Blast Wave Propagation Research Articles

One-way approximation for the simulation of weak shock wave propagation in atmospheric flows.

A numerical scheme is developed to simulate the propagation of weak acoustic shock waves in the atmosphere with no absorption. It generalizes the method previously developed for a heterogeneous medium [Dagrau, Rénier, Marchiano, and Coulouvrat, J. Acoust. Soc. Am. 130, 20-32 (2011)] to the case of a moving medium. It is based on an approximate scalar wave equation for potential, rewritten in a moving time frame, and separated into three parts: (i) the linear wave equation in a homogeneous and quiescent medium, (ii) the effects of atmospheric winds and of density and speed of sound heterogeneities, and (iii) nonlinearities. Each effect is then solved separately by an adapted method: angular spectrum for the wave equation, finite differences for the flow and heterogeneity corrections, and analytical method in time domain for nonlinearities. To keep a one-way formulation, only forward propagating waves are kept in the angular spectrum part, while a wide-angle parabolic approximation is performed on the correction terms. The numerical process is validated in the case of guided modal propagation with a shear flow. It is then applied to the case of blast wave propagation within a boundary layer flow over a flat and rigid ground.

Prediction of globe rupture caused by primary blast: a finite element analysis

Although a human eye comprises less than 0.1% of the frontal body surface area, injuries to the eye are found to be disproportionally common in survivors of explosions. This study aimed to introduce a Lagrangian–Eulerian coupling model to predict globe rupture resulting from primary blast effect. A finite element model of a human eye was created using Lagrangian mesh. An explosive and its surrounding air domain were modelled using Eulerian mesh. Coupling the two models allowed simulating the blast wave generation, propagation and interaction with the eye. The results showed that the peak overpressures caused by blast wave on the corneal apex are 2080, 932.1 and 487.3 kPa for the victim distances of 0.75, 1.0 and 1.25 m, respectively. Higher stress occurred at the limbus, where the peaks for the three victim distances are 25.5, 14.1 and 6.4 MPa. The overpressure threshold of globe rupture was determined as 2000 kPa in a small-scale explosion. The findings would provide insights into the mechanism of primary blast-induced ocular injuries.

Cinematographic investigations of the explosively driven dispersion and ignition of solid particles

We present results of an experimental study of blast wave propagation and particle dispersion induced by a free-field detonation of spherical charges made of a 125 g C-4 explosive surrounded by inert or reactive particles. Visualization of the flow was performed with a high-frame-rate video camera. Background oriented Schlieren (BOS) methods were adapted to process the images that allowed the detection of the shock waves. BOS analysis also revealed that particles form agglomerates, which may generate precursor perturbations on the recorded pressure signals. While inert glass particles notably delay the shock, the combustion of aluminium particles can accelerate it, especially if they are small atomized or flaked particles. When a mixture of inert glass particles with reactive particles is dispersed, the agglomerates are formed by coalescence of both materials.

Experimental and Numerical Investigation of the Mechanism of Blast Wave Transmission Through a Surrogate Head

This work is to develop an experiment-validated numerical model to elucidate the wave transmission mechanisms through a surrogate head under blast loading. Repeated shock tube tests were conducted on a surrogate head, i.e., water-filled polycarbonate shell. Surface strain on the skull simulant and pressure inside the brain simulant were recorded at multiple locations. A numerical model was developed to capture the shock wave propagation within the shock tube and the fluid-structure interaction between the shock wave and the surrogate head. The obtained numerical results were compared with the experimental measurements. The experiment-validated numerical model was then used to further understand the wave transmission mechanisms from the blast to the surrogate head, including the flow field around the head, structural response of the skull simulant, and pressure distributions inside the brain simulant. Results demonstrated that intracranial pressure in the anterior part of the brain simulant was dominated by the direct blast wave propagation, while in the posterior part it was attributed to both direct blast wave propagation and skull flexure, which took effect at a later time. This study served as an exploration of the physics of blast-surrogate interaction and a precursor to a realistic head model.

