Numerical Methods For Compressible Multi-fluid Flows And Their Applications In Underwater Explosion

Systems with multi-fluid flows involve various multi-medium interactions,like liquid-liquid,gas-liquid and fluid-solid interactions.Research on compressible multi-fluid flows are critical in various fields which cover inertial confinement fusion,rocket engine,bubble flow,underwater explosion,and many others.As the computer science develops greatly,numerical simulation has become a powerful research tool and development of the numerical simulation technology for compressible multi-fluid flows has important practical engineering significance.In the context of the national marine strategy and with the development of underwater weapons,the role of underwater explosion in the military field will be more prominent.This dissertation is concerned with the numerical methods for compressible multi-fluid flows,and its application to underwater explosions.The main work of the dissertation can be summarized as follows:Based on the Modified Ghost Fluid Method(MGFM)and Modified Ghost Solid Method(MGSM),the Modified Ghost Method(MGM)is proposed to deal with the combined compressible multi-fluid multi-solid interactions with elastic solid.Using MGM,a coherent and consistent approach is constructed to simulate truly compressible multimedium problems involving gas,liquid and solid.Consistency indicates that essentially the same approach of solving the Riemann problem applicable at the interface to arrive at the ghost cell properties for use in the respective media(whether solid,liquid or gas)is used at different interfaces.Furthermore,the above-mentioned method is generalized so that it can be used to simulate compressible multi-medium interaction with elastic-plastic solid and then is applied to study the interaction between elstic-plastic soid structure and the underwater explosion.The response of complex solid structures under underwater explosion is studied.The numerical experiments verify the viability,effectiveness and versatility of the proposed method which is able to accurately predict the wave pattern at various interfaces.The 5-equation model with anti-dissipative interface sharpening effect is derived.Model of underwater explosion bubble dynamics for ideal explosives is established.The fluid components are modeled by Mie-Grüneisen EOS which is referred to as general or complex EOS.MUSCL-Hancock scheme is extended to construct input states for Riemann problems,whose solutions are calculated using generalized HLLC approximate Riemann solver.Then,the numerical method for underwater explosion bubble dynamics for ideal explosives is proposed.Based on the finite volume method,using the proposed numerical method and model for underwater explosion bubble dynamics for ideal explosives,a hydrodynamic program is developed.Adaptive mesh refinement(AMR)capability and the MPI parallelization are built into the hydrodynamic code by virtue of Paramesh library.Numerical experiments verify the effectiveness and auuracy of the proposed model and numerical method.Based on the model of underwater explosion bubble dynamics for ideal explosives,with Miller's Extension accountting for the late energy release process for the non-ideal explosives,model of underwater explosion bubble dynamics for non-ideal explosives is established.The corresponding numerical method for underwater explosion bubble dynamics for non-ideal explosives is proposed to study the kinetics of secondary reactions for underwater explosion of non-ideal explosives.The pool underwater explosion experiment for non-ideal explosives is carried out.The numerical simulation results agree well with the experimental results which validates the model and proposed numerical method for underwater explosion bubble dynamics for non-ideal explosives.