Distributions of gust and peak factors at a pedestrian level in a simplified urban canopy obtained by particle image velocimetry
Distributions of gust and peak factors at a pedestrian level in a simplified urban canopy obtained by particle image velocimetry
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DOI：
10.1016/j.buildenv.2022.109350
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发表时间：
2022-07
影响因子：
7.4
通讯作者：
C. Hirose;T. Nomichi;N. Ikegaya
中科院分区：
文献类型：
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作者：
C. Hirose;T. Nomichi;N. Ikegaya
城市冠层内复杂的速度场影响了行人层面罕见的弱风速和强风速现象的发生。虽然粒子图像测速（PIV）被广泛用于确定速度分量，但由于周围建筑物的影响，它尚未应用于罕见风事件的行人空间。因此，在本研究中，通过在焦点块中插入激光光学系统，使用时间分辨PIV测量了简化的城市冠层内的两个速度分量。我们测定了冠层内行人水平的湍流统计、概率密度、阵风因子（GF）和峰值因子（PF）。在平均风速较低的位置，风速分量的概率密度函数趋于负偏态，而在平均风速较高的位置，风速分量的概率密度函数趋于接近高斯分布。在观测到较大速度的区域，GF值较小。然而，无论测量位置如何，PF的分布都小于GF。由于强风的重要性，PF可能是评价城市冠层内强风速度的一个更有用的指标。
The complex velocity fields within an urban canopy affect the occurrence of rare weak and strong wind-speed phenomena at the pedestrian level. Although particle image velocimetry (PIV) is widely used to determine velocity components, it has not been applied to pedestrian spaces for rare wind events, owing to the surrounding buildings. Therefore, in this study, two velocity components within a simplified urban canopy layer were measured using time-resolved PIV by inserting a laser optics system into a focal block. We determined the turbulent statistics, probability densities, gust factor (GF), and peak factor (PF) at the pedestrian level within the canopy layer. The probability density functions of the velocity components at positions with a lower mean wind speed tend to be negatively skewed, whereas those at positions with a higher mean wind speed tend to become closer to the Gaussian distribution. The GF values are small in the regions where a larger velocity is observed. However, the PF shows less distribution than the GF, regardless of the measurement position. Owing to the importance of strong gusts, the PF could be a more useful index for evaluating strong winds speed within the urban canopy layer.