Blast Wave Propagation and Casualty Distribution Evaluation in the Subway Station Subjected to Internal Blast Loading

Blast Wave Propagation and Casualty Distribution Evaluation in the Subway Station Subjected to Internal Blast Loading

Blast response and failure analysis of pile foundations subjected to surface explosion

This paper presents the response of pile foundations to ground shocks induced by surface explosion using fully coupled and non-linear dynamic computer simulation techniques together with different material models for the explosive, air, soil and pile. It uses the Arbitrary Lagrange Euler coupling formulation with proper state material parameters and equations. Blast wave propagation in soil, horizontal pile deformation and pile damage are presented to facilitate failure evaluation of piles. Effects of end restraint of pile head and the number and spacing of piles within a group on their blast response and potential failure are investigated. The techniques developed and applied in this paper and its findings provide valuable information on the blast response and failure evaluation of piles and will provide guidance in their future analysis and design.

Theoretical Prediction of Pressure and Temperature of an Aluminized High Explosive in Underwater Explosion

AbstractThe blast wave propagation in underwater explosion was studied. The shock propagation in water medium was different from that in air. The blast effect in water lasted longer and offered resistance to the expansion of hot gases and release of energy. A theoretical analysis of the expansion of blast wave in water was carried out and numerical results for pressures and temperatures were obtained as functions of distance and time by analytically solving the governing equations. The initial peak pressures of blast waves, which were required for theoretical analysis were calculated using the blast wave theory. Underwater blasts with different weights (0.045, 0.5, and 1.0 kg) of the aluminized high explosive HBX‐3 were conducted to record pressure as a function of distance and time from the blast point. Theoretical results were compared with experimental data and empirical data for HBX‐3 from literature. Since the measurement of pressure and temperature at close proximity of point of detonation is difficult, theoretical modeling of underwater blast is of significant importance.

Impact of a shock wave on a structure strengthened by rigid polyurethane foam

The use of the rigid polyurethane foam (RPF) to strengthen sandwich structures against blast terror has great interests from engineering experts in structural retrofitting. The aim of this study is to use the RPF to strengthen sandwich steel structure under blast load. The sandwich steel structure is assembled to study the RPF as structural retrofitting. The filed blast test is conducted. The finite element analysis (FEA) is also used to model the sandwich steel structure under shock wave. The sandwich steel structure performance is studied based on detonating different TNT explosive charges. There is a good agreement between the results obtained by both the field blast test and the numerical model. The RPF improves the sandwich steel structure performance under the blast wave propagation.

Hydrodynamic simulations of the interaction of supernova shock waves with a clumpy environment: the case of the RX J0852.0−4622 (Vela Jr) supernova remnant

Observations in all electromagnetic bands show that many supernova remnants (SNRs) have a very aspherical shape. This can be the result of asymmetries in the supernova explosion or a clumpy circumstellar medium. We study the generation of inhomogeneities and the mixing of elements arising from these two sources in multidimensional hydrodynamic simulations of the propagation of a supernova blast wave into a cloudy environment. We model a specific SNR, Vela Jr (RX J0852.0-4622). By comparing our results with recent observations, we can constrain the properties of the explosion. We find that a very energetic explosion of several 10^{51} erg occurring roughly about 800 years ago is consistent with the shape and emission of the SNR, as well as a supernova with an energy closer to the canonical value of 10^{51} erg a few thousand years ago.

