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<p>As critical drilling equipment, deepwater drilling riser system comprises multiple integrated components which exhibit natural vibration modes characterized by low frequency and high density. The vibrational response of these structures in actual marine environments is highly complex. Internal solitary wave (ISW), a typical nonlinear wave phenomenon in the ocean, generates sudden strong shear currents that can significantly excite multi-mode and nonlinear vortex-induced vibrations (VIV) in risers. To reveal the transient nonlinear VIV responses of the deepwater drilling riser system under ISW, this study establishes a semi-empirical nonlinear fluid–structure interaction model. A nonlinear dynamic model of a riser system based on actual engineering configurations, considering both the geometric nonlinearity of the riser system and the nonlinearity of the soil. It couples the modified Van der Pol wake oscillator model. The ISW-induced velocity profile is used as the input to the dynamic model, and the structural dynamics are solved using the finite element method. The study reveals that ISW suppresses cross-flow (CF) vibration while amplifying in-line (IL) displacement, inducing significant bending moment responses near pycnocline. The riser vibration undergoes a mode-switching evolution from an ordered state to a disordered state and finally back to an ordered state in the temporal dimension. The energy distribution of the riser vibration exhibits spatial non-uniformity, reflecting a mode competition phenomenon. Moreover, during the strengthening phase of the ISW, the riser vibration shows continuous peaks, demonstrating an obvious multi-frequency phenomenon. The 2D phase portrait shows that the trajectory evolves from multiple non-overlapping irregular elliptical rings at the initial stage of the ISW to chaotic points near its maximum amplitude and finally reverts to irregular elliptical rings as the wave decays. The 3D phase portrait shows that the riser vibration trajectory appears as a tornado-like shape spiraling upward along the IL direction. Increasing the ISW amplitude or the current velocity significantly increases the extreme IL displacement in the deep layer. Increasing the top tension effectively increases the equivalent stiffness and natural frequency of the riser system, suppresses the nonlinear large-displacement response induced by ISW, and thereby prolongs the fatigue life of the structure.</p>

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Nonlinear vortex-induced vibrations of a deepwater drilling riser system under ISW

  • 期刊论文

  • 发表日期：

    2026年7月29日

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  • Na Qiu,
  • Fufeng Xue,
  • Jianguo Wang,
  • Yanzhe Wang,
  • Lin Chang,
  • Cong Zhang,
  • Xiuquan Liu,
  • Yuanjiang Chang,
  • Yongbo Zhang

摘要

As critical drilling equipment, deepwater drilling riser system comprises multiple integrated components which exhibit natural vibration modes characterized by low frequency and high density. The vibrational response of these structures in actual marine environments is highly complex. Internal solitary wave (ISW), a typical nonlinear wave phenomenon in the ocean, generates sudden strong shear currents that can significantly excite multi-mode and nonlinear vortex-induced vibrations (VIV) in risers. To reveal the transient nonlinear VIV responses of the deepwater drilling riser system under ISW, this study establishes a semi-empirical nonlinear fluid–structure interaction model. A nonlinear dynamic model of a riser system based on actual engineering configurations, considering both the geometric nonlinearity of the riser system and the nonlinearity of the soil. It couples the modified Van der Pol wake oscillator model. The ISW-induced velocity profile is used as the input to the dynamic model, and the structural dynamics are solved using the finite element method. The study reveals that ISW suppresses cross-flow (CF) vibration while amplifying in-line (IL) displacement, inducing significant bending moment responses near pycnocline. The riser vibration undergoes a mode-switching evolution from an ordered state to a disordered state and finally back to an ordered state in the temporal dimension. The energy distribution of the riser vibration exhibits spatial non-uniformity, reflecting a mode competition phenomenon. Moreover, during the strengthening phase of the ISW, the riser vibration shows continuous peaks, demonstrating an obvious multi-frequency phenomenon. The 2D phase portrait shows that the trajectory evolves from multiple non-overlapping irregular elliptical rings at the initial stage of the ISW to chaotic points near its maximum amplitude and finally reverts to irregular elliptical rings as the wave decays. The 3D phase portrait shows that the riser vibration trajectory appears as a tornado-like shape spiraling upward along the IL direction. Increasing the ISW amplitude or the current velocity significantly increases the extreme IL displacement in the deep layer. Increasing the top tension effectively increases the equivalent stiffness and natural frequency of the riser system, suppresses the nonlinear large-displacement response induced by ISW, and thereby prolongs the fatigue life of the structure.