NUMERICAL SIMULATION OF TRANSIENT STRONGLY-NONLINEAR FLUID-STRUCTURE INTERACTION IN NEAR-FIELD UNDERWATER EXPLOSION BASED ON MESHLESS METHOD

Near-field underwater explosion involves transient and strongly nonlinear phenomena such as the mixing and coupling of multi-fluid flows, and the large deformation, damage and fracture of the structure. For the simulation of near-field underwater explosion, traditional mesh-based methods often face some difficulties, such as structural mesh distortion, low-accuracy in capturing multiphase interface and so on. In this regard, based on completely meshless methods, a transient strongly-nonlinear fluid-structure interaction numerical model is established for the whole Physical process of near-field underwater explosion including shock wave and bubble. The smooth particle hydrodynamics (SPH) based on Riemann solver is used for solving fluid dynamics, and the reproducing kernel particle method (RKPM) is adopted for structural dynamics. The fluid-structure interaction is realized by using the normal flux boundary condition. In order to improve the accuracy in solving the discontinuities of the flow field, the Riemann problem concept is introduced and combined with the MUSCL reconstruction algorithm. Aiming to solve the problem of accuracy decline caused by the drastic change of particle volume in the flow field, the adaptive particle splitting and merging algorithms are applied. To simulate the damage and fracture caused by underwater explosion, based on Lemaitre damage algorithm, the damage and fracture models for RKPM shell structure is proposed, and the crack initiation algorithm is developed according to the visual criterion. Based on the established SPH-RKPM model, the shock wave propagation, the bubble pulsation and jet, and structural damage in the near-field underwater explosion are simulated. The obtained fluid load and structural response are compared with the experimental data and other numerical solutions to verify the effectiveness and accuracy of the SPH-RKPM fluid-structure interaction model, and the underwater explosion load characteristics as well as the mechanism and law of the fluid-structure interaction structure damage are given. The present work aims to provide technical support for the load prediction of near-field underwater explosion, and to provide reference for the damage power assessment and warship protective structure design.