深海立管在海流等海洋环境载荷作用下易发生涡激振动现象。当前针对立管涡激振动研究大多以恒定轴向张力状态和定常流环境为预置条件。本项目针对超细长立管在顶端浮体多自由度运动所引发的轴向张力变化等动态边界条件以及非均匀、非定常组合流场激励下的涡激振动问题开展研究。采用理论分析、数值模拟、试验对比相结合的手段，开展基于五参数耦合受迫振荡流体力载荷模型的时域数值预报方法研究；探索时变张力激励下立管参激-涡激耦合共振机制及响应特性，揭示多频多幅动态张力诱发涡激强共振的力学机理与参数化临界条件；研究非均匀、非定常流场下立管涡激振动激发机制及流体力时空分布特性，表征不同形式的振荡流与定常背景洋流叠加效应对立管涡激载荷的作用与影响；结合实海域典型短期海况条件，开展浮体运动诱发立管非线性响应研究，揭示多参数耦合作用机理，探究涡激振动疲劳载荷长期分布模型和规律，为深海立管的优化设计和安全评估提供理论与技术支撑。

The phenomenon of the nonlinear vortex-induced vibration (VIV) occurs under current loads for riser systems. The previous studies on this problem are mostly based on the constant axial tension and steady flow condition. In this project, VIV response under time-varying boundary conditions (i.e. axial tension variation induced by periodic motions of the top-end floating vessels) and complex environment (unsteady flow field) are to be investigated. Theoretical analysis, numerical simulations and model tests are to be carried out to investigate the time-domain numerical prediction approach based on a five-parameter coupled forced vibration hydrodynamic model. The resonance mechanism of the parametric excitation and vortex excitation as well as the response characteristics under time-varying tensions are to be discussed. The critical parameters of the strong resonance induced by VIV with single- or multi-frequency time-varying tension excitations are to be revealed. The VIV response characteristics of the risers under non-uniform and unsteady flow fields are investigated, and the combined effects of different oscillatory flows and steady background current on VIV hydrodynamic forces are to be presented. The influence laws of the multi-parametric excitations on the nonlinear response and long-term fatigue loads distribution of the risers will be investigated. This research work may provide important theoretical foundations for structural optimal design and safety assessment.