【作者】 孙士丽；

【导师】 姚熊亮；

【作者基本信息】 哈尔滨工程大学 ， 船舶与海洋结构物设计制造， 2011， 博士

【摘要】 高频流固耦合现象的成因很多,如水中航行体受到瞬态载荷的冲击作用,水中航行体的突然启动或突然停止,物体自由落入水中,产生砰击。这些是比较常见的高频流固耦合现象。还有一些高频流固耦合现象并不常见,但和一般高频流固耦合问题却有相似的机理,如导弹离开发射筒时,产生强烈砰击,可诱发高频流固耦合现象,弹体出水时,载荷变化可诱发高频流固耦合问题。有些高频流固耦合问题还会伴随自由液面效应,如结构的出水问题或入水问题。在发生高频流固耦合问题时,水中航行体还可能同时受到环境载荷的作用,如波浪、洋流等。本文研究的范围是自由液面附近水中高速航行体的高频流固耦合问题,以弹体出入水问题为例。本文从弹体运动的基本现象入手,重点研究弹体出入水时的流固耦合效应、自由液面效应、砰击现象、环境载荷等,旨在揭示弹体出入水时的流固耦合动力学特性。首先,本文从实验技术、数值方法等方面回顾了国内外关于弹体出入水相关问题的研究进展情况。介绍了弹体出入水问题涉及的基本现象,包括流固耦合现象、水冢现象、入水砰击现象、波浪中出水等。重点综述了国内外流固耦合数值计算方法的研究进展。在上述基础上提出一些尚需进一步解决的问题,为指导本文的后续工作奠定基础。弹体属于航行态结构同时伴随高频的弹性振动,其流固耦合问题也因其运动特性表现出特殊性。因此,选取合适的流固耦合方法研究弹体流固耦合问题至关重要。本文根据弹体的运动特性,在二阶双渐近法(DAA2)的基础上,提出一种将运动非线性引入到双渐近法计算的一种流固耦合数值计算方法。由于它考虑了运动非线性,本文暂且称其为非线性双渐近法(NDAA)。该方法是一种考虑部分非线性的混合方法。同时,以球壳为例,研究运动非线性对水中结构高频流固耦合动态特性的影响,给出运动非线性不能忽略的边值条件。弹体出水时,弹体的向上运动会使自由液面产生水冢,其载荷特征也会发生变化。本文建立了推导一种考虑自由液面效应的NDAA方法,在研究可压缩性对动量方程及连续性方程影响的基础上,对NDAA数学模型的控制方程与自由面边界条件的相容性进行分析和论证。在对数学模型进行可行性分析的前提下,采用该数学模型分析自由液面附近结构出水时的水冢现象,载荷特征及其出水机理,并对自由液面附近结构运动进行研究。弹体属弹塑性结构,在其出水过程中会伴随弹性振动。因此,本文推导一种适用于高频流固耦合计算的NDAA方法,以弹体突然启动问题为例,分析高频流固耦合现象的特征。与不考虑可压缩性的理论解进行比较,分析可压缩性在高频流固耦合问题中的影响及高频流固耦合现象的产生机理；与考虑可压缩的估算值进行比较,证实本文NDAA数学模型在计算高频流固耦合问题时的合理性。并给出影响高频流固耦合现象的因素。环境载荷是影响弹体出水的关键因素,尤其是波浪载荷。本文将波浪载荷引入弹体出水流固耦合的数值计算,以平面进行波为例,开发考虑波浪载荷与结构弹性振动耦合的动力学模型,重点模拟弹体在波浪中出水时波面形状变化以及弹体穿透波面的过程。同时研究波浪参数(波高、周期)对弹体出水姿态的影响。建立了三维弹性结构入水冲击流固耦合数学模型,采用该法模拟三维柱体自由落水时自由液面变化情况以及柱体运动情况,研究入水砰击力的特征。在对该法可行性及优越性分析的前提下,采用该法模拟面接触入水砰击问题,分析可压缩性对面接触入水冲击问题的影响,比较弹性体入水与刚体入水的差异,分析弹性体刚度对入水冲击力的影响。最后给出适合弹体入水砰击力的解析表达式,方便用于弹体入水砰击力的计算。给出回转体刚弹耦合数学模型,在对该数学模型进行验证的前提下,利用该模型分析潜艇的刚体运动及弹性振动。并根据弹体出筒过程的受力特点,研究潜艇刚体运动对弹体流固耦合运动及受力的影响。更多还原

