Median values of daytime (11:00–17:00 LST) and nighttime (00:00–06:00 LST) turbulence intensity (TI) (%), shear exponent (α) (unitless), and vertical potential temperature gradient (Δθ/Δz) (°C m−1) for each wind sector (see figure 1)

Table 1. Median values of daytime (11:00–17:00 LST) and nighttime (00:00–06:00 LST) turbulence intensity (TI) (%), shear exponent (α) (unitless), and vertical potential temperature gradient (Δθ/Δz) (°C m−1) for each wind sector (see figure 1). Abstract Observations of wakes from individual wind turbines and a multi-megawatt wind energy installation in the Midwestern US indicate that directly downstream of a turbine (at a distance of 190 m, or 2.4 rotor diameters (D)), there is a clear impact on wind speed and turbulence intensity (TI) throughout the rotor swept area. However, at a downwind distance of 2.1 km (26 D downstream of the closest wind turbine) the wake of the whole wind farm is not evident. There is no significant reduction of hub-height wind speed or increase in TI especially during daytime. Thus, in high turbulence regimes even very large wind installations may have only a modest impact on downstream flow fields. No impact is observable in daytime vertical potential temperature gradients at downwind distances of >2 km, but at night the presence of the wind farm does significantly decrease the vertical gradients of potential temperature (though the profile remains stably stratified), largely by increasing the temperature at 2 m.

表1 各风区（见图1）的日间（11:00–17:00 地方太阳时，Local Solar Time, LST）与夜间（00:00–06:00 地方太阳时，LST）湍流强度（Turbulence Intensity, TI，%）、剪切指数（Shear Exponent, α，无量纲）及垂直位温梯度（Vertical Potential Temperature Gradient, Δθ/Δz，°C·m⁻¹）的中位数。摘要：针对美国中西部地区单台风力涡轮机与多兆瓦级风电场站尾流的观测研究表明，在涡轮机正下游（距离190米，即2.4倍转子直径（Rotor Diameter, D）），整个转子扫风区域的风速与湍流强度（TI）均受到显著影响。然而，当处于下风向2.1公里处（即最近一台涡轮机下游26倍转子直径D）时，整个风电场的尾流已无明显特征。尤其在日间，轮毂高度处的风速未出现显著降低，湍流强度也未出现明显升高。因此，在高湍流工况下，即便超大型风电场站对下游流场的影响也较为有限。当日时下风向距离超过2公里时，未观测到垂直位温梯度出现明显变化；但夜间，风电场的存在会显著降低位温垂直梯度（尽管此时大气层结仍保持稳定层结），这一效应主要通过提升2米高度处的气温实现。