Wave and fracture propagation in continuum and faulted rock masses: distinct element modeling

In this study, to investigate the dynamic fracture mechanism of blast-induced fracturing of rock mass around a blasthoe, two-dimensional (2D) distinct element method was used. The dynamic stresses, material status, and velocity vectors are shown to investigate rock mass failure subjected to blast load. On the other hand, rock masses consist of intact rock and discontinuities such as faults, joints, and bedding planes. The presence of such discontinuities in rock masses dominates the response of jointed rock masses to static and dynamic loading. This paper focuses on the effect of fault orientation on dynamic fracturing of rock mass. In order to investigate the effect of faults on dynamic fracturing of rock mass, a numerical simulation was conducted. The two-dimensional (2D) distinct element code was used to simulate the effect of a fault on rock failure and stress distribution through the rock mass due to blast wave propagation. The blast loading history was calculated using analytical method and was applied to the blasthole walls. Accordingly, the interaction of explosive energy transferred to the rock mass from the blasthole was examined as a function of distance to the fault plane. A Mohr–Coulomb material model was used for host rock to allow for plastic failure calculations. The study can be divided in two parts: firstly, surface blast and secondly, underground blast. The conducted numerical study describes the role of fault in blasting in a qualitative manner. On the other hand, a free-face boundary was considered as a common blast operation which is conducted in surface mining. In second part, blast was modeled in underground operations at presence of in situ stresses. The results in such areas showed predominant effect of pre-stresses as well as fault orientation on fracture propagation.

Analytic computations of nonideal corrections to blast wave overpressure predictions at high altitudes

AbstractIn this paper, the effects of temperature, pressure, winds, moisture, and molecular content on the propagation of blast waves at high altitudes are investigated. These cause refractions and attenuations which modify the recorded ground overpressures from the ideal predictions. By coupling these effects together, the nonideal corrections to the overpressures are estimated by applying approximations which are dependent on the angle of propagation of the blast wave.

Computational modeling of human head under blast in confined and open spaces: primary blast injury

In this paper, a computational modeling for biomechanical analysis of primary blast injuries is presented. The responses of the brain in terms of mechanical parameters under different blast spaces including open, semi-confined, and confined environments are studied. In the study, the effect of direct and indirect blast waves from the neighboring walls in the confined environments will be taken into consideration. A 50th percentile finite element head model is exposed to blast waves of different intensities. In the open space, the head experiences a sudden intracranial pressure (ICP) change, which vanishes in a matter of a few milliseconds. The situation is similar in semi-confined space, but in the confined space, the reflections from the walls will create a number of subsequent peaks in ICP with a longer duration. The analysis procedure is based on a simultaneous interaction simulation of the deformable head and its components with the blast wave propagations. It is concluded that compared with the open and semi-confined space settings, the walls in the confined space scenario enhance the risk of primary blast injuries considerably because of indirect blast waves transferring a larger amount of damaging energy to the head.

A fitting formula for radiative cooling based on non-local thermodynamic equilibrium population from weakly-ionized air plasma

A fitting formula for radiative cooling with collisional-radiative population for air plasma flowfield has been developed. Population number densities are calculated from rate equations in order to evaluate the effects of nonequilibrium atomic and molecular processes. Many elementary processes are integrated to be applied to optically-thin plasmas in the number density range of 1012/cm3 ≤ N ≤ 1019/cm3 and the temperature range of 300 K ≤ T ≤ 40,000 K. Our results of the total radiative emissivity calculated from the collisional-radiative population are fitted in terms of temperature and total number density. To validate the analytic fitting formula, numerical simulation of a laser-induced blast wave propagation with the nonequilibrium radiative cooling is conducted and successfully reproduces the shock and plasma wave front time history observed by experiments. In addition, from the comparison between numerical simulations with the radiation cooling effect based on the fitting formula and those with a gray gas radiation model that assumes local thermodynamic equilibrium, we find that the displacement of the plasma front is slightly different due to the deviation of population probabilities. By using the fitting formula, we can easily and more accurately evaluate the radiative cooling effect without solving detailed collisional-radiative rate equations.

