树冠空间占用对不同高宽比街道行人热环境的影响

Effects of canopy space occupation on the thermal environment of pedestrians in the street with various aspect ratios

针对冠层大小的差异及在多大程度上影响不同深浅街谷内部行人小气候的问题,构建NE-WS和N-S走向的浅、中、深3种纵横比特征的街道,并利用ENVI-met模拟软件,分析不同大小的树冠对行人气温影响.结果表明:1)无论街谷深浅如何,植树总是引起上午行人气温的小幅升高;但是,植树可降低中午和下午的行人气温;2)树木对行人小气候的影响程度随着街谷深度的增加而减弱,因此行道树绿化差异所致的深街谷行人小气候差异将微乎其微;3)行道树对行人小气候的调节作用有限,建议在NE-WS和N-S走向的街道中种植带有小空隙率(0.125)的行道树,而不是让树冠相接形成连续树荫,以获得更好的降温和通风.

For the question of the extent differences in canopy size affect the pedestrian microclimate in street canyons with varying depths,this paper first builds streets models with three aspect ratios(AR)of shallow,medium,and deep canyons in both NE-WS and N-S directions.Using the ENVI-met software to analyze the impact of varying tree canopy sizes on pedestrian air temperature.The result shows that tree planting always raises pedestrian air temperature in the morning while droppin g it at noon and afternoon regardless of the depth of the street canyon.The influence of trees on the pedestrian microclimate reduces as the depth of the street canyon increases.Therefore,there is quite a little difference in pedestrian microclimate induced by street trees’different greening in deep street canyon.Street trees have a limited effect on regulating the pedestrian microclimate.To provide better cooling and ventilation,planting trees with tiny gaps(0.125)should be placed in the NE-WS and N-S streets instead of forming continuous shade.