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• A numerical model is developed to analyze underwater explosion of slender explosive and structure responses. • Slender explosive will generate a directional pressure field in the surrounding water. • The shape of explosive strongly influences shock wave dynamics in the near-field. • The direction effect of pressure and energy flux is significant. • The response of a plate subjected to near-field underwater explosion of a slender explosive is studied. The shape of a high-explosive is an important factor to consider in the near-field and contact explosion, but this has been rarely studied previously. In this paper, we first conduct experiments to study the directional effects of the underwater explosion shock wave of slender explosives. A numerical model based on the multi-material arbitrary Lagrangian Eulerian (MM–ALE) technique is then developed to study the influence of the explosive slender ratio on the generated shock waves. The numerical model is validated by experiment data. Then, tests are conducted with constant-mass cylindrical explosives with slender ratios ranging from 2.0 to 9.2. By comparing with the center-detonated spherical explosive, the peak pressure, pulse duration, impulse and energy flux of the underwater explosion of slender explosives are analyzed in detail. Furthermore, the effectiveness of the fluid-structure interaction algorithm is verified through the experimental data of a plate subjected to underwater contact explosion. Finally, the response of plates subjected to the underwater explosion of a slender explosive at different azimuths is studied. The interaction between the plate and the directional loads is analyzed. We conclude that the loads and structure responses of the near-field underwater explosion of slender explosives are different from those of spherical explosives. The analyses and results provide a reference for the near-field underwater explosion loads and structural response studies. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In order to understand the protective mechanism of helmet against shock wave, a head model under far-field blast is investigated experimentally and numerically. The distribution of overpressure on the surface of the head model are obtained and compared. The numerical simulations are carried out using the Multi-Material Arbitrary Lagrangian Eulerian (MM-ALE) technique with suitable material models for a Kevlar helmet and soft pads. The differences in the distributions of overpressure on the head models with and without the protection of the helmet are analyzed. The interaction of shock waves around the head and the helmet is investigated. Our experimental observations and numerical results indicate that, if protected by a helmet in the case of a shock wave acting from the front, the peaks of overpressure on the head are reduced at the top area, but increased at the rear area. The numerical simulations also show that the enhancement of the overpressure at the rear is mainly due to the collision of the shock wave. The underwash phenomenon also occurs when the shock wave acts from the side or the rear. [ABSTRACT FROM AUTHOR]