Experimental and numerical study of the near-field underwater explosion of a circular plate coated by rigid polyurethane foam

Near-field underwater explosions can cause serious local damage to ship hulls. A protective shield sticking on the outer surface of a ship hull can effectively attenuate the shock loadings from these explosions. The present paper aims to experimentally and numerically analyze the anti-shock effects of a protective shield, which consists of rigid polyurethane foam (R–PUF) with certain thickness, and thin rubber skin, coated onto a circular plate in a near-field underwater explosion. The underwater explosion experiment was conducted in a man-made lake for both the bare and coated circular plates. The experimental results indicate that the protective shield can reduce the overall deformation of the circular plate by 41.1% on average under the experimental conditions. Then a Eulerian compressible fluid model is developed and used in combination with Abaqus/Explicit software in a numerical simulation to explore the anti-shock effects of protective shields. The overall deformation, velocity and displacement of the circular plate, and the pressure and velocity of the fluid are calculated. Comparisons between the experimental results and numerical simulations indicate that the developed compressible fluid model can effectively calculate the fluid response and the overall deformation of the circular plate effectively. The simulated results illustrate that the protective shield can effectively mitigate the peak value and the duration of pressure on the wetted surface in the initial stage. Then, two situations are considered to deeply investigate the shock mitigation effects of the protective shield. When the protective shield is kept unchanged while the detonation distance is changed (situation I), it was found that softer protective shields are needed for far detonation distance while stronger protective shields are needed for near detonation distance. Moreover, when the shock environment remains unchanged and the mechanical properties of the protective shield are changed (situation II), it was found that the protective shield should be as soft as possible to generate a sufficient energy absorption capacity. These research results are useful in protective shield design for ship hulls subjected to near-field underwater explosions.