Finite Element Method In Fluid-Structure Coupled System

The fluid-structure coupled systems for compressible fluids with visco-damping and structures with Rayleigh damping have been studied in this dissertation. The fundamental problems for fluid-structure coupled systems have been classified and discussed. After comparing and analyzing three basic finite element formulation of the coupled systems, the author points out their advantages and shortcomings, then the displacement-based finite element method has been investigated. The method seems to be suitable for coupled systems.Author has given three methods of connecting interfaces such as Programming Direct Connecting Method, Penalt Function Element Method and Mixed Element Method which could perform the fluid-structure interface connection effectively. Preconditioned Lanczos Algorithm is proposed to emhance the convergence of solution of ill-conditioned linear equations which may occur in coupled systems. By the principle of penalt function, the irrotational fluid field is constrained, and author has proposed the Difference Method for distinguishing fluid vortex modes among the natural modes of coupled systems. Author has calculated the real frequencies with the extra deductive method, and discussed the influence of the numerical solution due to the irrotational constraint.Through analyzing the characteristic of the fluid displacement element, author has found that some present elements had the defect of modeling fluid deformance improperly which led to the pseudo deformable energy in the fluid field , gives twoovercoming approaches -- improving the elementalinterpolation function and employing reduced/selective integration in the elemental computation. An improved four-node...