Top tension riser is one of the most frequently used and vulnerable equipment in deep-sea petroleum engineering. With experiments and CFD simulations, researchers have found some hysteresis phenomenon and bistable behavior in vortex-induced vibration of the cylinders. However, there is still insufficient research on the bifurcation phenomenon and the multi-stable behavior of the riser vortex-induced vibration. In this study, based on the Van der Pol wake oscillator model, the vortex-induced vibration cross-flow governing equations of the riser fluid structure–coupled system in linear shear flow are established. Then the simplified multi-degrees-of-freedom model with 15-order modes is derived by the Galerkin method. Poincare map is utilized to obtain bifurcation diagram and identify the dynamic property of the top tension riser in a wide flow velocity range. Nonlinear dynamic behavior such as bistable behavior and even tristable behavior are discovered from the bifurcation diagram. Combined with the riser coupled system’s eigen analysis and the three-dimensional spectrum contour, it is found that there are various phenomena of mode interaction in the riser system, including 1:3 internal resonance phenomenon. Such study can provide reference and guide the design and optimization of riser structural parameters.

中文翻译：

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剪切流中顶部张力冒口的涡激振动中的分叉现象和多稳态行为

顶部张力提升器是深海石油工程中最常用和最易损坏的设备之一。通过实验和CFD模拟，研究人员发现了由涡流引起的气缸振动中的一些滞后现象和双稳态行为。但是，关于立管涡旋引起的振动的分叉现象和多稳态行为的研究仍然不足。在这项研究中，基于Van der Pol尾波振荡器模型，建立了线性剪切流中立管流体结构耦合系统的涡激振动横流控制方程。然后通过Galerkin方法推导了简化的15阶多自由度模型。利用Poincare贴图获得分叉图，并在较大的流速范围内确定顶部张力提升器的动力特性。从分叉图中发现了非线性动态行为，例如双稳态行为甚至三稳态行为。结合立管耦合系统的本征分析和三维频谱轮廓，发现立管系统存在多种模式相互作用现象，包括1：3内部共振现象。该研究可为立管结构参数的设计和优化提供参考和指导。发现立管系统中存在多种模式相互作用的现象，包括1：3内部共振现象。该研究可为立管结构参数的设计和优化提供参考和指导。发现立管系统中存在多种模式相互作用的现象，包括1：3内部共振现象。该研究可为立管结构参数的设计和优化提供参考和指导。