The Study on the Shock Wave Propagation Rule of a Gas Explosion in a Gas Compartment

Combined with the k-ε turbulence model of general application, a refined finite element model of a utility tunnel’s gas compartment filled with the methane/air mixture is developed. A series of analyses are made by using the powerful industry-leading computational fluid dynamics (CFD) software flame acceleration simulator (FLACS) to study the shock wave propagation rule in the gas compartment. The longitudinal and transversal distribution laws of the explosion shock wave are gained taking into consideration the spatial characteristics of the gas compartment. The influences of a few parameters, such as initial conditions and section size of the gas compartment, on the shock wave propagation rule are further discussed. The basic procedure for predicting the peak pressure of the blast wave is provided by considering the initial conditions and the gas compartment, and the corresponding injury effect of the explosion wave on the living beings is assessed. The investigation demonstrates that the peak pressure by the coupled effect between the initial conditions is significantly influenced, especially at the upper and lower gas explosion limits. The peak pressure increases gradually as the width or height increases, and both basically meet the linear relation. The proposed method can forecast the peak pressure of the explosion shock wave in the gas compartment accurately. According to the peak pressure longitudinal and transversal distributions of the blast wave, the peak pressure is far greater than the killing pressure threshold in the underground and closed space; consequently, it is not safe for the living beings in the gas compartment.

Pathomorphological markers of blast-induced brain injury

Background. Recently, interest in blast-induced brain injuries has been increasing due to military events and the use of explosive devices in eastern Ukraine. Considering the diagnostic uncertainty regarding the specific signs of brain injury after the distant action of an blast shock wave, the danger of prognostic consequences, the increase of the cases of explosive injury number, we consider that selected for study topic is relevant. Objective. Purpose – determination of pathomorphological changes of the brain after the action of the blast wave. Methods. To solving this purpose, a retrospective analysis of 280 cases of fatal military blast injuries was conducted. We selected 6 cases for microscopic examination of the brain. For histological examination, samples were taken from different parts of the brain. Results. Analysis of 280 deaths due to explosive trauma showed that 58.9% of the dead (165) had a traumatic brain injury, and in 131 cases it was accompanied by fractures of the bones of the vault and the base of the skull. Isolated traumatic brain injury was detected in only 33 cases (11.8%). Age distribution analysis of the dead people showed that 67.5% of the dead were between the ages of 21 and 40. Histopathological analysis of brain samples from the dead allowed to identify the characteristic signs of blast-induced brain injury in the form of diffuse formation of perivascular microhemorrhages with partial or complete separation of the vascular wall from the neuropil. Conclusion. The complex of microscopic signs in the brain, namely, the separation of vascular wall from neuroglia with the formation of perivascular space, fragmentation of these vessels walls, erythrocytes hemolysis, hemorrhage in the newly formed perivascular spaces, are direct evidences of the blast wave action.

Evaluation of Blast Simulation Methods for Modeling Blast Wave Interaction with Human Head

Blast induced traumatic brain injury (bTBI) research is crucial in asymmetric warfare. The finite element analysis is an attractive option to simulate the blast wave interaction with the head. The popular blast simulation methods are ConWep based pure Lagrangian, Arbitrary-Lagrangian-Eulerian, and Coupling method. This study examines the accuracy and efficiency of ConWep and Coupling methods in predicting the biomechanical response of the head. The simplified cylindrical, spherical surrogates and biofidelic human head models are subjected to field-relevant blast loads using these methods. The reflected overpressures at the surface and pressures inside the brain from the head models are qualitatively and quantitatively evaluated against the available experiments. Both methods capture the overall trends of experiments. Our results suggest that the accuracy of the ConWep method is mainly governed by the radius of curvature of the surrogate head. For the relatively smaller radius of curvature, such as cylindrical or spherical head surrogate, ConWep does not accurately capture decay of reflected blast overpressures and brain pressures. For the larger radius of curvature, such as the biofidelic human head, the predictions from ConWep match reasonably well with the experiment. For all the head surrogates considered, the reflected overpressure-time histories predicted by the Coupling method match reasonably well with the experiment. Coupling method uniquely captures the shadowing and union of shock waves governed by the geometry driven flow dynamics around the head. Overall, these findings will assist the bTBI modeling community to judiciously select an objective-driven modeling methodology.