The proper orthogonal decomposition has been applied on a full-scale horizontal-axis wind turbine to shed light on the wake characteristics behind the wind turbine. In reality, the blade tip experiences high deflections even at the rated conditions which definitely alter the wake flow field, and in the case of a wind farm, may complicate the inlet conditions of the downstream wind turbine. The turbine under consideration is the full-scale model of the National Renewable Energy Laboratory 5MW onshore wind turbine which is accompanied by several simulation complexities including turbulence, mesh motion and fluid-structure interaction. Results indicated an almost similar modal behaviour for the rigid and flexible turbines at the wake region. In addition, more flow structures in terms of local vortices and fluctuating velocity fields take place at the far wake region. The flow structures due to the wake shed from the tower tend to move towards the center and merge with that of the nacelle leading to an integral vortical structure 2.5 diameter away from the rotor. Also, it is concluded that the exclusion of the tower leads to missing a major part of the wake structures, especially at far-wake positions.

翻译：采用本征正交分解方法对全尺寸水平轴风力机进行了分析，以揭示风力机后方的尾迹特性。实际运行中，即使在额定工况下，叶尖也会发生显著变形，这必然改变尾迹流场，并在风电场场景中可能影响下游风力机的入流条件。本研究考虑的风力机为美国国家可再生能源实验室5兆瓦陆上风力机的全尺寸模型，其模拟涉及湍流、网格运动及流固耦合等复杂技术。结果表明，在尾迹区域，刚性与柔性风力机的模态行为几乎一致。此外，在远尾迹区域出现了更多局部涡旋和脉动速度场等流动结构。由塔架脱落产生的流动结构趋向于向中心移动，并与机舱脱落结构合并，在距离转子2.5倍直径处形成整体涡旋结构。同时发现，忽略塔架会导致尾迹结构的主要部分缺失，尤其在远尾迹位置。