Computer simulation of underground blast response of pile in saturated soil

This paper treats the blast response of a pile foundation in saturated sand using explicit nonlinear finite element analysis, considering complex material behavior of soil and soil–pile interaction. Blast wave propagation in the soil is studied and the horizontal deformation of pile and effective stresses in the pile are presented. Results indicate that the upper part of the pile to be vulnerable and the pile response decays with distance from the explosive. The findings of this research provide valuable information on the effects of underground explosions on pile foundation and will guide future development, validation and application of computer models.

Research progress experimental and detection method on pulmonary blast injury

Due to the air-filled alveoli and delicate vascular structure,the lung is the most easily damaged organ when human or animal is subjected to a shock wave.Primary pulmonary blast injury resulting from shock wave is an important cause of trauma not only in military conflicts but also in terrorism or accidents involving civilians.The physiological,pathological and biochemical changes after blast injury may lead to inflammatory response,cell apoptosis in the lung,boost the activation of cytokines including TNF-α,IL-6,IL-8 and IL-1β,and finally result in acute respiratory distress syndrome (ARDS).This paper presents the evolution and characteristics of pulmonary blast injury,and demonstrates four relevant experimental setups including biological shock tube,segmented shock wave generator,mini blast wave generator and laser-induced stress wave generator.Besides,this paper reviews the scoring system of pulmonary blast injury,pathological and biochemical measurement aiming to provide helpful reference to establish pulmonary blast injury models. Key words: Shock wave; Lung injury; Experimental settings

Aeroelastic response of rocket nozzles to asymmetric thrust loading

The aeroelastic response of rocket nozzles subjected to combined axial thrust and side loads is investigated using a particular computational technique. The technique uses two-way “loose” coupling between an accurate flow solver and an accurate structural-dynamics solver to accurately capture the behavior of the internal flow, the behavior of the nozzle wall, and the interactions between the fluid-dynamic and structural-dynamic phenomena. It is shown that the technique captures the fluid-dynamic phenomena that are known to contribute to nozzle side loads, including the asymmetry in the propagation of the initial blast wave, the asymmetry in the separation lines, the pressure pulsations at the separation lines, the transition of separated flow patterns, and various flow instabilities. It is also shown that the computational technique couples the fluid-dynamic and the structural-dynamic solutions with an accuracy and a resolution that are sufficient for accurate prediction of the aeroelastic response modes in the system. The fluid-dynamics solver is validated for shock-induced flow separations in a sub-scale J-2S nozzle, while the structural-dynamic solver is validated for a typical dynamic response in a rocket nozzle. The two-way loose coupling methodology is validated for the flutter of a flat plate in supersonic flow, and the validation results are discussed and assessed with respect to the fitness of the computational technique for the prediction of the aeroelastic response of typical actual nozzle configurations. Finally, the side loads are computed for a J-2S nozzle with rigid walls and with flexible walls, and the results for the two types of walls are analyzed and compared. It is found that allowing aeroelastic coupling significantly affects the response of the nozzle and the predicted side loads. It is speculated that the computational technique investigated in this work combines all the elements required to accurately predict and simulate the aeroelastic response of a rocket nozzle to non-symmetric thrust, and that such a technique can be used to study and investigate side load phenomena in rocket nozzles in detail and also as a design tool for rocket nozzles. The technique is also speculated to be effective and appropriate for other fluid–structure interaction problems within an appropriate range of aeroelastic regimes.

Influence of Open Channel on Explosion-Induced Vibration Wave Propagation

Hazard control of explosion-induced vibration is an important issue which cannot be ignored in blasting engineering. Its influence range and damage scale are affected by the shock wave energy. This study applied the LS-DYNA software and adopted the Arbitrary Lagrangian-Eulerian method for numerical analysis to simulate the propagation of blast waves caused by the surface blast of C-4 explosives in a semi-infinite space in order to explore the effectiveness of Open Channel Grooves in vibration isolation. The analysis shows that the finite element method can properly simulate the dynamic characteristics of soil in an explosion; with the distance moving away from the explosion point, the shock wave gradually decays. Open Channel Grooves have a significant effect on attenuating the propagation of detonation waves. The attenuation degree is related to the width and depth of the groove, and the impact of the depth is greater than that of the width. This study can be used as a reference in hazard control of explosion-induced vibration for relevant engineering projects.

