深水钻井隔水管三维涡激振动理论模型

隔水管作为深水钻井的关键设备,国内外均对其涡激振动开展了大量的理论与实验研究,但都主要针对隔水管在横向的涡激振动,并没有考虑隔水管同时受到横向以及流向的耦合作用。为此,利用旋涡动力学理论,建立了同时考虑流向静态变形以及流向与横向耦合作用下的深水钻井隔水管三维涡激振动理论模型,采用有限单元法结合Newmark-β法对模型进行求解,并在深水试验池开展了相似实验对模型进行验证,编制了计算分析程序,模拟了不同海流流速下隔水管涡激振动模态以及三维空间形态,探索了三维空间下隔水管涡激振动响应机理。模拟结果表明:①随着表面流速的增大隔水管横向以及流向的振动模态分别增大,且流向振动模态阶次大于横向振动模态阶次,横向振动幅值远大于流向振动幅值;②隔水管流向的静态变形远大于流向涡激振动变形,流向的变形形态主要受静态变形的影响;③隔水管在横向以及流向涡激振动耦合作用下,空间形态变得扭曲,在进行隔水管组合配置设计时应该同时考虑来自横向和流向的影响。

The three-dimensional theoretical model for the vortex-induced vibration of deepwater drilling risers

For risers, the key equipment for deepwater drilling, many theoretical and experimental studies have been conducted on its vortex-induced vibration. However, these studies often focused on the lateral vibration, and did not consider the coupling effect of lateral and streamwise vibrations. Based on vortex dynamics theories, a 3D vortex-induced vibration theoretical model was built up for deepwater drilling risers under the coupling effect of streamwise and lateral vibrations together with streamwise static deformation. The model was solved by using the finite element method combined with the Newmark-β method. It was verified by similarity experiments in a deepwater experimental pool. After the calculation and analysis program was developed, the vibration modes and the three-dimensional space morphology under different current speeds were simulated to explore response mechanisms of the vortex-induced vibration of risers in three dimensions. It is shown that both lateral and streamwise vibration modes increase with the increasing of superficial flow velocity. The streamwise vibration mode is higher than the lateral vibration mode in order, but much lower in amplitude. The lateral static deformation is much larger than streamwise vortex-induced deformation, and the form of lateral deformation is mainly affected by static deformation. The riser becomes twisted in space under the coupling effect of lateral and streamwise vortex-induced vibration. So, it is necessary to take both effects into consideration when the riser system is designed.