Influence of charge shape and point of detonation on blast-resistant design

Charts in technical manuals and standards of practice can be used to compute incident and reflected peak overpressures and scaled impulses generated by a detonation of a high explosive. Design values are reported for spherical free-air bursts and hemispherical surface bursts as a function of scaled distance and angle of incidence, where the charges are detonated at the center of the sphere. This paper describes a numerical study with a verified and validated computational fluid dynamics code that characterizes the influence of charge shape, charge orientation, and the point of detonation within the charge on free-field incident overpressures and impulses. Analyses are performed with cylindrical charges of different aspect ratios and masses, and results are compared with those of a baseline analysis of a spherical charge. In the near field and midfield, charge shape and point of detonation affect the peak overpressure and impulse, providing values that are significantly different from those associated with a central detonation of a spherical charge of the same mass. The effect of charge shape and point of detonation can be ignored, for the purpose of a design based on impulse, at scaled distance greater than 3 m/kg1/3.