基于参数化耦合边界的深海浮式系统整体耦合模型及时域响应特征研究

The large floater and its flexible mooring/riser system interact with each other in a complex physical mechanism. At present, the simplified coupling model and indirect time-domain analysis method based on the small amplitude perturbation theory cannot take full account of the real coupling effect between the floater with large drift motion and its mooring/riser system. This project will be executed by means of theoretical analysis, numerical simulation and experimental verification. First, the influence of various boundary parameters on the dynamic response of the floating system will be investigated, hereby the key design parameters that can reflect the real coupling mechanism between the floater and mooring lines/risers will be determined and selected as the boundary condition in the fully coupled analysis model. At this stage, the whole coupling model of floating body and mooring/riser can be established. Second, considering nonlinear changes of floater’s wave encounter frequency, body boundary condition and the damping characteristics induced by the large amplitude motion of the floater, the time-domain analysis method will be modified and developed based on the time-domain Green function. Third, effects of system damping and added mass on the system response spectra and distribution characteristics will be discussed, and then a new probability distribution model, which can reflect broadband and non-Gaussian characteristics of dynamic response, will be established by utilizing hypothesis testing technology. The aim of this project is to expand and develop the theory of analysis and prediction of the dynamic response of the floating structure system in deep water.

大型浮体与柔性系泊/立管形成一个相互作用、相互影响的整体系统，耦合机理复杂。目前通常采用的简化边界分析模型和基于摄动展开理论的间接时域计算方法不能充分考虑大幅漂移浮体与系泊/立管的真实耦合效应。本项目拟采用理论分析、数值模拟和模型试验相结合的研究手段，探讨不同边界参数对系统动力响应的影响规律，辨识、选取关键设计参量建立可真实反映子系统间耦合作用机制的参数化边界，发展浮体-系泊/立管整体耦合动力学模型；考虑平台大幅运动引起的波浪遭遇频率、物面边界及系统阻尼的非线性变化，基于时域格林函数发展和完善浮式结构系统耦合动力响应的全时域分析方法；分析阻尼、附加质量等参数对系统响应时频特性和分布特征的影响作用，通过假设检验技术手段建立可反映系统响应宽带双峰谱特征和非高斯特性的概率分布模型。本项目的研究可丰富并发展深海浮式结构系统耦合动力响应的分析和预报理论，为我国南海深水资源开发提供理论指导和技术支撑。

深海浮式结构系统复杂，耦合效应明显，动力响应规律不清，为工程设计带来巨大挑战。本项目建立了大型浮体-系泊系统、系泊缆-海床基础的耦合边界模型，探讨了不同耦合边界模型对系统整体响应、局部强度等动力响应的影响规律，并进一步建立了理论基础更加完备的整体耦合模型；考虑浮体大位移、系泊缆大变形、退化海床基础等非线性因素，发展完善了浮体/系泊系统耦合动力响应的时域分析方法；然而，时域分析方法计算效率低，不利于工程设计应用，本项目创新提出了整体系统耦合动力响应的二阶频域分析方法与时/频混合域分析方法，显著提高了复杂深海结构系统耦合动力响应的分析效率与精度；进一步，对深海浮式结构系统动力响应的时频特性和分布特征开展详细研究，探讨了不同浮式平台结构型式、不同水深、不同系泊形态等对浮体运动、系缆张力等动力响应非高斯特性的影响规律，引入新的分布模型，对系统动力响应进行描述，得到了较好的效果。同时，本项目开展了波候变化与海洋腐蚀对整体系统动力响应的影响研究，探讨了多失效模式联合的系泊系统可靠性评估模型与评估方法。研究成果可为我国南海深水资源开发提供理论指导、技术支撑与设计工具。