风力机对大气边界层近地层影响的数值模拟

为研究风力机运行对大气边界层近地层的潜在影响，采用 Gambit 软件建立风力机及风场模型，应用 UDF加载边界层速度分布函数作为流场入口边界条件，基于尾流特性及湍流理论，应用 Fluent 软件模拟单台风力机运行对大气边界层近地层的影响，通过分析风力机下游不同位置处的速度及湍动能以及其随高度的变化情况来进行分析研究。模拟结果表明风力机的运行会造成近地层内原本均匀分布的大气流场发生明显变化。与初始速度分布相比，流体流经风力机后，轮毂处风速迅速降低，随后逐渐增加，但随着向下游的延伸，速度增加的梯度逐渐降低，且在距离风力机17倍风轮直径后仍未增至来流速度；在竖直方向上速度分布呈现出逐渐增加的趋势，但在风轮位置处明显下降，随着空气继续向后流动，影响面积在扩大，但是趋势逐渐变缓。同时湍动能也发生较大变化，在近风轮处，由于轮毂区域的风速与周边的风速存在较大差异，所以造成近风轮处的湍动能迅速增大，随着流体向下游的延伸，与周边流体逐渐混合扩散，湍动能逐渐降低；湍动能在竖直高度上的分布在近尾迹区呈现出由地面至高空先减小后增大，再减小再增大的趋势；而远尾迹区域则先减后增，不过在到达一定高度后几乎都不再变化。由于大气各种通量的变化等也与风速、湍动能相关，所以风力机会对对其周边环境造成影响而不仅仅局限于近地层的风速、湍动能。

Numerical simulation for influences of a wind turbine on surface-level of atmospheric boundary layer

For the study of potential influences of a wind turbine on the surface layer of atmospheric boundary layer,Gambit software was chosen to model the wind turbine and simulate the whole flow field.The velocity distribution function of the boundary layer was loaded by the UDF as the inlet boundary condition.Based on a wake model and combined with the turbulence theory,Fluent software was used to simulate the variable surface layer of the atmospheric boundary layer caused by the single wind turbine.By analyzing the characteristics of the velocity and the turbulent kinetic energy in the wind turbine downstream,the effect was investigated on the atmospheric boundary layer.The simulation results show that the uniform distribution of the flow in the atmospheric boundary layer is changed intensively by the operation of the wind turbine.Compared with the original velocity distribution,the wind speed reduces rapidly after pass the wind turbine and then increases gradually,but the increase rate decreases gradually,and the velocity at the distance of 17 times of the turbine diameter still can’t meet the initial speed. The velocity distribution in vertical direction presents a gradually increasing trend, but is significantly low in the rotor position.The influenced area downward expands,but the expansion is gradually slow.The turbulent kinetic energy also changes greatly at hub area,because of the wind speed of the hub area different from that in the surrounding.The airflow mixes with the surrounding fluid downstream,leading to that the turbulent kinetic energy gradually reduces. The turbulent kinetic energy no longer changes at a certain height.Due to the variety of various fluxes related to wind speed and turbulence kinetic energy,the influence of the wind turbine on the surrounding environment may not limit to the variety of the wind speed and the turbulence kinetic energy in the surface layer.