Investigation on the Ignition Over Pressure Related to Launch Vehicle Lift-off

Several transient events occur during the startup of the Solid Rocket Motor (SRM) during the launch vehicle lift-off. Each event produces a complex transient signal and requires systematic assessment. The event discussed in this paper is Ignition Over Pressure (IOP). This Ignition Over Pressure is resulting from fluid dynamic compression of the accelerating plume gas, subsequent rarefaction and propagation during the pressure rise rate period in the rocket combustion chamber. These high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and its surrounding structure. This wave behaves as a blast or shock wave characterized by a positive triangular shaped first pulse and negative half sine wave second pulse. The pulse travels upwards towards the propulsion system and has the potential to overload the individual elements or exciting overall vehicle dynamics. The later effect results from the phase difference of the wave from one side of the vehicle to the other due to the skew in the ignition of the strap-on boosters. In the case of the launchers, the mechanical stress due to the ignition over pressure wave comes, in addition to the acoustic constraint due to the jet noise. The over pressure phasing or ΔP environment, because of its spectral content as well as amplitudes becomes a crucial input for the design of sub-assemblies viz., thermal shields, and pay loads etc. In this paper, an attempt is made to numerically visualize the propagation of the blast wave causing the unsteady pressure oscillations during the transient pressure rise in the combustion chamber. To understand further, pressure measurements have been made at different heights along the umbilical tower during the solid rocket motor lift-off with the presence of jet deflectors, in order to capture the shock propagation phenomena. From the results, it appears that a sudden shock front that is generated during flow development within the rocket nozzle leaves a clear signature in the form of a well defined peak at typical time intervals. This overpressure amplitude seems to be related to the slope of the combustion chamber pressure rise rate during the transient period. It is also observed that the shock front initially propagates at supersonic speed but decays with time later. Similarly, the magnitude of the IOP peaks are also seen to decay with distance.

Computational analysis of fluid–structure interaction based blast-mitigation effects

Advanced non-linear dynamics, finite element computational methods and tools are utilized in order to assess the blast wave mitigation potential of the fluid–structure interaction phenomena involving rigid and deformable structures. The employed computational methods and tools are verified and validated by first demonstrating that they can quite accurately reproduce analytical solutions for a couple of well-defined blast wave propagation and interaction problems. Then the methods/tools are used to investigate the fluid–structure interaction phenomena involving deformable structures while accounting for both the interaction of the incident blast wave with the structure and for the structure-motion induced blast wave (at the back-face of the structure). To assess the role of the structure deformability, i.e. the role of the shock waves generated within the structure, the results obtained are compared with their rigid structure counterparts. This comparison established that no additional structure-deformability-related blast-mitigation effects are observed in the case of fully supported blast wave loading while, under exponentially decaying blast wave loading, such effects are observed but only under conditions when the shock wave propagation time within the structure is comparable with the incident wave decay time.

Shock and blast waves mitigation

Shock and blast waves propagation in complex media is one of the most important topics of current shock wave research. In the past, most of the shock wave researches dealt with shock phenomena in relatively simple configurations and fluid flow conditions. However, accounting for modern developments of shock research and its evolution into interdisciplinary applications, there is a need to study wave phenomena in complex environments such as those consisting of complex constituents. Furthermore, the prediction of damage caused by blast waves, generated by largescale explosions (see Figs. 1 and 2), either from terrorist attacks or industrial hazards has been a research problem that needs further understanding from disaster prevention point of view. These important issues have two common features: (1) understand the complex flow field induced by blast and shock waves that pass through complex media and (2) help designing new devices for protection against blast loading.