多向波浪作用下海上风机基础水动力特性的数值研究

With the development of offshore wind power engineering, the diameter of wind turbine foundation and pile cap size increase as water depth and unit capacity increase. They are gradually close to the division area of large and small scale structure. In the calculation of wave loads on medium scale structures, the viscous effect and diffraction effect are equally important. Moreover, the real sea waves are multi-directional random waves, wave directionality has an important effect on the wave load on offshore structures. This project aims to establish a coupling model based on the potential and OpenFOAM numerical wave tank to study the interaction of real sea waves with wind turbine foundation. In the inner domain of the coupling model, the transient flow field and the real sea wave loads on the structure will be calculated efficiently. For the outer domain, the complex wave field will be simulated exactly. The coupling model has the advantage of efficient and precise. Further, in order to investigate the effects of viscosity, nonlinearity and directional distribution of real sea waves to the wave load on wind turbine foundation, the interaction of multi-directional irregular waves with different relative scale wind turbine foundation will be systematically calculated. Besides, the present project focuses on the hydrodynamic characteristic of medium scale structure and studies the influence of the diffraction force and viscous force on it. The conclusions can provide scientific reference for the design of offshore wind turbine foundation.

随着海上风电工程的发展，风机基础的桩径及承台尺寸随水深和单机容量的增大而增大，逐渐接近划分大、小尺度结构的临界区域，在计算中等尺度结构所受波浪荷载时，需同时考虑粘性和绕射效应的影响。另外，真实的波浪是多向不规则波浪，波浪的方向分布对结构物受力大小和方向具有重要影响。为了研究真实波浪与风机基础的作用，本项目首先拟根据势流水池适于较大区域波浪传播计算和OpenFOAM模型适于精细模拟波浪与结构物作用的特点，建立两者间的耦合模型，兼顾计算精度和效率，实现内域近场结构物的瞬变流场形态、结构物所受真实波浪荷载的高效计算、外域远场复杂波浪的精细模拟。进一步，系统地对多向不规则波与不同相对尺度风机基础的相互作用进行模拟，以明确流体粘性、波浪的非线性和方向分布等对风机基础所受波浪荷载的影响规律。着重考虑中等尺度结构物的水动力特性，研究粘性力和绕射力对其影响。所得成果可为海上风机基础的合理设计提供科学依据。

随着海上风电工程的发展，风机基础的桩径及承台尺寸随水深和单机容量的增大而增大，逐渐接近划分大、小尺度结构的临界区域，在计算中等尺度结构所受波浪荷载时，需同时考虑粘性和绕射效应的影响。另外，真实的波浪是多向不规则波浪，波浪的方向分布对结构物受力大小和方向具有重要影响。项目基于势流理论和求解Navier-Stokes方程的方法建立了可以高效、高精度模拟多向不规则波浪传播及其与结构物作用的数值耦合模型，实现内域近场结构物的瞬变流场形态、结构物所受真实波浪荷载的高效计算、外域远场复杂波浪的精细模拟。进一步对多向不规则波浪与不同海上风电基础的相互作用进行了模拟，得到了相对尺度和波浪方向分布对风机基础所受波浪力和爬高的影响规律，结果表明相对尺度和方向分布对波浪荷载影响显著。相关研究成果可用于风机基础的设计中，所建立的耦合模型在海洋工程领域波浪与结构物相互作用的数值模拟中具有较好的应用前景。