Effect of Charge Shape and Initiation Configuration of Explosive Cylinders Detonating in Free Air on Blast-Resistant Design

This paper investigates the influence of the cylindrical charge characteristics, i.e., the length-to-diameter ratio, orientation, and initiation configuration, on the blast loads (peak overpressure and maximum impulse). Three different initiation configurations were considered, i.e., at the center, at one end, and at both ends. Numerical models were developed for the spherical and cylindrical charges. The numerical results were analyzed along the gauge lines at different azimuth angles around the cylindrical charges. Some important observations were made. Neglecting the charge shape effect, the peak overpressure (maximum impulse) in the near field generated from centrally initiated cylindrical charges can be underestimated by a factor as high as 3.0 (1.9). Therefore, the cylindrical charge shape should be explicitly modeled in the numerical simulations for the blast-resistant design of protective structures subjected to near-field detonations. It is confirmed that the shock front heals into a spherical one in the far field. Hence, the blast loads generated from the spherical charge of the same mass can be used. In addition, the influence range, beyond which the charge shape effect can be neglected, is $5.7\mathrm{m}/{\mathrm{kg}}^{1/3}$ for the impulse, which is about twice that for the overpressure ($3.2\mathrm{m}/{\mathrm{kg}}^{1/3}$). In general, the maximum values of blast loads resulted by the three considered initiation configurations can be sorted in descending order, i.e., $\text{at}\text{one}\text{end}>\text{at}\text{the}\text{center}>\text{at}\text{both}\text{ends}$. The initiation configuration at one end (at the center) has the largest influence range of $3.9\mathrm{m}/{\mathrm{kg}}^{1/3}$ ($5.7\mathrm{m}/{\mathrm{kg}}^{1/3}$) for the overpressure (impulse) among the three considered initiation configurations.