耦合干涉效应的立管群涡激振动机理及变刚度过程控制模型研究

Marine riser is a significant part of offshore engineering. Vortex induced vibration is the main cause of fatigue failure of the riser under the combined excitations of marine environment loads. Compared with single riser, interference effect of riser group makes a significant difference in vortex induced vibration. And it also makes a great difference between design theory and analysis model of vortex induced vibration process of riser and the actual stress and motion state of riser, which becomes a serious threat for the security of riser. In this project, in order to reveal the vortex induced vibration mechanism of riser group coupling interference effect, the model experiments of variable parameters vortex-induced vibration of riser group will be carried out in a flume. The dynamic characteristics and dynamic response of the riser under the combined excitations of multiple fluids will be investigated and the response regularity of effective interference region for arrangement parameters will be explored. Based on the semi-empirical method and experimental data, variable stiffness coefficient is introduced by using ‘riser group structure - fluid among risers’ as carrier, a variable stiffness process control model of the riser coupling interference effect will be established by applying the structural dynamics, hydrodynamics theory and finite element method. Based on the control model, the numerical simulation for vortex induced vibration of the riser under the excitations of marine environment loads coupling interference effect will be conducted. And reasonable arrangement parameters among risers will be proposed, which will serve as scientific basis for the theoretical design and security service of riser group.

海洋立管是海洋工程结构的重要组成部分。海洋环境荷载作用下的涡激振动是导致立管产生疲劳损伤破坏的主要因素。相比单管涡激振动，立管群之间的干涉效应使立管的涡激振动规律产生显著变化，使传统的涡激振动过程设计理论及分析模型与立管实际受力及运动状态之间存在较大差异，对立管的安全服役构成严重威胁。本项目以立管群为研究对象，通过群管的变参数涡激振动水槽模型试验，研究多重流体的不同作用下立管的动力特性和动力响应，探索群管有效干涉区域对排列参数的响应规律，揭示耦合干涉效应的群管涡激振动机理。同时借鉴半经验法，结合模型试验，应用结构动力学、水动力学理论和有限单元法，以“群管结构—管间流体” 整体为载体，引入变刚度系数，建立耦合干涉效应的群管涡激振动变刚度过程控制模型，实现海洋环境荷载耦合干涉效应的立管涡激振动数值模拟，并由此提出合理排列参数，为立管群的理论设计及安全服役提供科学依据。

立管群之间的干涉效应使传统的涡激振动过程设计理论及分析模型与立管实际受力及运动状态之间存在较大差异，对立管的安全服役构成严重威胁。对于干涉效应的研究多数是基于单向性双管的基础布置，没有考虑“群管”模式下多重的流体作用及不同作用模式，“群管结构—管间流体”的耦合作用机制尚不清晰。本项目采用模型试验和数值模拟相结合的方法，探索了群管有效干涉区域对排列参数的响应规律，引入“干涉率”概念，量化了干涉效应对立管群涡激振动的影响，揭示了耦合干涉效应的群管涡激振动机理，得出了排列参数对干涉效应的影响权重，并确定了立管临界间距及尾流干涉的临界转换角度，分析了有效干涉区域内的主导因素及变化规律，建立了耦合干涉效应的群管涡激振动变刚度过程控制模型，实现了海洋环境荷载耦合干涉效应的立管涡激振动数值模拟，对降低立管在服役期间的干涉风险和完善立管涡激振动过程设计理论，具有重要的理论意义和工程应用价值。