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Title: Large-Eddy-Simulation Study of the Effects of Building-Height Variability on Turbulent Flows over an Actual Urban Area
Authors: Yoshida, Toshiya
Takemi, Tetsuya  kyouindb  KAKEN_id  orcid (unconfirmed)
Horiguchi, Mitsuaki  kyouindb  KAKEN_id
Author's alias: 吉田, 敏哉
竹見, 哲也
堀口, 光章
Keywords: Actual urban building
Large-eddy simulation
Atmospheric turbulence
Roughness parameter
Reynolds stress
Quadrant analysis
Issue Date: Jul-2018
Publisher: Springer Netherlands
Journal title: Boundary-Layer Meteorology
Volume: 168
Issue: 1
Start page: 127
End page: 153
Abstract: Large-eddy simulation (LES) is used to investigate the effects of building-height variability on turbulent flows over an actual urban area, the city of Kyoto, which is reproduced using a 2-m resolution digital surface dataset. Comparison of the morphological characteristics of Kyoto with those of European, North American, and other Japanese cities indicates a similarity to European cities but with more variable building heights. The performance of the LES model is validated and found to be consistent with turbulence observations obtained from a meteorological tower and from Doppler lidar. We conducted the following two numerical experiments: a control experiment using Kyoto buildings, and a sensitivity experiment in which all the building heights are set to the average height over the computational region hall . The difference of Reynolds stress at height z=2.5h[all] between the control and sensitivity experiments is found to increase with the increase in the plan-area index ( λp ) for λp>0.32 . Thus, values of λp≈0.3 can be regarded as a threshold for distinguishing the effects of building-height variability. The quadrant analysis reveals that sweeps contribute to the increase in the Reynolds stress in the control experiment at a height z=2.5h[all] . The exuberance in the control experiment at height z=0.5h[all] is found to decrease with increase in the building-height variability. Although the extreme momentum flux at height z=2.5h[all] in the control experiment appears around buildings, it contributes little to the total Reynolds stress and is not associated with coherent motions.
Rights: The final publication is available at Springer via
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DOI(Published Version): 10.1007/s10546-018-0344-8
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