剪切来流条件下风力机尾流场特性实验研究

An Experimental Investigation on the Characteristics of Wind Turbine Wake Under Incoming Shear Flow

以水平轴风力机模型为研究对象,利用一维热线测速技术,在Eiffel型风洞中研究了湍流边界层条件下风力机尾流场特性。实验结果表明,和平均速度、湍流强度等特性一样,湍流积分时间在尾流场中也出现衰减,并随风力机下游距离增加逐步恢复,在x/dT=10处,约恢复至来流的70%;受边界层影响,3种流场特性在竖直平面均呈非对称分布。基于频谱分析,在尾流场不同位置,不同尺度湍流结构对流场湍动能量的贡献度分布情况不一样。在风轮区域内,尾流场中湍动能量在近流场主要受风力机旋转影响,在远流场,尺度大于风力机直径的低频微团则起到主导作用,同时,基于无量纲的斯特劳哈尔数表明,在远流场(x/dT>4)存在不稳定的尾流弯曲现象。

Taking the horizontal axis wind turbine model as the research object,the characteristics of wind turbine wake under turbulent boundary layer were studied in Eiffel-type wind tunnel by using one-dimensional hot-wire anemometry. Results suggest that the integral time scale also attenuates in the wake and recovers gradually with the increase of the downstream distance of the wind turbine,which is similar to the characteristics of mean velocity and turbulence intensity, and up to roughly 70% of that of the incoming flow upon reaching x/dT=10.Due to the effect of turbulent boundary layer,the distribution of these three kinds of flow characteristics are asymmetric in vertical plane.According to the spectra analysis,the contribution to the turbulent fluctuations energy by multi-scale structures is different at various locations inside the wake.Within the turbine region,it is noted that turbulent kinematic energy is mainly contributed by wind turbine rotation kinematic in the near wake,while in the far wake is modulated by low-frequency flow structure whose scale is larger than the diameter of wind turbine. Meanwhile,based on the non-dimensional Strouhal number,it is shown that the unstable wake meandering phenomenon exists in the far wake region (x/dT >4).