极限作业海况下浅吃水Spar型浮式风力机非线性动力响应及运动稳定性研究

浮式风力机在极限作业海况下基础发生大幅运动，影响风力机作业安全与稳定性。本项目基于现代非线性动力学理论，开展极限作业海况下浅吃水Spar型浮式风力机非线性动力响应及运动稳定性研究。针对底部带有环形减动结构的浅吃水Spar型浮式风力机，结合极限作业海况，考虑叶片气动载荷、基础水动力载荷、塔柱叶片振动变形、系泊载荷等因素，建立浮式风力机系统气动-水动-结构耦合非线性动力学模型。基于摄动理论推导多频载荷作用下基础非线性运动近似解析解，研究基础运动的非线性谐振响应。基于分岔理论确定基础在极限作业海况下的运动失稳参数域。评估非线性气动阻尼及非线性回复刚度对浅吃水Spar型浮式基础非线性运动及稳定性的影响，揭示浅吃水Spar型浮式风力机在极限作业海况下引发运动失效的动力条件和环境条件。本研究旨在提升浮式风力机在恶劣海洋环境条件下作业的安全性，为我国海上浮式风力机的设计、优化及动力性能评估奠定理论基础。

The large motion of foundation occurs when the floating offshore wind turbine (FOWT) operates under the extreme operational sea state. It will affect the safety and stability of the operation of wind turbine. Based on the modern nonlinear dynamics theory, the nonlinear dynamic response and motion stability of the reduced draft Spar-type FOWT are studied under the extreme operational sea state. This proposal aims at the reduced draft Spar-type FOWT with an annular bottom anti-motion structure. In terms of the extreme operational sea state, the aero-hydro-structural coupling nonlinear dynamic model of FOWT system is established, taking the factors, including aerodynamic loads on blade, hydrodynamic loads on foundation, vibration deformations of tower and blades, mooring loads into consideration. By adopting the perturbation theory algorithm, the approximate analytical solutions of the nonlinear motion of the foundation are derived under the multiple-frequency loads. The resonance oscillations are investigated. Based on the bifurcation theory, the parametric field of motion instability is determined. The influence of nonlinear aerodynamic damping and nonlinear restoring stiffness on both nonlinear motion and stability of the reduced draft Spar-type FOWT foundation is evaluated. The motion-failure dynamic and environmental conditions of the FOWT under the extreme operational sea state are revealed. According to this research, the FOWT operation safety under the bad offshore environmental conditions is increased. This research will lay the theoretical foundation for the design, optimization and dynamics feature evaluation of FOWT.