Explosive Blast Wave Research Articles

Effect of blast orientation, multi-point blasts, and repetitive blasts on brain injury

Explosions in the battlefield can result in brain damage. Research on the effects of shock waves on brain tissue mainly focuses on the effects of single-orientation blast waves, while there have been few studies on the dynamic response of the human brain to directional explosions in different planes, multi-point explosions and repetitive explosions. Therefore, the brain tissue response and the intracranial pressure (ICP) caused by different blast loadings were numerically simulated using the CONWEP method. In the study of the blast in different directions, the lateral explosion blast wave was found to cause greater ICP than did blasts from other directions. When multi-point explosions occurred in the sagittal plane simultaneously, the ICP in the temporal lobe increased by 37.8 % and the ICP in the parietal lobe decreased by 17.6 %. When multi-point explosions occurred in the horizontal plane, the ICP in the frontal lobe increased by 61.8 % and the ICP in the temporal lobe increased by 12.2 %. In a study of repetitive explosions, the maximum ICP of the second blast increased by 40.6 % over that of the first blast, and that of the third blast increased by 61.2 % over that of the second blast. The ICP on the brain tissue from repetitive blasts can exceed 200 % of that of a single explosion blast wave.

КОНЦЕПЦІЯ ПІДВИЩЕННЯ БЕЗПЕКИ ВУЗЛІВ РОЗПОДІЛЬНОЇ ЕНЕРГЕТИЧНОЇ ІНФРАСТРУКТУРИ УКРАЇНИ

The issue of one of the problems that arose in the energy infrastructure of Ukraine as a result of the regular destruction of its facilities during the war is considered. It concerns ways of increasing the security of nodes of the distribution system of the energy infrastructure of Ukraine during its further restoration and modernization. An overview of the relevant issues that arise when using different methods to achieve the set goal is made. The importance of the problem of protection of electrical substations of the energy distribution infrastructure and the need for appropriate research and development to create an optimal method of protection are indicated. The urgency of developing a method and means of protection of an important element of substations (power transformer) is noted. One of the variants of the optimal concept of the corresponding protection is described. It provides for the location of transformers in an earthen niche, accordingly formed and decorated with auxiliary elements. This option is simple, technological and economically beneficial. This method of protecting transformers should protect them from fragments of explosive devices and blast waves. The proposed concept has room for improvement. Ref. 4, fig. 2. Keywords: power grid, transformer, safety, shelter, concept.

FTP1.4 Computer Blast wave and Shrapnel Simulation in Unity

Abstract Aims A computer simulation to show the effects of an explosive device's blast wave and shrapnel injuries to humans. Methods Unity 3D project written in C# with real time physics showing the effects on people and listing probable injuries sustained. Results An explosive mass of 0.1kg to 100kg PTEN can be simulated showing the evolving blast wave and up to 100,000 shrapnel particles. The blast wave can show the maximum overpressure, velocity of the shock front and temperature Video: https://youtu.be/ICH2xHR6678. The shrapnel is simulated with the physics engine including velocity, energy of injury and body/limb hit points to calculate their effect. A model of the Manchester Arena is used as an example. Example blastwave data: Conclusions This novel approach to simulation showcases what is possible with computer simulation. Next steps are verification of data and building of more models. A higher detailed human model is being worked on which includes organs and bones.

The Imbalance of Astrocytic Mitochondrial Dynamics Following Blast-Induced Traumatic Brain Injury.

