Dynamic Response Research Of Submarine Flexible Structures With Fluid-Solid Interaction

Most submarine structures are constructed in the marine environment, which has great difficulty and particularity. It is different from the land structures that the action of wave, current and earthquake will make harmful vibrations of the submarine structures. With the development of society, and the application of new materials, new equipment, new structure and new technology, the structures are being higher, lighter and larger. Especially in the marine engineering field, nowadays, more ocean resources are found in deep sea, therefore people build more and more submarine flexible structures.The vibration amplitudes of the submarine tunnel and the ocean platform are not great because of the large stiffness of themselves. But the flexible and slender structures such as the free spanning submarine pipelines, flexible delivery hose and Submerged Floating Tunnel will have large deformation and stress under the action of wave, current and earthquake, which may cause structural damage. It is of great theoretical and practical significance to research the vibration characteristics with fluid-solid interaction and mechanical behavior under the action of current or earthquake, for improving the safe operation of submarine flexible structures.The vibration characteristics with fluid-solid interaction of submarine flexible structures and their mechanical behavior under the action of current or earthquake are studied in the paper. The main research contents are roughly as follows:1. The research background and the significance of this topic were elaborated. The correlation theory of fluid-solid interaction problems and relevant studies of dynamic response of submarine structures with the action of current and earthquake were summarized. Problems need to be solved in the research of vibration characteristics and mechanical behaviors with complicated environmental load of submarine flexible structures were discussed.2. The basic concept and equations of fluid mechanics were interduced. The basic equations and expression form of non-sticky small disturbance flow were discussed. The(ui,p) format of linear fluid-solid interaction system of finite element analysis and the analyze methods of dynamic characteristics were elaborated in detail. Finally, the ALE method of nolinear fluid-solid interaction problems was expounded.3. Submarine suspended span structure models, deep-water pier models and Submerged Floating Tunnel models were designed for experiments and analysis of dynamic characteristics of submarine structures. The experiments were used to test the dynamic characteristic of each model both in the air and in the water. The factors that influence the dynamic characteristics, including the structure size, water level and detailed form of structures, were analyzed. Additional mass method and three dimensional finite element method was used to calculate the dynamic characteristic of experimental models, the results of experiments and calculations were compared and discussed in the paper.4. The stress and deformation laws of flexible structures with dead load is studied and summarized in the paper. Both additional mass method and three dimensional finite element method was used to research the pipes with fixed ends. The vibration characteristics of submarine flexible structures were studied by comparison of calculation results of several conditions, including the structures in the air, structures in the water and structures with consideration of prestress. The paper also summarized the response of submarine flexible structures with the action of harmonic load.5. Flow around circular cylinder and vortex induced vibration phenomenon under the current was presented. Two dimensional and three dimensional finite element method based on standard?-?turbulent model was used to study the pressure and velocity distribution of flow field around pipe with different velocity of flow. The vortex development in the wake of the pipe was described in the paper, and the dynamic response laws of submarine flexible structures under the action of current were discussed.6. The main methods for earthquake response analysis of the structures were introduced. The research methods for earthquake response based on the model and the numerical finite element method with the consideration of fluid-solid interaction were expounded. The analysis model of submarine flexible structures with fluid-solid interaction and the action of earthquake was set up to study the dynamic response laws of structures in different conditions. The factors that influence the dynamic response of structures such as length of structures, of earthquake were also discussed in the paper.