Comparison of the hydrodynamic ram caused by one and two projectiles impacting water-filled containers

•An experimental verified finite element model was used to examine the difference of hydrodynamic ram induced by one and two projectiles.•Two trace lines in the water were selected to extract the pressure distribution to study the non-linear superposition of the shock wave pressure and drag pressure.•The energy time histories of water and plates in these two cases with different impact energies were compared and analyzed. High-velocity impact on fluid-filled containers is a concern associated with the vulnerability of aircraft fuel tanks due to hydrodynamic ram (HRAM). The present study compared the hydrodynamic ram caused by one and two spherical projectiles impacting water-filled containers using a previously developed and validated numerical model. Two types of comparisons were conducted to study the difference in pressure distribution inside the water and energy-time history of various parts, respectively. The propagation velocity of the superimposed shock wave in the two-projectile cases is higher than the shock wave in the one-projectile cases. The change in the energy of the entry plate is not affected by the number of projectiles, while more of the energy from water is transferred to the exit plate in the two-projectile cases compared to the one-projectile cases.