Mild blast-induced traumatic brain injury (bTBI) is a modality of injury that has been of major concern considering a large number of military personnel exposed to explosive blast waves. bTBI results from the propagation of high-pressure static blast forces and their subsequent energy transmission within brain tissue. Exposure to this overpressure energy causes a diffuse injury that leads to acute cell damage and, if chronic, leads to detrimental long-term cognitive deficits. The literature presents a neuro-centric approach to the role of mitochondria dynamics dysfunction in bTBI, and changes in astrocyte-specific mitochondrial dynamics have not been characterized. The balance between fission and fusion events is known as mitochondrial dynamics. As a result of fission and fusion, the mitochondrial structure is constantly altering its shape to respond to physiological stimuli or stress, which in turn affects mitochondrial function. Astrocytic mitochondria are recognized to play an essential role in overall brain metabolism, synaptic transmission, and neuron protection. Mitochondria are vulnerable to injury insults, leading to the increase in mitochondrial fission, a mechanism controlled by the GTPase dynamin-related protein (Drp1) and the phosphorylation of Drp1 at serine 616 (p-Drp1s616). This site is critical to mediate the Drp1 translocation to mitochondria to promote fission events and consequently leads to fragmentation. An increase in mitochondrial fragmentation could have negative consequences, such as promoting an excessive generation of reactive oxygen species or triggering cytochrome c release. The aim of the present study was to characterize the unique pattern of astrocytic mitochondrial dynamics by exploring the role of DRP1 with a combination of in vitro and in vivo bTBI models. Differential remodeling of the astrocytic mitochondrial network was observed, corresponding with increases in p-Drp1S616 four hours and seven days post-injury. Further, results showed a time-dependent reactive astrocyte phenotype transition in the rat hippocampus. This discovery can lead to innovative therapeutics targets to help prevent the secondary injury cascade after blast injury that involves mitochondria dysfunction.

Solution of Unsteady Flow Equations for Nanoscale Heat and Mass Transfer in Diverse Applications

Abstract A new innovative stable time-dependent compressible flow solution over the order of nanoseconds is provided here for wide-ranging critically important challenging applications. Specifically, a solution of the highly complex unsteady high speed oscillating compressible flow field inside a cylindrical tube, closed at one end with a piston oscillating at very high resonant frequency at the other end, has been obtained numerically, assuming one-dimensional, viscous, and heat-conducting flow, by solving the appropriate fluid dynamic and energy equations. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. In successfully predicting the time-dependent results/data, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide ranging research, design, development, analysis, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid-structure interaction heat transfer enhancement, nanoscale heat and mass transfer, diverse range of advanced fluidics, biofluidics/bio-engineering, and fluidic pyrotechnic initiation devices. It can further be easily extended to cover muzzle blasts and high energy nuclear explosion blast wave propagations in one-dimensional and/or radial spherical coordinates with or without including energy generation/addition terms. No other solution exists for such applications.

Time of arrival as a diagnostic for far-field high explosive blast waves

The ability to accurately determine blast loading parameters will enable more fundamental studies on the sources of blast parameter variability and their influence on the magnitude and form of the loading itself. This will ultimately lead to a better fundamental understanding of blast wave behaviour, and will result in more efficient and effective protective systems and enhanced resilience of critical infrastructure. This article presents a study on time of arrival as a diagnostic for far-field high explosive blasts, and makes use of the results from a large number of historic tests and newly performed experiments where the propagating shock front was filmed using a high-speed video (HSV) camera. A new method for optical shock tracking of far-field blast tests is developed and validated, and full-field arrival time results are compared against those determined from the historic data recorded using traditional pressure gauges. Arrival time variability is shown to be considerably lower than peak pressure and peak specific impulse, and is shown to decrease exponentially with increasing scaled distance. Further, the method presented in this article using HSV cameras to determine arrival time yields further reductions in variability. Finally, it is demonstrated that the method can be used to accurately determine far-field TNT equivalence of high explosives.

Solution of Unsteady Fluid Dynamic and Energy Equations for High-Speed Oscillating Compressible Flows and Blast Wave Propagations

Abstract A solution of the highly complex unsteady high-speed oscillating compressible flow field inside a cylindrical tube has been obtained numerically, assuming one-dimensional, viscous, and heat conducting flow, by solving the appropriate fluid dynamic and energy equations. The tube is approximated by a right circular cylinder closed at one end with a piston oscillating at very high resonant frequency at the other end. An iterative implicit finite difference scheme is employed to obtain the solution. The scheme permits arbitrary boundary conditions at the piston and the end wall and allows assumptions for transport properties. The solution would also be valid for tapered tubes if the variations in the cross-sectional area are small. In successfully predicting the time-dependent results, an innovative simple but stable solution of unsteady fluid dynamic and energy equations is provided here for wide-ranging research, design, development, analysis, and industrial applications in solving a variety of complex fluid flow heat transfer problems. The method is directly applicable to pulsed or pulsating flow and wave motion thermal energy transport, fluid–structure interaction heat transfer enhancement, and fluidic pyrotechnic initiation devices. It can further be easily extended to cover muzzle blasts and nuclear explosion blast wave propagations in one-dimensional and/or radial spherical coordinates with or without including energy generation/addition terms.