【Abstract】 There are many reasons for the happening of the high frequency fluid structure interaction phenomenon. For example, the underwater moving structure is subjected to the transient load, and the underwater structure suddenly begins moving or stops moving, and the structure drops into water freely. These are all common high-frequency fluid structure interaction phenomenon. And there are some other high-frequency fluid structure interaction phenomenon not often seen. But they have the similar mechanism with the common ones. For example, the missile leaves the launch tube and the intense impact happens leading the high frequency fluid structure phenomenon, or the missile goes out of water and the load on the missile changes rapidly leading to the high frequency fluid structure phenomenon. Some high frequency fluid structure problems may be accompanied with the free surface effect sunch as the structure going out of or entering into water. When the high frequency fluid structure interaction phenomenon happen, the underwater moving structure may be subjected to invironmental loads such as the wave or the ocean current simultaneously. The scope of the research in the paper is about high frequency fluid structure interaction phenomenon of the high speed structure near the free surface. The problems about the missile going out of and entering into the water are taken as example.In the paper it emphatically researches on the effect of the fluid structure interaction, the free surface, the slamming, and the environmental loads based on the basic law of the movement of the missile to give out the hydrodynamic characteristics of the missile which interacts with the free surface while going out of water.Firstly, the development of the missile going out of water and related problems are reviewed from the aspects of the experiment techniques and the numerical methods. It introduces the basic phenomenon involved with the missile going out of the water, including the fluid structure interactions, the spikes, the slamming, going out of water in wave and so on. It emphatically summarizes the development of the numerical simulation methods of the fluid structure problems. And it reviews and discusses the developing process and the applicability of the numerical methods about the fluid structure interaction problems. At last, the slamming phenomenon of the water entry problems and the movements of underwater structures in wave are summarized. On the basis of the above, it puts forward some problems unresolved presently to give the instructions for the late researches in the paper.The missile is the kind of the structures which navigate in water accompanying high-frequency elastic vibration. Its fluid structure interaction problems behave special characteristics. So, it’s very important choosing proper methods to research on the coupling problems between the missile and the water. In the paper, it puts forward a fluid structure interaction method which introduces non-linearity of the missile movement into the DAA calculation according to the movement characteristics of the missile on the basis of the DAA2 method. The method is called NDAA for the moment because it considers non-linearity of the missile movement. The method is a kind of blending techniques considering partial non-linearity. In the meanwhile, the influence of non-linearity of movement on the dynamic behavior of the coupling movement between the missile and the water is studied taking an elastic sphere as an example to give the boundary condition for non-linearity not neglectable.The upwards movement of the missile can make free surface emerging spike while the missile going out of water and the load characteristics will change simultaneously. In the paper it builds the NDAA model considering the free surface effect. The influence of the compressibility on the momentum equation and the continuity equation is studied to analyze the consistency of the governing equation and the free surface boundary condition of the NDAA model. On the basis of the feasibility analysis, the spike phenomenon, the load characteristics and the mechanics of going out of water are analyzed using the model. At last, the movement of the missile going out of water is researched.The missile is elastic-plastic and the elastic vibration will accompany the missile’s upwards move. So, in the paper it develops a kind of fluid structure interaction method called the NDAA model which adapts to the high frequency fluid structure interaction calculations. The missile suddenly moving is taken as an example to analyze the characteristics of the high frequency fluid structure phenomenon using the NDAA method. And the method is compared with the theoretical result without considering the compressibility to analyze the influence of the compressibility on the high frequency fluid structure interaction problems and the mechanisms of the happening of the high frequency phenomenon. The method is compared with the estimated result considering the compressibility to validate the rationality of the NDAA model. And the influencing factor for the calculation of the high frequency fluid structure interaction is also given.The environmental loads are the critical factors influencing the attitude of the missile, especially for the wave load. In the paper, the wave load is considered into the numerical calculation. The plane wave is taken as example to explore the coupling dynamic model between the wave load and the structure’s elastic vibration and mainly simulate the change of the wave surface while the missile piercing through the water. In the meanwhile, the influence of the wave height and wave period on the attitude of the missile is researched. The fluid structure numerical model for the three-dimensional elastic structure entering into water is built to simulate the movement of the free surface while the cylinder dropping into water freely and the characteristics of the slamming force is researched. On the basis of the feasibility analysis and superiority analysis, the face-contact water entry problems are simulated using the method to analyze the influence of compressibility, compare the difference of the elastic body and the rigid body and analyze the influence of stiffness on the slamming force. At last, the semi-analytical result for the slamming force of the missile dropping into water is given to conveniently calculate the water entry problems of the missile.The numerical model for the coupling of the rigid movement and the elastic vibration of the revolving body is given. The numerical model is validated to analyze the rigid movement and the elastic vibration of the submarine. And according to the load characteristics of the missile going out of the launch tube, the influence of the rigid movement of the submarine on the missile’s movement and load is studied.更多还原