计及液舱晃荡影响的半潜型浮式风机耦合分析与运动控制研究

Floating offshore wind turbine (FOWT) is the new trend in offshore wind energy exploitation. Subjected to environmental loadings from wind, waves and current, an FOWT is known to be affected by a number of coupling effects. Meanwhile, previous studies on floating structures carrying liquid cargoes show that liquid sloshing in cargo tanks has significant impacts on the motions of structures. However, the coupling of an FOWT and liquid sloshing in its ballast water tanks has been rarely considered in existing FOWT investigations. Due to the coupling effects, the motions of the floating foundation of an FOWT lead to the oscillations in the loadings and power of its wind turbine. As a result, it is feasible to improve the operation stability of an FOWT by studying how to control its motions. In this project, a combined numerical and experimental approach is adopted targeting semi-type FOWTs. A coupled analysis model is firstly developed based on a CFD method, taking into account liquid sloshing in ballast water tanks. Complex environmental conditions of wind, waves and current are considered, and multiple types of interactions present in an FOWT study are then analysed, including that between an FOWT and surrounding fluid flow, the interplay among the wind turbine, the floating foundation and its mooring lines, as well as the coupling of the FOWT and nonlinear liquid sloshing. Subsequently, a control strategy is established for the valves in the ballast water tanks, which aims to control the motions of an FOWT by adjusting the fluid flow in the tanks. The impacts of applying motion control on an FOWT are then analysed, with optimisation schemes put forward for the control strategy. Furthermore, the numerical models established in the project are validated against scaled model tests in a physical tank. Research findings from this project can provide theoretical guidance and technical support for the integrated performance evaluation and system design optimisation of FOWTs.

浮式风机的应用是海上风能开发的趋势。受风浪流等环境因素影响，浮式风机存在多重耦合作用。已有对载液浮式结构的研究表明液舱晃荡影响结构运动，但当前浮式风机分析忽略了其与压载水舱液体晃荡的耦合。由于耦合效应，浮式基础运动会引起风机载荷与功率波动，因此可通过研究控制其运动幅度来提升风机运转稳定性。本项目采用数值模拟与模型试验结合的手段，以半潜型浮式风机为研究对象，基于CFD方法建立考虑液舱晃荡影响的浮式风机耦合分析模型，开展浮式风机耦合特性研究，分析风浪流等复杂环境激励下浮式风机与流场、风机-浮式基础-系缆以及浮式风机与非线性液舱晃荡等耦合作用。在此基础上，建立压载水舱气阀控制策略，形成基于压载水流动的浮式风机运动控制研究方法，揭示运动控制对浮式风机的影响规律，提出控制策略优化方案。同时对建立的数值方法通过开展水池模型试验进行验证。研究成果可为浮式风机整体性能评估与系统设计优化提供理论指导与技术支持。

随着海上风能开发逐渐从浅海近岸向深远海挺进，浮式风机已经成为海洋可再生能源领域的研究热点。浮式风机由浮式平台支撑，受风浪流作用将产生明显的六自由度运动，这使得浮式风机耦合作用十分显著。本项目以半潜型浮式风机为研究对象，基于计算流体动力学方法建立了高精度浮式风机流固耦合分析模型，并在中国海洋大学山东省海洋工程重点实验室开展了物理模型试验对数值模型进行了验证，进而研究了风、浪、流等复杂环境荷载作用下浮式风机耦合动力性能，分析了不同环境工况下半潜型浮式风机的动力响应特性；在此基础上，参考船舶与海洋工程中减摇水舱设计，将浮式风机平台各立柱连通以使其中的压载水自由流动，通过构建浮式风机运动-压载水流动的耦合分析模型，探究了压载水流动对半潜型浮式风机动力响应特性的影响；同时，提出了基于压载水流动控制策略，形成了基于压载水流动的浮式风机运动控制分析方法，分析了压载水流动控制对半潜型浮式风机动力响应的影响，研究发现应用压载水流动控制策略可显著降低浮式风机纵摇响应幅度。项目执行期间，相关研究成果在船舶与海洋工程领域国内外高水平学术期刊及会议发表论文8篇，其中SCI论文4篇，EI论文3篇，参加国内外学术会议交流4次，授权发明专利2项，指导硕士研究生4人。项目研究成果可为浮式风机性能评估与设计优化提供技术支持，具有重要的科学研究意义与工程应用价值。