Abstract In this study, an efficient time-domain prediction model is developed to predict unsteady flow vortex-induced vibrations (VIV) of flexible risers. The hydrodynamic forces on flexible risers are calculated on the basis of forced oscillation experiments on rigid cylinders. A period identification criterion, based on the spatial and temporal variations of reduced velocity, is proposed to divide the entire vibration process into exciting and damping periods of each exited mode. In exciting periods, assuming that VIV enters an ideal lock-in stage, a non-iterative solving model is established under modal space for response calculations, which efficiently predicts time domain VIV responses. In damping periods, free-decay vibration theory based recurrence formulas are established under modal space, and they get solved stepwise for modal responses. After some slight response adjustments to smooth period transitions, the VIV response time history can be obtained efficiently. This model is validated by steady flow VIV prediction cases, and further applied to predict oscillatory flow VIV experimental results. The prediction cases reveal that this model is able to realize high-speed VIV predictions with satisfactory results and no convergence problems. This model, with high efficiency and stability, is highly suitable for unsteady flow VIV prediction in engineering applications.

中文翻译：

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非定常流动下柔性立管涡激振动的有效时域预测模型

摘要 在这项研究中，开发了一种有效的时域预测模型来预测柔性立管的非定常流动涡激振动 (VIV)。柔性立管上的水动力是在刚性圆柱体受迫振荡实验的基础上计算的。提出了一种基于减速度空间和时间变化的周期识别准则，将整个振动过程划分为每个退出模式的激励和阻尼周期。在激励期，假设VIV进入理想锁定阶段，在模态空间下建立非迭代求解模型进行响应计算，有效预测时域VIV响应。在阻尼阶段，建立了模态空间下基于自由衰减振动理论的递推公式，并逐步求解模态响应。在对平滑周期过渡进行一些轻微的响应调整后，可以有效地获得 VIV 响应时间历史。该模型通过稳流VIV预测案例验证，并进一步应用于预测振荡流VIV实验结果。预测案例表明，该模型能够实现高速VIV预测，结果令人满意，没有收敛问题。该模型效率高、稳定性好，非常适合工程应用中的非定常流VIV预测。预测案例表明，该模型能够实现高速VIV预测，结果令人满意，没有收敛问题。该模型效率高、稳定性好，非常适合工程应用中的非定常流VIV预测。预测案例表明，该模型能够实现高速VIV预测，结果令人满意，没有收敛问题。该模型效率高、稳定性好，非常适合工程应用中的非定常流VIV预测。