【作者】 任大朋；

【导师】 黄一；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2006， 硕士

【摘要】 在一定的特征海流作用下，具有较低阶固有频率的深水立管极易发生涡激振动，如何对这种现象进行准确预报一直是一个难题。本文结合计算流体力学方法和结构有限元方法，构造了一种用于分析该现象的迭代算法。在迭代过程中，通过对结构进行有限元分析获得立管的振动，并借助于动网格技术将立管的振动效应定义为流体区域中的立管运动，然后应用计算流体力学方法分析由涡激振动引起的流体载荷。 本文考虑了均匀流和剪切流两种海流状况下的涡激振动并通过相关文献中的实验数据对计算方法进行了验证。分析结果表明，立管的运动加强了旋涡的释放；随着迭代次数的增加，存在于涡激振动中的流固耦合效应可以被该方法较好地模拟。通过计算，可以验证作用在立管上的升力周期是阻力的2倍。尽管阻力峰值比升力稍大，但升力的变化幅度约是阻力的10倍。本文认为，在立管的设计过程中，既要考虑垂直于来流方向的升力，也要考虑平行于来流方向的阻力。 为了减轻涡激振动带来的危害，本文又对涡激振动抑制装置整流罩进行了研究。计算结果显示，在整流罩的作用下，涡激振动的程度大大降低。本文分析了一系列不同的整流罩布置方式并与光管计算结果加以比较。 在计算过程中，分别采用流体分析软件FLUENT分析流场和有限元分析软件ANSYS计算立管的动力响应。更多还原

【Abstract】 The vortex-induced vibration (VIV) of a deepwater riser may occur when the long riser with lower natural frequency encounters certain sea current, but the prediction of such phenomenon is always a difficult problem in deepwater riser design. In this thesis, an iteration method between CFD analysis and structural FE analysis is proposed. In the iteration process, the vibration of the riser obtained through structure FE analysis is applied to define the riser wall movement in the flow field by dynamic meshing technique and fluid forces caused by the vortex shedding are calculated in CFD analysis.Both uniform flow and shear flow are studied in this thesis and the process is verified according to some experiment data from relevant literature. The analysis results indicate that the riser’s movement enhances the vortex’s shedding, and the fluid-structure coupling state in the VIV phenomenon can be simulated under certain accuracy which depends on the iteration times. Through the calculation, it can be validated that the period of lift force is about twice of the drag force. Though the peak value of drag force is a little higher than lift force, the amplitude of lift force is about 10 times of drag force. This thesis concludes that both cross-flow vibration and in-line vibration should be considered in the deepwater riser design process.In order to suppress VIV, the effect of a shedding-suppression device called riser fairing is also studied. Calculations indicate that the intensity of vortex shedding is destroyed greatly. Arrangements of fairing are also studied and the suppression effects are embodied by comparison to the analysis results of the bare riser.CFD software FLUENT is used to analyze the fluid field and FE software ANSYS to analyze the riser dynamic response.更多还原