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胡鹏基, 李朝玮, 刘秀全, 刘兆伟, 畅元江, 陈国明. 深水隔水管−水下井口耦合系统双向涡激振动特性. 力学学报, 2024, 56(3): 540-554. DOI: 10.6052/0459-1879-23-440
引用本文: 胡鹏基, 李朝玮, 刘秀全, 刘兆伟, 畅元江, 陈国明. 深水隔水管−水下井口耦合系统双向涡激振动特性. 力学学报, 2024, 56(3): 540-554. DOI: 10.6052/0459-1879-23-440
Hu Pengji, Li Chaowei, Liu Xiuquan, Liu Zhaowei, Chang Yuanjiang, Chen Guoming. Two-direction VIV characteristics of deepwater riser/wellhead coupling system. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(3): 540-554. DOI: 10.6052/0459-1879-23-440
Citation: Hu Pengji, Li Chaowei, Liu Xiuquan, Liu Zhaowei, Chang Yuanjiang, Chen Guoming. Two-direction VIV characteristics of deepwater riser/wellhead coupling system. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(3): 540-554. DOI: 10.6052/0459-1879-23-440

深水隔水管−水下井口耦合系统双向涡激振动特性

TWO-DIRECTION VIV CHARACTERISTICS OF DEEPWATER RISER/WELLHEAD COUPLING SYSTEM

  • 摘要: 深水隔水管−水下井口系统极易受外部海流影响产生涡激振动(VIV), 其VIV分析通常将底端水下井口简化为固支约束. 考虑水下井口下部非线性管−土耦合建立深水隔水管−水下井口耦合系统顺流(IL)及横流(CF)向VIV三维分析模型. 基于胡克定律将管−土相互作用产生的时变非线性土壤抗力转化为时变土壤等效刚度并与系统结构刚度叠加. 采用有限单元法进行分析模型离散, 采用Newmark-β法与4阶龙格库塔法进行VIV数值求解. 随后分别研究了管−土耦合作用及环境因素如海流流速、土壤硬度等对深水隔水管−水下井口系统CF及IL方向VIV特性的影响. 结果表明, 考虑管−土耦合的深水隔水管−水下井口系统约束弱化, 系统整体刚度减小, 固有频率降低, 深水隔水管−水下井口系统CF及IL方向的均方根(RMS)位移及振幅增大, 振动频率减小. 深水隔水管−水下井口系统VIV对土壤硬度的敏感度较低, 原因是系统结构刚度与土壤初始附加的等效刚度较大, 而土壤硬度变化额外附加的土壤等效刚度在系统总刚度中的占比较低.

     

    Abstract: Deepwater riser/wellhead system is particularly vulnerable by external current to vortex-induced vibration (VIV). The bottom end of the subsea wellhead is usually simplified as a clamped constraint in the VIV analysis of deepwater riser/wellhead system. A three-dimensional VIV analysis model of the deepwater riser/wellhead coupling system is established in the in-line (IL) and cross-flow (CF) directions in this paper. The VIV analysis model takes the nonlinear pipe-soil coupling under wellhead into consideration. The time-varying nonlinear soil resistance generated by pipe-soil interaction is transformed into the time-varying equivalent stiffness of soil based on Hooke’s law. The soil equivalent stiffness is superimposed with the structural stiffness of the riser/wellhead system. The VIV analysis model is discretized by finite element method, and VIV numerical solution is performed with Newmark-β method and fourth order Runge-Kutta method. The effects of pipe-soil coupling and environmental factors such as current velocity and soil hardness on VIV characteristics of the deepwater riser/wellhead system are subsequently studied. The results show that the constraint of the deepwater riser/wellhead system under the pipe-soil coupling is weakened, and the overall stiffness and natural frequency of the system are reduced. The root-mean-square (RMS) displacement and vibration amplitude of the deepwater riser/wellhead system in the CF and IL directions have an increase, while the vibration frequency decreases. The VIV of the deepwater riser/wellhead system has a low sensitivity to soil hardness, because the system structural stiffness and the initial additional equivalent stiffness of the soil are large, while the second additional equivalent stiffness due to the soil hardness changes accounts for a relatively low proportion of the total system stiffness.

     

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