Blast Wave Shaping by Altering Cross-Sectional Shape

Standoff distances for people and equipment are determined using a scaled distance calculation that assumes a uniform distribution of explosive energy, which only occurs with center-initiated spherical charges in free air without ground effects. There is a significant amount of data available for spheres and cylinders in air and hemispheres on the ground, but little has been published for other geometries. Published studies of spherical, cylindrical, and planar charges demonstrate that there is a focus on the blast wave resulting from charge geometry. From these studies, it appears that the highest overpressure occurs in the orientation of the largest presented surface area. This paper presents experimental pressure data recorded from the detonation of spherical, cylindrical, and cubic charges at two scaled distances. The non-spherical charges were instrumented normal to two adjacent sides and the interjacent edge. The pressure normal to the sides of the cubic and cylindrical charges was up to 1.5 times that of the spherical charge in the near field, but lower in the far-field indicating that a simple multiplication factor will not accurately predict the overpressure over distance for complex charges from spherical data. The sides of the cubic charge produced a near field overpressure relative to its surface area consistent with those observed from the side and end of the cylindrical charge. In the far-field, the pressure from the sides of the charge was less than that of the sphere indicating that there is a lateral movement of energy behind the shock front causing a reversal of peak pressure in the measured orientations