A Study Of Several Issues In The 3D Multi-material ALE Method And Its Applications

The simulation of the multi-material flow is very important for both theoretical research and engineering pratice.However it is a challenge issue in the computational mechanics because it involves complicated problems such as the interface reconstruction and the multi-material advection.Based on the Multi-Material Arbitrary Lagrangian Eulerian(MMLAE)method,the key techniques are studied to improve its accuracy,efficiency and the robustness.Moreover,the MMALE method is also coupled with the Finite Element Method and the Material Point Method to simulate the complicated fluid solid interaction problems.The main contents of this thesis are described as follow:1.The mathematical properties of the Moment of Fluid method(MoF)is studied.The analytical derivatives of its objective function deduced for both 2D and 3D implementations and the discontinuity of the high order derivatives is also detected and studied.The efficiency and the robustness are improved significantly by using the analytical derivatives.Moreover,The geometry essence of the volume conservation equation is also studied and the predicted Newton's method is proposed which improves the efficiency for solving the volume conservation equation significantly.2.The “Clipping and Projecting” method is proposed to calculate the intersection of two arbitrary polyhedrons which solves the most important technique in the 3D multimaterial remapping.The efficiency and robustnss of the “Clipping and Capping” method is significantly higher than the former algorithms.3.The coupled MMALE-FEM method is proposed to simulated the complicated fluid solid interaction problems and it successfully simulates the complex CONT test which involves multi-material,strong shock wave propagation and fluid solid interaction.4.The coupled MMALE-MPM method is also proposed to simulated the complicated fluid solid interaction problems.The coupled MMALE-FEM method preserves the advantages of the MMALE and the MPM method for fluid and solid simulation respectively.In pratice,the coupled MMALE-MPM method simulates the interaction between the air blast and the RHA plate successfully.