NUMERICAL STUDY OF UNDERWATER IMPLOSION OF SPHERICAL PRESSURE HULL ON DEEP-SEA SUBMERSIBLES

The failure of the pressure hull is the key subsystem of underwater vehicles, and seriously threatens the vitality of the whole underwater vehicle. Moreover, the shock waves from underwater implosions of failure pressure hull will cause deformation and even collapse to the adjacent structures, which is detrimental to the vehicles such as underwater robots and manned deep submersible vehicles working in the deep sea environment. In this work, the open-source solver OpenRadioss is adopted to conduct the numerical analysis of the spherical pressure hull within the shock waves of the underwater implosion and structure deformation and failure. The compressible multiphase flow is simulated by the arbitrary Lagrange-Euler method with multi-physical materials and the structures are described by constitutive models of brittleness and metal ductility, respectively. Firstly, the underwater implosion of a thin-glass sphere is simulated. The pressure of shock waves is compared with the experiment to verify the accuracy of the numerical method. Secondly, the dynamic response of the spherical hollow ceramic pressure hulls with internal perfect gas is investigated accordingly to reveal the fluid- structure coupling effects of underwater implosion induced by the failure of brittle materials, where the structure no longer bears any pressure after failure. Finally, the underwater implosion under the same environment pressure is simulated based on the Johnson-Cook plasticity and failure model. The implosion characteristics in the failure process of metal pressure hulls are summarized by analyzing the coupling pressure, structural deformation and damage, and energy evolution, respectively. Moreover, the differences between the hollow brittle ceramic sphere and ductile titanium alloy sphere in the process of underwater implosion are discussed. The influence of fluid-structure interaction and the mechanism without different materials are analyzed for the spherical pressure hull, which provides a basis for the design and material selection of the pressure support structure of the underwater vehicle.