【作者】 雷凡；

【导师】 杨吉新；

【作者基本信息】 武汉理工大学 ， 公路桥梁与渡河工程， 2011， 博士

【摘要】 海洋结构物多在海洋环境中进行施工,具有极大的难度和特殊性。与陆地或浅水结构不同,海洋结构经常受到波浪、海流、地震等荷载的作用而产生有害振动。随着社会的发展,工程中新材料、新设备、新结构和新工艺的运用,结构不断向高、轻、大三个方向发展。特别是在海洋工程领域,随着海洋资源开发不断地向深海进军,越来越多海洋结构物转变为柔性结构。海底隧道、海洋平台等结构物由于自身刚度比较大,所以整体振动幅值不会很大,但海洋悬跨管道、深海采矿系统中的输送软管、水中悬浮隧道等结构则属于细长的柔性结构,容易在波浪、海流、地震等动力因素影响下产生较大的变形,并在部件内部产生额外的张力,极易引起结构的损伤甚至破坏。因此,深入开展水中柔性结构流固耦合振动特性以及在水流、地震等荷载作用下的力学行为的研究,对提高水中柔性结构的安全运营具有十分重要的理论和现实意义。本文针对水中柔性结构流固耦合振动特性以及在水流、地震等荷载作用下的力学行为进行研究。论文的主要内容如下：1、阐述了课题的研究背景和研究意义,对国内外流固耦合问题的相关理论以及在海流和地震作用下水中结构动力响应的相关研究进行了归纳和总结,阐述了水中柔性结构的振动特性以及在复杂水中环境荷载作用下的力学行为研究中尚待解决的问题。2、介绍了流体力学的基本概念和基本方程组,并对无粘性小扰动流动的基本方程和表达形式进行了论述,在此基础上,详细阐述了线性流固耦合系统有限元分析的位移-压力格式以及线性流固耦合系统的动力特性分析方法,最后给出了非线性流固耦合问题的ALE描述方法。3、为准确把握水中结构的动力特性,设计制作了水中悬跨结构、深水桥墩以及悬浮隧道的试验模型。分若干工况对各个模型在无水和有水环境下的动力特性进行了测试,并分析了不同尺寸、不同水位、不同形式对结构动力特性的影响。采用附加质量法以及三维数值有限元法对试验模型动力特性进行了计算,并对试验和计算结果进行了比较和分析。4、对柔性结构的静力行为进行了研究,总结了柔性结构在静载作用下的应力响应以及变形规律。分别采用附加质量法和三维数值有限元方法对两端固定约束的圆柱管道进行分析,通过比较有水、无水以及是否考预应力效应的计算结果,总结出水中柔性结构振动特点。并对水中柔性结构在简谐荷载作用下的响应规律进行了归纳。5、对水流作用下的圆柱绕流及涡激振动现象进行了介绍；基于标准k-s湍流模型,分别采用二维数值模拟和三维数值模拟的方法,对不同水流速度下的圆柱管道绕流流场的压力分布和速度分布进行分析,对海流作用下圆柱管道尾流区涡旋发展的过程进行了描述,探讨了水流作用下水中柔性结构动力响应规律。6、对结构地震响应的分析方法进行了介绍,并阐述了基于水动力模型的水中结构地震响应分析方法以及考虑流固耦合效应的水中结构地震响应数值有限元计算方法,建立了地震作用下水中柔性结构流固耦合效应分析模型,通过比较有水、无水以及是否考虑结构大变形的计算结果,探讨地震作用下水中柔性结构动力响应规律,并分析了结构长度、地震强度等因素对结构动力响应的影响。更多还原

【Abstract】 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 standardκ-εturbulent 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.更多还原