Damage analysis of explosion blast wave to rocket structure and payload

The explosion of rocket poses a serious threat to the payload in it. LS-DYNA software is used to analyze co-bottom explosion of the third stage in flight. The damage mechanism of explosion to the structure of the rocket body and the storage tank is mainly studied, and effect of shock peak overpressure, positive pressure time and specific impulse on the payload is evaluated. The results show that: the model can reflect the destruction mechanism of rocket structure explosion. Secondly, the closer the payload is to the explosive core, the more destructive the blast wave will be to it. What’s more, overpressure value is much larger than the upper limit of overpressure criterion, which will cause serious damage to the payload. The results may provide a reference for the safety protection design of the payload in the rocket.

Role of Endogenous and Exogenous Corticosterone on Behavioral and Cognitive Responses to Low-Pressure Blast Wave Exposure.

The complex interactions and overlapping symptoms of comorbid post-traumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) induced by an explosive blast wave have become a focus of attention in recent years, making clinical distinction and effective intervention difficult. Because dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is thought to underlie trauma-related (psycho)pathology, we evaluated both the endogenous corticosterone response and the efficacy of exogenous hydrocortisone treatment provided shortly after blast exposure. We employed a controlled experimental blast-wave paradigm in which unanesthetized animals were exposed to visual, auditory, olfactory, and tactile effects of an explosive blast wave produced by exploding a thin copper wire. Endogenous corticosterone concentrations were evaluated at different time points (before, and 3 h, 5 h and 17 days) after blast exposure. Subsequently, the efficacy of exogenous hydrocortisone (25 mg/kg-1 or 125 mg/kg-1) injected intraperitoneally 1 h after exposure was compared with that of a similarly timed saline injection. Validated cognitive and behavioral tests were used to assess both PTSD and mTBI phenotypes on days 7-14 following the blast. Retrospective analysis revealed that animals demonstrating the PTSD phenotype exhibited a significantly blunted endogenous corticosterone response to the blast compared with all other groups. Moreover, a single 125 mg/kg-1 dose of hydrocortisone administered 1 h after exposure significantly reduced the occurrence of the PTSD phenotype. Hydrocortisone treatment did not have a similar effect on the mTBI phenotype. Results of this study indicate that an inadequate corticosteroid response following blast exposure increases risk for PTSD phenotype, and corticosteroid treatment is a potential clinical intervention for attenuating PTSD. The differences in patterns of physiological and therapeutic response between PTSD and mTBI phenotypes lend credence to the retrospective behavioral and cognitive classification criteria we designed, and is in keeping with the assumption that mTBI and PTSD phenotypes may reflect distinct underlying biological and clinical profiles.

Numerical Simulation of the Response of Vehicle Cab Bottom Shell Structure under Explosive Blast Wave Based on Smoothed Particle Hydrodynamics

Numerical Simulation of the Response of Vehicle Cab Bottom Shell Structure under Explosive Blast Wave Based on Smoothed Particle Hydrodynamics

Prediction of annealed glass window response to blast loading

Several software packages that are capable of predicting the response of annealed glass windows to blast loads are evaluated, by comparison to experimental data that has been obtained from full-scale arena blast tests in the field. A total of 34 instrumented, monolithic, glass window panes were subjected to explosive blast waves of varying intensity. A series of small-scale material tests and full-scale pane tests was also performed in the laboratory to obtain mechanical properties for use in the predictive models. The utility of various software tools, based either on single degree of freedom analysis or explicit finite element analysis, is hence assessed, for use in the analysis or design of glazing under blast loading.

The science from ocular war injuries

AbstractApproximately 10% of war injuries with major trauma have eye injuries. Primary ocular blast injuries are from the transfer of kinetic energy from the explosive blast wave alone. Secondary ocular blast injuries are the most common type of blast injury (42%) from the impact of shrapnel from the explosive device itself or from exogenous debris propelled by the explosion. Tertiary ocular blast injuries (1%) are caused by indirect damage to the eye when an individual is thrown by the blast wind. Quaternary blast injures (3%) are from any other mechanism related to the blast, usually thermal burns. Quinary blast injuries are a new entity that describes a hyperinflammatory state occurring after an explosion that is thought to cause retinal vascular occlusion. IOFB injuries are given prophylactic systemic antibiotics to protect against endophthalmitis, before surgical removal. Combat eye protection (CEP) significantly reduces secondary and tertiary blast injuries, but increased the proportion with commotio retinae. We rehabilitate blind patients with the BrainPort (Wicab, USA) vision device that substitutes the sense of sight with electrotactile stimulation of the tongue and improves navigation and object recognition

