【作者】 石宏远；

【导师】 孙丽萍；

【作者基本信息】 哈尔滨工程大学 ， 港口、海岸及近海工程， 2009， 硕士

【摘要】 由于国际上海洋石油工业向深水推进,以立管为代表的海洋结构物的涡激振动问题重新受到人们的关注。海洋立管作为平台和海底进口之间的主要构件,同时也时比较容易损坏的构件。一定速度的海流和波浪流经立管时,会在其两侧形成交替脱落的旋涡,旋涡的脱落将对立管产生一个周期性的交变力,使得管道产生涡激振动,管道的振动反过来又对流场产生影响,使得旋涡增强。当旋涡脱落频率和立管自振频率接近时,旋涡的泄放将被结构的振动所控制,发生“锁频”现象,从而立管振动加剧,造成疲劳破坏。论文分析了一系列与圆柱体及海洋立管涡激振动有关的重要物理参数,利用数值模拟工具以及理论模型,合理地模拟了与圆柱体涡激振动相关的物理现象。论文的主要内容可以归纳为以下几个方面：1、利用CFD软件中动网格技术进行了数值试验,再现了受迫振动试验中圆柱绕流中旋涡脱落等物理现象,得到了工程中感兴趣的参数,如升力系数、曳力系数等,结果与试验值做比较,验证了CFD模型的正确性。建立了Ansys和CFX双向耦合模型,此模型能很好扩展成全三维或切片2.5维模型。2、提出了一种对升力系数向升力曲线转化的方法。采用Newmark时程分析法通过matlab编程对尾流振子模型中的方程进行求解,并按照Shear7软件中升力模型系数的定义做了计算,结果表明,尾流振子模型做为VIV经典经验模型,可以在给定一定经验值的条件下对Shear7或VIVANA等专业软件中默认的升力模型曲线做出修改。3、基于SHEAR7软件的立管疲劳分析。本文选悬链线立管为实例,在计算之前其转化为等效的直管,并将海流,管内拉力等作相应转换。并根据软件的输出数据,得到了立管的均方根位移、应力、疲劳损伤率等曲线,从而分析立管各部位受涡激振动影响的程度。最后根据DNV规范提供的S-N曲线公式可以对立管的疲劳寿命作简化计算。更多还原

【Abstract】 With the increased interest in worldwide deep-water petroleum production, more efforts have been put on the research activities on vortex-induced vibrations (VIV) during the past ten years.Marine risers,which are vulnerable to damage,are the main components to link upper platform and wellhead on the ocean floor. Nowadays they are being paid lots of attention because of the following reasons:as the flow over a riser within a certain Reynolds number regime, there are pairs of vortices shedding behind it alternately, there a fluctuant lift force is applied to it. From the view of fluid dynamics,the moving of riser changes the flow field around it, and then the lift force changes,so on and so forth. That is vortex induced vibration(VIV), a kind of fluid-structure interaction(FSI).VIV can bring fatigue breakage on risers for the periodical action.Main key parameters controlling the transverse VIV of circular cylinder and riser are discussed in detail. With numerical tool and proposed model in this thesis, the main characteristics of VIV of circular cylinders are interpreted.The main contents of this thesis are summarized as follows:1. In the use of CFD dynamic mesh model to carry out the numerical test,not only reproduce the physical phenomena of the forced oscillation tests, such as vortex shedding,but also access some interested parameters,such as lift and drag coefficients et al.They were compared with classic experiments to validate the CFD model primarily.The two-way fluid and structure coupling interaction model was established,which could be a good model to extend to the total three-dimensional model and 2.5 dimensional strip method in the future.2. Bring forward a method transforming the lift force coefficient to the lift curve, which was made into matlab program to solve the wake oscillator equation by Newmark time-use analysis.And did some calculation in accordance with the definition of the lift force model in Shear7,the results showed that given some value from the experience,the Wake oscillator model for VIV classic model could be used to modify the default lift curve model of some VIV software such as Shear7 and VIVANA.3. The fatigue analysis is done using SHEAR7 software. First the riser is equivalent to a straight pipe, together with the right current profile and the extension force. Some curves of curvatures of RMS displacement, stress and damage rate can be obtained. Finally the simplified calculation to estimate the riser’s fatigue life, according to the S-N curve is given by the rule of DNV.更多还原