Research On The Impulsive Load Of Underwater Explosion Using Smoothed Particle Hydrodynamics

As the background of near-field underwater explosions of warships, near-field and near-boundary underwater explosions are studied in this paper. The two problems involve some special features, such as large deformations, moving material interfaces, interaction between shock wave and the deformable boundary, free surfaces, etc. Mesh distortion will occur when the conventional grid-based methods are used to solve the previous problems, and it maybe lead to the calculation breakdown. While, the smoothed particle hydrodynamics (SPH) method is a numerical simulation method with adaptive, meshfree, particle and Lagrangian nature. It avoids mesh deformation and is very suitable to solve problems with large deformations and the impact loads. All of these characteristics lay the foundation for simulating underwater explosions.Based on examined in depth of the basic theory of SPH method and underwater explosion, two-dimensional numerical model of underwater explosion is built using SPH method. SPH program package is compiled to calculate the load strength of shock wave and the higher accuracy of results is obtained. And it proves the accuracy of the calculation on underwater explosion using SPH method. The influences of different parameters on shock load of underwater explosion are also studied in the paper. Next, near-boundary underwater explosion is investigated, including the numerical emulation of mines lying on the seabed, the bubble pulsation under the influence of complicated boundary and the phenomenon of spike of free surface. It exactly reshows the reflection and transmission of the shock wave on the interface, and provides valuable reference for the research on the mechanics of the interaction between the shock wave and the boundary. In the end, the traditional SPH method is improved to form CSPH and GSPH methods. Three SPH methods are applied to the research of issues about the shock tube and detonation process. The calculation results of these three methods are analyzed and compared in the paper. It shows that the corrected SPH methods are also suitable for the solution of the problem about shock wave. And the accuracy is improved and the numerical fluctuation is also reduced.SPH method is successfully applied to the numerical simulation of the underwater explosion in this work. The propagation law of the underwater shock wave and the mechanism of the interaction between the shock wave and the boundary are disclosed. It provides a new numerical research technique for the problem of underwater explosion and a precise model of shock wave load, and also provides a theoretical basis for the protective design of ship structures.