【作者】 周巍伟；

【导师】 周力；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2009， 硕士

【摘要】 随着深海油气资源的逐步开发,海洋立管的应用由浅水区向深水区、极深水区发展。立管结构是连接平台和海底管道或井口的主要设备,受风浪流等环境载荷的作用,这些交变载荷对立管的疲劳寿命影响很大,所以疲劳是深海立管设计最主要考虑的问题。本文对钢质悬链线立管SCR(Steel Catenary Riser)载荷和疲劳寿命预测的方法进行了研究,着重研究了涡激振动对立管疲劳寿命的影响。首先对深海立管结构进行了介绍,重点介绍了悬链线立管和国内外在深海立管疲劳损伤方面的研究现状和进展。接下来对深海立管的波浪载荷进行了简要的阐述,然后重点介绍了流致立管振动的相关理论和计算方法,最后对利用模态方法分析立管涡激振动引起的疲劳损伤的理论进行了详细的阐述。将悬链线立管简化为忽略剪切力的索模型,对悬链线立管进行了模态分析,分析中考虑了流体附加质量的影响,得到其在海水中的频率和振型。根据斯托哈尔关系和外部流速大小的确定潜在的激励模态范围,并通过计算潜在模态的能量确定主要激励模态。根据能量平衡,求出升力系数和阻尼系数,从而可以计算出立管每阶模态下的模态力和模态阻尼。再利用模态叠加法对悬链线立管进行动力响应分析。然后根据Palmgren-Miner线性累积损伤准则并结合S-N曲线,分析了在不同流速下立管的涡激疲劳损伤。以2300mSpar平台的悬链线输油立管为例,计算了其在北海某流速作用下的疲劳损伤,得到了一些有意义的结论。最后讨论了某些参数对深海海洋平台SCR的涡激疲劳损伤的影响。悬链线立管采用索结构模型,进行动力学分析并利用模态叠加法对其进行动力响应分析。以工程中实际使用的1500m Spar海洋平台悬链线立管为例,分别就立管外不同来流速度、立管壁厚、内部流体密度和柔性接头刚度对立管疲劳损伤的影响进行了分析,得到了一些有意义的研究结果。更多还原

【Abstract】 As the exploitation of oil resources, the riser has been taken into practice in the deep sea region and even in the extra deep sea region. Riser is the connector between a platform and oil well in the seabed and will experience to the environment loadings as wind, wave and ocean current. The environment loadings are fluctuating, so they have the most significant effects on riser fatigue damage. This paper has studied the SCR(Steel Catenary Riser)’s loadings and fatigue damage, especially the VIV(Vortex Induced Vibration) induced fatigue damage.Deep sea SCR and wave loading is introduced at the beginning. Then the theory of flow-induced vibration is expounded. Finally, modal superposition method and VIV analysis method are introduced.The VIV induced fatigue damage is one of the most prime factors to affect the life time of SCR. The SCR is simplified into a cable model whose shear force is not considered. The modal analysis is carried out for the riser, and the added mass of the fluid is taken into account. The natural frequencies and the corresponding vibration modes are then obtained. The potential excited modes are determined by Strouhal number and flow velocity. And the main excited modes depends on their potential modal powers. According to balance of energy, the lift coefficient and damping coefficient are obtained. The riser’s VIV damage subject to different current is investigated by combining Palmgren-Miner liner cumulative rule and S-N curve. Furthermore, the dynamic response of the SCR is studied using modal superposition method. A 2300m Spar Platform-Riser system of engineering is studied.The fatigue damage of the offshore platform SCR induced by the short term current is discussed. For the fluid around the SCR, the vortex shedding frequency and the lift are considered. The SCR is modelled as a cable. The dynamic response of the SCR is studied using modal superposition method. A 1500m Spar Platform-Riser system of engineering is studied. And the SCR VIV induced fatigue damage is predicted. The effect of some parameters on the fatigue damage, such as inflow velocity toward the riser, riser wall thickness, fluid density inside the riser and the stiffness of flex joint, is studied. Some useful results are obtained for offshore engineering.更多还原