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摘要
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 . The difference of Reynolds stress at height between the control and sensitivity experiments is found to increase with the increase in the plan-area index () for . Thus, values of 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 . The exuberance in the control experiment at height is found to decrease with increase in the building-height variability. Although the extreme momentum flux at height in the control experiment appears around buildings, it contributes little to the total Reynolds stress and is not associated with coherent motions.
- 出版日期2018-7
- 单位防灾科技学院
