Abstract: Finite element simulation using LS-DYNA was performed to investigate the interaction of underwater planar shock wave and rigid quadrilateral structure. The characteristics of diffraction waves on both front and back surface of the rigid structure were analyzed and trace lines were gained. Vortex was formed near the corner of the structure diffracted by underwater shock with a void part of zero pressure existing in the local fluid region. Bulk cavitation near fluid-structure interface leads fluid pressure to drop to negative value, which is an important damage factor to merged structures. A derived pressure formulas of diffraction wave to rigid square structure is on the basis of simulation results and water's EOS. It is applicable to calculate diffraction pressure to underwater structure without affection of free water surface and deformation of the structure. It is helpful to the theoretical analysis of diffraction shock wave to underwater structure.

Key words: underwater explosion, planar shock wave, diffraction, numerical simulation