Fluid - Structure Coupled Numerical Method And Its Applications

The interaction of fluid flow and flexible solid structures is frequently encountered in many areas of civil, mechanical, marine, aerospace, chemical and nuclear power engineering. As one of those interaction problems, nonlinear dynamic fluid-structure interaction has become one of the most challenging research issues in academic and engineering field at present. With the development of computational resource and fluid-structure computational methodologies, how to adapt modern numerical method to deeply study the influence of structure vibration on fluid flied is of great significance to avoid the fluid-induced resonance and improve the reliability and security of the structures. In this thesis, a weak dynamic nonlinear fluid structure interaction staggered numerical simulation method is put forward and established, and is verified by several real examples through general-purpose finite element program MARC and FLUENT. The main works of this thesis are listed as follows:1. For the structure region of the fluid-structure interaction system, the incremental nonlinear finite element model is introduced based on large geometric deformation. Meanwhile, it is applied in the vibration problem of a flexible cantilever beam to discuss the effect of non-follow force model and follow force model to the structure responses.2. For the fluid region of the fluid-structure interaction system, the N-S equations with Arbitrary Lagarian-Eulerian(ALE) description are adopted to exactly describe the fluid boundary movement of FSI system. Also, the dynamic mesh method is introduced to maintain good element shapes of the fluid. Then, taking the fish-like swimming foils as a calculation example, the validity of ALE method and dynamic mesh method is verified.3. Through the compatible conditions on the boundary between the fluid and structure, a weak coupled nonlinear dynamic fluid-structure interaction model is set up. In this model, the solid region is solved with code MARC, while the fluid region is simulated with code FLUENT. To realize the data transmission between the two softwares, the user defined functions of both softwares are developed and compiled. At the same time, the data transmission methods of movements and loads between the non-matching discrete meshes of fluid and structure on the interaction surfaces are given.4. As the application of methods and models mentioned above, firstly, the elastic-mounted square rectangular free oscillation problem is present. The results show that, when oscillation frequencies of the rectangular are in a certain range, the "lock-in" phenomenon, a kind of nonlinear fluid-structure interaction resonance phenomenon, and "beat" phenomenon will appear. Secondly, the flow-induced vibration problem of a flexible cantilever beam is analyzed in details. And the effects of staggered coupled time step sizes, structure nonlinear finite element models and Renault number to the responses of the cantilever beam are investigated respectively.