An empirical model for the ignition of explosively dispersed aluminum particle clouds

An empirical model for the ignition of aluminum particle clouds is developed and applied to the study of particle ignition and combustion behavior resulting from explosive blast waves. This model incorporates both particle ignition time delay as well as cloud concentration effects on ignition. The total mass of aluminum that burns is found to depend on the model, with shorter ignition delay times resulting in increased burning of the cloud. After the Al particles ignite, a competition for oxidizer between the booster detonation products and Al ensues. A new mass-averaged ignition parameter is defined and is observed to serve as a useful parameter to compare cloud ignition behavior. Investigation of this variable reveals that both peak ignition as well as the time required to attain peak ignition, are sensitive to the model parameters. The peak degree of dissociation in the fireball is about 19 % and the associated energy can play a significant role on the dynamics of the problem. The peak degree of ionization is about 2.9 % and the energy associated with this is much lower than the other controlling factors. Overall, this study demonstrates that the new ignition model developed captures effects not included in other combustion models for the investigation of shock-induced ignition of aluminum particle clouds.

Molecular Dynamic Simulations of Blast Waves on Bilayers

Many studies using animal models have shown that blast waves cause injuries to the brain despite the lack of a direct physical impact to the brain or skull. Such injuries are manifested as biochemical, functional, or morphological alterations that result in motor and sensory deficits in addition to behavioral changes. Primary blast due to explosions causes an intense rise of atmospheric pressure, the positive phase, followed by a broader under-pressure, the negative phase. The peak overpressure reaches pressures up to 1724 kPa and the blast wave travels at speeds up to 670 m/s. Because of this high velocity, it is difficult to study the interaction of explosive blast waves with neural tissue in real time. Accordingly, we have performed molecular dynamic (MD) simulations of blast waves on myelin membranes to understand how blast waves interact with neural tissue to cause injury. In our simulations, we have created blast overpressure using a planar wall, which exerts a forces of -K(x0 - x)2; where K is the spring force constant, and x0 and x are the starting and final positions of the wall, respectively. The intensity of the overpressure wave is controlled by the spring stiffness (K) and the duration of the wave is controlled by how far the wall moves (x0 - x). Our findings demonstrate that the velocity of the blast wave is more deleterious to membranes than is the blast overpressure. At velocities above 600 m/s the negative phase can cause bilayers containing phospholipid and cholesterol to bifurcate at the bilayer center. Such structural perturbations could result in diffuse axonal injury, which is believed to play a role in the pathology of blast injury.

Experimental modeling of explosive blast-related traumatic brain injuries

This study aims to characterize the interaction of explosive blast waves through simulated anatomical systems. We have developed physical models and a systematic approach for testing traumatic brain injury (TBI) mechanisms and occurrences. A simplified series of models consisting of spherical poly(methyl methacrylate) (PMMA) shells housing synthetic gelatins as brain simulants have been utilized. A series of experiments was conducted to compare the sensitivity of the system response to mechanical properties of the simulants under high strain-rate explosive blasts. Small explosive charges were directed at the models to produce a realistic blast wave in a scaled laboratory setting. Blast profiles were measured and analyzed to compare system response severity. High-speed shadowgraph imaging captured blast wave interaction with the head model while particle tracking captured internal response for displacement and strain correlation. The results suggest amplification of shock waves inside the head near material interfaces due to impedance mismatches. In addition, significant relative displacement was observed between the interacting materials suggesting large strain values of nearly 5%. Further quantitative results were obtained through shadowgraph imaging of the blasts confirming a separation of time scales between blast interaction and bulk movement. These results lead to a conclusion that primary blast effects may potentially contribute significantly to the occurrence of military associated TBI.

