Numerical investigation of charge geometry effects on close-in blast load distribution

Existing models for predicting blast loads predominantly rely on idealized charge geometries like spheres or cylinders. However, blast load distributions from rectangular blocks, especially under close-in detonation conditions, are still not well predicted. This work develops and validates two-dimensional and three-dimensional numerical models using the finite element code LS-DYNA against experimental data. These models systematically investigate close-in blast load distributions from cylindrical and rectangular charges under center, single-end, and double-end initiation modes. The analysis details the effects of charge geometry, scaled distance, and azimuthal angle on the peak overpressure. Moreover, empirical fitting formulas for the bridge wave angle range and the deflection angle of peak pressure are derived from the numerical simulation results. Based on detonation theory, the differences in loading attributable to initiation points in contact explosions are analyzed, and an angular prediction model accounting for bridge wave formation is proposed. Furthermore, by calibrating three-dimensional simulations with accurate two-dimensional results using a ratio-based method, an empirical formula for predicting peak overpressure in close-in explosions is developed. This formula is applicable to cuboid charge geometries, initiation modes, and azimuthal angles. The study provides a theoretical foundation and a practical computational approach for accurately assessing the damage effects of non-standard explosive geometries.