave propagation through granular materials subjected to buried blasts

Blast wave propagation in dry sand subjected to a buried charge is numerically investigated using a charge-sand stratified configuration wherein the mass ratio between sand and charge (M/C) spans over two decades. The detonation of the central charge and the sand dynamics are modeled by the FEM-DEM method. The findings reveal the pressure-profile associated with the blast wave undergoes marked shape transition as the expansion fans catch up with the incident blast wave. The blast propagation and the associated pressure-profiles depend on the coupling between the sand and the detonation products in the central gas pocket which is in turn influenced by a variety of structural parameters. Specifically, as the M/C increases from 21 to 436, the average velocity of the blast wave decreases by 22.2%. Furthermore, a blast compaction model of sand is proposed to account for the coupling effect and justify the influences arising from key-structural parameters.

Determination method of mesh size for numerical simulation of blast load in near-ground detonation

In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.

Acceleration Measurement Analysis on Warhead Penetration/Explosion on Concrete Targets

Blast wave will be generated in concrete when hit by projectiles at a high velocity. Such blast wave will severely threaten structures. The impact acceleration on the structure surface is an instinctive indicator of the propagation of blast wave, since the acceleration is closely linked to the penetration and explosion state of the warhead. This paper conducted acceleration measurement and analysis on the penetration and explosion of penetration warheads on reinforced concrete target. In addition, test results, on-board testing results and numerical results have been compared to analyze the damage process and mechanism of the target, providing basis for warhead design, target design, simulating calculation and damage efficacy evaluation.

Hybrid Multilayer Perceptron Network for Explosion Blast Prediction

For decades, scientists have studied the blast wave profile produced by an explosive detonation. Based on a significant amount of experimental data, the blast wave propagation profile has been predicted under given parameters. However, most studies have only looked at the central point of initiation for spherical form explosives. The purpose of this research is to compare the prediction performance of blast peak overpressure based on type of explosive, shape of explosive and point of detonation. The blast profiles of Emulex and PE-4, as well as to develop a prediction model using a Hybrid Multilayer Perceptron (HMLP) network. This experiment, which began at a distance of 1.2 m from the ground, employed a total of 500 grams of military explosive and Emulex. At distances of 0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m, 3.0 m, 3.5 m and 4.0 m, the bomb was exploded. The Bayesian Regularization (BR) training algorithm is the best training algorithm for modelling Explosive Blast Prediction.

Blast reliability assessment and sensitivity analysis of steel MRFs equipped with NiTi SMA bolts

The probabilistic-based assessment of Moment Resisting Frame structure (MRFs) is significantly vital due to the high volatility of blast wave propagation parameters, material strength, and strain rate effect. In this study, the reliability and sensitivity of steel MRFs equipped with Nickel Titanium Shape Memory Alloy (NiTi SMA), and smart MRFs, subjected to Vehicle Borne Improvised Explosive Device (VBIED) are assessed. Since Eurocode does not address the design of a smart structure subjected to blast loading, the smart MRFs are designed based on the Eurocode-complying key design procedures proposed by the author’s previous works. It is always a question if the structure designed based on the proposed Eurocode-complying design methodology satisfies the safety level criteria. The newly developed reliability framework approach by the authors is employed to assess the safety level of the smart MRFs based on the criteria given in the international probabilistic design provisions. Performance functions are parameterized based on three failure modes: axial force and bending moments (global buckling) in the columns, maximum rotation demand at the connections, and system-level structural integrity through Inter-Story Drift Ratio (ISDR). The uncertainties of the charge weight, material strength, gravity loads, model uncertainties, connection behavior parameters, strain rate effects, and column cross-sectional dimensions are considered. The proposed reliability framework is applied to the 4-story, 7-story, 10-story, and 15-story smart MRFs. The results show that the developed smart MRFs satisfy the safety level criteria recommended in the international provisions’ probabilistic design requirement. Furthermore, the reliability-based outcome confirms the efficiency and applicability of the proposed Eurocode complying key design procedures and verifies the deterministic results of the smart MRFs. Finally, the sensitivity of the smart structures to various uncertain parameters is investigated. Among all the parameters, it is found that the Reliability Index (β) of the smart MRFs is more sensitive to the uncertainties of charge weight, column web length(s), connection behavior parameters, and material strength. The sensitivity analysis shows that the smart MRFs are safe under unknown extreme conditions, a very high Coefficient of Variation (COV).

Numerical Simulations of Blast Wave Propagation After a High-Energy Explosion

Numerical Simulations of Blast Wave Propagation After a High-Energy Explosion

A two-scale approach to widen a predictive blast propagation model around a hemicylindrical obstacle

The aim of the present paper was to report on an experimental study of the characterization of a blast wave initiated by a solid explosive and its interaction with a rigid obstacle in the form of a hemicylinder. Pressure transducers located along the path of the blast wave and high-speed imaging allow (1) the measurement of the overpressure at different locations and (2) the characterization of the blast wave inception, propagation, and reflection off the hemicylinder. The scaling effect has been investigated by performing experiments in two different facilities, where one is at twice the scale of the other.