Simulation of impulse effects from explosive charges containing metal particles

The propagation of an explosive blast wave containing inert metal particles is investigated numerically using a robust two-phase methodology with appropriate models to account for real gas behavior, inter-phase interactions, and inter-particle collisions to study the problem of interest. A new two-phase Eulerian–Lagrangian formulation is proposed that can handle the dense nature of the flow-field. The velocity and momentum profiles of the gas and particle phases are analyzed and used to elucidate the inter-phase momentum transfer, and its effect on the impulsive aspects of heterogeneous explosive charges. The particles are found to pick up significant amounts of momentum and kinetic energy from the gas, and by virtue of their inertia, are observed to sustain it for a longer time. The impulse characteristics of heterogeneous explosives are compared with a homogeneous explosive containing the same amount of high explosive, and it is observed that the addition of solid particles augments the impulsive loading significantly in the near-field, and to a smaller extent in the far-field. The total impulsive loading is found to be insensitive to the particle size added to the explosive charge above a certain cut-off radius, but the individual impulse components are found to be sensitive, and particles smaller than this cut-off size deliver about 8% higher total impulse than the larger ones. Overall, this study provides crucial insights to understand the impulsive loading characteristics of heterogeneous explosives.

On the Role of Ambient Reactive Particles in the Mixing and Afterburn behind Explosive Blast Waves

A hybrid two-phase numerical methodology is used to study the propagation of explosive blast waves from spherical charges of TNT and their interaction with an ambient dilute distribution of aluminum particles. The presence of these particles is found to cause perturbations at the contact surface between the inner detonation products and the outer shock-compressed air, which results in Rayleigh-Taylor instabilities at the contact surface. These instabilities grow in time, thereby creating a mixing layer characterized by enhanced mixing between the detonation products and air, resulting in afterburn. The afterburn energy release is observed to affect the pressure decay rate behind the blast wave and the speed and the strength of the secondary shock. The passage of the secondary shock through the mixing layer results in a Richtmyer-Meshkov instability, which is characterized by the creation of vorticity in the mixing layer through baroclinic torque effects. This phenomenon is observed to sustain the mixing process subsequently. The amount of mixing and afterburn are investigated for a range of aluminum particle sizes, mass loading, and initial distribution, and the role played by these particles in the growth of hydrodynamic instabilities is studied. It is shown that for the range of sizes investigated, particle size does not play a significant role in the mixing, but the initial distribution and mass loading do have appreciable impact. Furthermore, the late stages of the afterburn are observed to be self-similar, and independent of the initial triggering of the hydrodynamic instabilities. This study has provided some useful insights on the instabilities induced by ambient reactive particles in detonation flowfields and establishes a simulation capability to study turbulent two-phase processes in an explosive environment.

Analysis of blast wave propagation inside tunnel

The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave overpressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure.

A study on mesh size dependency of finite element blast structural analysis induced by non-uniform pressure distribution from high explosive blast wave

Accurate computational blast analysis can be an effective replacement for costly blast field test. HFPB (high fidelity physics based) blast analysis method including high strain rate dependent material models and appropriate blast wave models is a representative precise blast analysis method. HFPB blast analysis method can be used for various analyses such as structural analysis, retrofitting design analysis, fragmentation analysis, and energy absorbing analysis. When analyzing the behaviour of structure under blast loading by HFPB finite element methods, load gradient differences occurs dependent on the mesh size. This causes gaps between the explosive energy and internal energy of structures and the results of analysis become mesh-size-dependent. In this study, the analytical considerations were presented for mesh sensitivity due to non-uniform pressure load distribution on the structure subjected to blast wave of high explosive with relatively close stand-off. Through the analysis results, the maximum element size which ensures the mesh-size independent analysis results is suggested.

Acute blindness in a dog caused by an explosive blast

A 3-year-old, intact male, mixed breed dog was presented with a complaint of acute blindness. Ten days previously, the area where the dog was walking came under a rocket attack, and a rocket landed and exploded 300 meters away from the dog. Physical examination was unremarkable. Ophthalmoscopic examination revealed posterior segment fibrin clots and extensive vitreal hemorrhage in the right eye. A total retinal detachment (360 degrees retinal dialysis) with no evidence of hemorrhage was noted in the left eye. There was no sign of any penetrating ocular trauma, and it was assumed that the posterior segment findings were primary injuries caused by the blast wave itself. Following anti-inflammatory treatment, partial vision was restored in the right eye. Surgical re-attachment of the retina was discussed and declined by the owner. This report describes, for the first time, vitreal hemorrhage and retinal detachment as the sole injuries caused by an explosive blast wave.