A Numerical Simulation Of Underwater Explosion Loads And Structure Response

Research on underwater explosion already has a history of over100years since the end of the nineteenth Century, but in China researchers began to attach importance to shock resistance of ships and shipboard equipment in the last ten years. Since the physical process of underwater explosion changes rapidly and is complicated, the damage mode diversifies according to different types of structures, distances, dosages and loads of variable time scales. It relates to the cutting-edges of scientific problems in many fields, so some mechanism of underwater explosion has been unknown. Underwater explosion loads include the shock wave, bubble pulse and cavitation effect. These loads own not only different time scales, but also the peak pressures with different orders of magnitude. Therefore, it is difficult to consider the influence of the loads on the structures and to analyze the different structural responses under different loads. Numerical study has become an important approach to study the phenomena of underwater explosion. The scholars at home and abroad investigated the problems based on various commercial software, but mainly concentrated on the dynamic response of structures under the shock wave loads because the ALE method of Ls-Dyna and the CEL method of Autodyn are accurate enough for shock wave loading calculation, yet it is hard for them to deal with the effect of bubble pulsating loads on structures. Generally speaking, only the two-dimensional bubble pulsation could be simulated without any structures, and very high quality of grids is required accompanying with rather low calculation efficiency. Thus compared to other commercial software, the built-in Geers-Hunter models coupled with the sound-structure method of Abaqus can tackle the shortcomings of other commercial software. Consequently, the dynamic response of structures under loads with different time scales could be computed accurately.First, in this study, the basic theories of Abaqus simulation of underwater explosion are described, then by the explicit solver and the implicit solver the shock wave and bubble loads are calculated. Secondly, given the bulk cavitation phenomenon may occur near the free surface predicted by the theoretical analysis, we simulated the phenomenon by Abaqus to validate the numerics. The computational results are in agreement with the experimental values. It illustrates the bulk cavitation effect cannot be ignored; Several air-backed plates subjected to underwater explosion are simulated through the acoustic-structure coupling. The finite element model of water and the scope of Geers-Hunter model are discussed. The local cavitation phenomenon and the influence of the bubble loads around structures are proved. Bubble loads may cause the much greater deformation of structures. Thirdly, through the analysis of shock resistance of the porous metal sandwich which is gradually popular in recent years, the advantage of metal foam sandwich is demonstrated. Finally, the dynamic response of a ship model subjected to underwater explosion is calculated and the influence of different loads on the structure is analyzed. The results could provide some reference for the whole ship anti-explosion performance analysis and design.