Computational fluid dynamics is a useful tool for investigating various cases when estimating the physical hazard of high explosives. This paper presents a test case to discuss the effect of a rigid barrier wall on the blast wave behavior of a high explosive. A condensed matter analysis program for high-energy materials (KHT2009) was used to obtain the properties of the detonation products. We modeled the detonation products with the equation of state for an ideal gas, and the initiation process of the high explosive was neglected. The wall was close to the high explosive and interacted with the initial blast wave and detonation products. An additional higher wall was installed over a standard barrier wall around an azimuth angle of 0°. The azimuthal distributions of the peak overpressures were compared for previously obtained experimental results and the present numerical results. The multiple reflected and diffracted waves off the wall produced complex flow patterns that were responsible for the azimuthal distribution of the peak overpressure. To secure a longer distance and time before the reflected wave from the additional higher wall intensifies the incident blast wave along 180°, and to achieve greater mitigation beyond and near the wall along 0°, we recommend that the additional higher wall be located as far as possible from the high explosive.

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A new layer-by-layer coating method to prepare triaminotrinitrobenzene/cyclotetramethylenetetranitramine (TATB/HMX) composite materials has been developed. By using fluoroelastomer as the binder, a TATB/HMX composite, which exhibited significantly lower mechanical sensitivity than that of raw HMX, was obtained. Scanning electron microscopy, energy-dispersive spectrometer, differential scanning calorimetry and fourier-transform infrared spectroscopy were utilized to investigate the structure of the composite particles. The results indicated that the surface of the raw HMX particles is tightly covered with TATB, and a hydrogen bonding force is formed inside the composite particles. The characterization of differential scanning calorimetry, before and after coating, shows that the TATB/HMX composite maintains good thermal stability. Moreover, the theoretical density of the TATB/HMX composite reaches 1.91 g･cm^-3, and the theoretical explosion velocity is 8965 m･s^-1.

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In this study, we used high-speed photography and measurements with a piezo film stress gauge to investigate electrical discharge after the application of an energy discharge to a thin metal wire in a liquid energy material (nitromethane) in a vessel. The objective was to expand the applications of electric discharge fracturing technology in urban areas. Explosion of the metal wire occurred when a high voltage was applied, and a shock wave with relatively low pressure was generated. However, the reaction of the liquid energy material did not happen immediately after the discharge, but an intense explosive reaction gradually occurred after the wire explosion. The reaction products gradually expanded over time into a hemispherical shape at an expansion rate of ～185 m･s ^-1.

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Advanced closed-loop control of thrust and mixture ratio of hybrid rockets is planned by combing a fuel mass flow rate control technique with a real-time fuel regression measurement. The latter technique is enabled by a multi-materialadditive-manufactured solid fuel with an integrated sensor probe structure. This work investigated the fuel regression behavior of polylactic acid (PLA) fuel used for the main material of this type of solid fuels. Rectangular slab fuels and cylindrical fuel grains were manufactured by Fused Filament Fabrication (FFF) and fired in an optically accessible slab burner and a lab-scale motor, respectively. The cylindrical fuel grains had more than 2 times larger regression rates than rectangular slab fuels even with the same PLA filament. One of the main factors causing this large difference can be an anisotropy in the fuel regression rate behavior of the solid fuels manufactured by FFF.

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