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Fluid filled structure widely exists in the field of ship and ocean engineering, but the investigation concerned with the whipping response of a fluid filled structure subjected to an underwater explosion is very less. A numerical model considering the effect of an internal fluid is established in this paper. In the implementation of the numerical model, the doubly asymptotic approximation for the external fluid is used to model the external fluid domain, the doubly asymptotic approximation for the internal fluid is used to model the internal fluid domain, and the dynamic response of the structure is simulated by the finite element method. After that, the numerical model is validated against the analytical solution. The numerical result agrees well with the analytical result. Finally, the whipping response of a fluid filled cylindrical shell subjected to an underwater explosion is investigated and the influence of the internal fluid on the whipping response is analyzed. The main results are as follows. The existence of the internal fluid makes the maximum relative displacement decrease, as the density of the internal fluid and the sound speed within the internal fluid increase, the maximum of the maximum relative displacement decreases. [ABSTRACT FROM AUTHOR]

The damage process of ship structures subjected to underwater contact explosions is characterized by strong nonlinearity, thus there are great challenges in solving such problems. Firstly, the full Smoothed Particle Hydrodynamics (SPH) method for the fluid and structure interaction (FSI) is established based on compressible SPH fluid dynamics and SPH shell. Furthermore, the normal flux method is introduced to treat the interface. However, given the immaturity of the SPH shell in dealing with the fracture of complex structures, an SPH-FEM (Finite Element Method) coupling method for FSI is proposed with the “glue” treatment applied at the interface. The above two methods are verified by an underwater contact explosion experiment. Afterwards, the pressure-time relationship within six charge radii is fitted based on the axisymmetric SPH simulation. On this basis, the flat plates subjected to underwater contact explosions are studied in detail with the application of a combined damage variable. Three stages in the damage process, namely localized bulging, discing and petaling, are observed, and the crack and deflection are found to be sensitive to the changes of peak pressure and impulse respectively. Finally, complex models of a stiffened plate and a ship are established to further study the damage characteristics. [ABSTRACT FROM AUTHOR]