Numerical simulation and analysis of the chain-reaction implosions of multi-spherical hollow ceramic pressure hulls in deep-sea environment

Thin-walled hollow ceramic pressure hulls on deep-sea underwater vehicles are at risk for highly destructive chain-reaction implosions. A numerical method of simulating the chain-reaction implosions of multiple ceramic pressure hulls in deep-sea environment was developed. The fluid solver used for this method adopted the compressible multiphase flow model and adaptive mesh refinement, combining the finite element method and the failure criteria of brittle materials to determine the conditions that trigger an implosion. An implosion experiment was conducted for a single ceramic pressure hull, and the experimental results verified the accuracy of the fluid solver based on compressible multiphase flow theory. The chain-reaction implosions of two ceramic pressure hulls were also computed. The computation results showed that the air cavity in a spherical pressure hull diffused the expansion wave during the compression stage. The pressure drop in the flow field initiated by the expansion wave caused the ceramic spherical shell to reach its ultimate strength, thus triggering chainreaction implosions. The two implosion shockwaves were superimposed during the diffusion process. The peak pressure at the superposition position of the two shockwaves is related to the spacing between the two pressure hulls.