筒型基础气浮拖航水动力耦合运动机理及性态控制研究

A bucket foundation is a novel and environmentally friendly foundation for offshore wind turbines. Its characteristics include onshore batched prefabrication, offshore air-floating transportation, rapid construction, low cost, high reliability and good durability. As a new type of air floating structure, the bucket foundation is different from the conventional transportation of foundation because it has a more complicated towing mechanism. Especially, both the coupled “gas-liquid-solid” mechanism and the dynamic characteristics of floating towing are worth being further investigated. This project conducts a systematical study on the dynamic characteristics of bucket foundation. In terms of the theoretical and experimental study, a stiffness analytic model is developed considering the air-water coupled effects within the subdivision boundary of the bucket foundation. With an optimal subdivision scheme, the mechanism of the stochastic dynamic nonlinear stability is analyzed for the bucket foundation in irregular waves. Furthermore, model parameters are accurately determined for describing the non-stationary nonlinear behavior of the bucket foundation. Finally, this project establishes the prediction model on the response of the bucket foundation supported by air cushions during its towing process, which will provide some theoretical guidance for the safety and efficiency of the towing for the bucket foundation in complex sea conditions.

筒型基础是一种应用前景广阔的环境友好型基础型式，具有可陆上批量预制、海上气浮运输和快速安装、成本低廉、安全性高和耐久性好等优势。不同于传统的基础结构运输，筒型基础作为一种可气浮运输结构，其拖航运动机理较为复杂，尤其是浮运过程中“气-液-固”耦合作用机理及浮运动力特性还有待深入研究。本项目研究针对筒型基础的气浮拖航动力特性问题，通过理论分析和模型试验建立考虑基础舱室边界的气垫/水塞耦合刚度动力计算模型，明晰考虑优化分舱条件下海上风电筒型基础在不规则波浪作用下随机动态非线性稳性机理，准确选取描述气浮基础非线性时变运动状态的模型参数，形成筒型基础气浮拖航安全性态响应和预测模型，为筒型基础长距离复杂海况下安全、高效的气浮拖航提供理论指导。

筒型基础是一种新兴的环境友好型海上风电基础结构，具有建造简单、施工高效、综合成本低等特点，逐渐受到了国内外海上风电工程界的关注和认可。与常见的实浮结构相比，气浮筒型基础在拖航过程中，除了考虑水体与基础的相互作用外（流固耦合），还需要考虑气垫-水塞界面运动特性（气液耦合）及气水弹簧对结构动力响应特性的相互影响（气液固耦合）。本项目主要以工程原型筒型基础为研究对象，通过理论和数值分析、模型试验和现场监测等方法，系统研究了筒型基础气浮拖航过程中“气-液-固”耦合机理及浮运特性，具体包括：（1）针对筒型基础，推导了气浮筒型基础正浮态静稳性公式，结合运动方程求解了附加质量等水动力学参数，明晰了筒型基础“气-液-固”耦合气垫特性、气液界面转换、气水耦合刚度变化及基础气浮稳性演化等规律。（2）对比分析了单筒带分舱气浮筒型基础与单筒无分舱气浮筒型基础的拖航阻力、摇摆及垂荡运动幅值和气垫压力的差异性及相关参数的敏感性，分析了气浮拖航过程周围流场分布规律，明晰了恒定气垫作用下的筒型基础与周围流场的流固作用机制。（3）采用波浪拖航试验法对比分析了单筒带分舱筒型基础及实浮体基础在复杂波浪条件下拖航运动响应差异机理，通过考虑不同吃水、拖航速度、拖航方向、波高、波浪周期对拖缆力、筒内气压力、筒底水压力和基础六自由度的影响，分析了“气-液-固”相互作用对气浮筒型基础耐波性的影响机理。（4）针对实际拖航施工中可能出现的破舱情况，分析了筒型基础由破舱失稳到充气调平新稳态的整个“气垫-水垫-结构”耦合姿态变化过程，验证了筒型基础由破舱失稳到充气调平新稳态再到调平后进行波浪拖航的可操作性。（5）通过海上风电一步式运输安装船1:50拖航模型实验室试验、海上风电一步式运输安装船1:10拖航模型海上试验，海上风电一步式运输海上运输实例测试，研究了基于气浮筒型基础的一体化运输系统运动响应机理和分析预测模型，并指导了相关工程。