Dynamic response of offshore pipelines and risers under cross-flow (e.g. ocean currents, vessel motion etc.) has successfully been analysed. Although the pipelines are used for fluid transportation, sufficient attention has not been paid to the dynamic instability under axial flow. In this study, axial flow-induced instability mechanisms of offshore pipelines and risers are investigated. To this end, the interaction of the axial flow forces of a fluid element with the forces of the corresponding pipe element during pipeline flexural motion is analysed. Interpretation of the terms of the motion equation is provided and analogies with the model of dynamic buckling of a Euler beam are detected. Original transfer matrices are developed for the dynamic control of pipelines under axial flow. The critical values of the flow velocity causing dynamic instability and the corresponding axial flow-induced buckling modes are determined. Implementation of the method to a representative case study is provided and discussed.

中文翻译：

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海上管道和立管的动态失稳机制

已成功分析了横流（例如洋流、船舶运动等）下海上管道和立管的动态响应。尽管管道用于流体输送，但对轴流下的动态失稳问题尚未引起足够的重视。在这项研究中，研究了海上管道和立管的轴流引起的失稳机制。为此，分析了管道弯曲运动期间流体元件的轴向流动力与相应管道元件的力的相互作用。提供了运动方程项的解释，并检测了与欧拉梁动态屈曲模型的类比。原始传递矩阵是为轴流下管道的动态控制而开发的。确定了引起动态不稳定的流速的临界值和相应的轴向流动引起的屈曲模式。提供并讨论了该方法在代表性案例研究中的实施。