指数律参数选取对指数和廓线精度的影响

Influence of Exponential Parameters Selection on Exponent and Profiles Precision

基于广州市主城区水平比例尺为1∶7 000和垂直比例尺分别为1∶500、1∶1 000、1∶2 000的三维建筑模型,在B类边界层中性流条件下进行风洞模拟.利用26个测点、15个高度的西北和东南盛行风况下的风速数据,分析指数律参考高度zref、零平面位移d和采样厚度t等3个参数对指数α和拟合精度的不确定性影响,并为指数律应用中精度的提高提供了相应的建议.实验结果表明:参考测点最高高度α的均值和离散度相对较小,且拟合较为理想;d的引入能提高拟合精度,且与α呈负相关;不考虑零平面位移d的指数律对下垫面非均质、测点众多的研究更为实际;不同粗糙程度的下垫面,α在0.25~1 H廓线厚度段内收敛,0.25~1 H是理想的采样厚度.

Based on the 3 D model of Guangzhou main built-up area at 1 ∶ 7 000 horizontal scale,1 ∶ 500,1 ∶ 1 000,1 ∶ 2 000 vertical scale respectively,a wind tunnel simulation is carried out on the neutral flow of B atmospheric boundary layer. With wind velocities in more than 26 test points,15 heights of each prevailed wind of the northwest and southeast,the uncertainties generated by reference height zref,zero-plane displacement height d and sample thickness t to exponent α and fitting precision are all discussed,which provide some guidance to raise fitting precision on power law applications later. It is found that a reference height equal to maximum height of test points has a relatively smaller mean value and dispersion of α,and a better fitting precision than other zref;d can improve fitting precision and is correlated with α negatively. The exponential law of d in the zero plane displacement is not considered; it is more practical especially for the researches of inhomogeneous terrain and numerous test points. In differently rough terrain,α converges at 0.25 ~ 1 H of the thickness of wind profiles and 0.25 ~ 1 H is the ideal sampling thickness.