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首页> 外文期刊>Arabian Journal for Science and Engineering >Nonlinear Dynamics of Three-Dimensional Prediction Model for a Flexible Riser Under Linearly Sheared Currents
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Nonlinear Dynamics of Three-Dimensional Prediction Model for a Flexible Riser Under Linearly Sheared Currents

机译：线性剪力作用下柔性立管三维预测模型的非线性动力学

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摘要

This paper presents a three-dimensional vortex-induced vibration prediction model for a long flexible riser under linearly sheared currents. Two distributed and coupled van der Pol wake oscillators are utilized to characterize the fluctuating lift and drag coefficients, respectively. It should be noted that geometric and hydrodynamic nonlinearities are also considered in our model. Numerical simulations by finite element method are carried out to solve the highly coupled nonlinear fluid-structure interaction equations. Firstly, modal analysis is performed to obtain the foremost ten natural frequencies of the flexible riser under top-end tension by theoretical and numerical methods, and the results agree very well. Then, nonlinear dynamic analyses are carried out to investigate the effects of linear shear flow on displacements, stresses, modal variations and phase portraits. The results obtained in uniform and linear shear currents are compared in detail. The results indicate that the asymmetric phenomenon along the riser span is more obvious with increasing linear shear velocity and the lock-in phenomenon of IL (in-line) response frequencies with multi-frequency is also observed along riser span. Moreover, it is also revealed that the dynamic responses simultaneously exhibit the standing and travelling wave patterns under linearly sheared currents, and the dynamic responses become more irregular than uniform flow.
机译：本文提出了在线性剪切电流作用下长挠性立管的三维涡激振动预测模型。利用两个分布式和耦合的范德波尔唤醒振荡器来分别表征波动的升力和阻力系数。应该注意的是，在我们的模型中还考虑了几何和流体动力学非线性。通过有限元方法进行了数值模拟，以求解高度耦合的非线性流固耦合方程。首先，通过理论和数值方法进行了模态分析，得到了顶端拉力作用下柔性立管的前十个固有频率，其结果吻合良好。然后，进行非线性动力学分析以研究线性剪切流对位移，应力，模态变化和相像的影响。详细比较了在均匀和线性剪切电流下获得的结果。结果表明，随着线性剪切速度的增加，沿立管跨度的不对称现象更加明显，并且沿立管跨度还观察到了IL（在线）响应频率与多频的锁定现象。此外，还揭示出，动态响应在线性剪切电流下同时表现出驻波和行进波型，并且动态响应变得比均匀流动更加不规则。

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