| 典型深街谷内树木空间配置对行人呼吸高度处气流的影响 |
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| 引用本文： | 林定,申小云,朱勇兵,陈崇成.典型深街谷内树木空间配置对行人呼吸高度处气流的影响[J].地球信息科学,2018,20(9):1235-1243. |
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| 作者姓名： | 林定 申小云 朱勇兵 陈崇成 |
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| 作者单位： | 1. 空间数据挖掘与信息共享教育部重点实验室,福建省空间信息工程研究中心,福州大学,福州 3501162. 国民核生化灾害防护国家重点实验室,北京102205 |
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| 基金项目： | 国家自然科学基金项目（31200430）;福建省科技引导性项目（2016Y0058）;装备预演项目（40407020602） |
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| 摘 要： | 为揭示树木的不同空间配植方案对行人呼吸高度气流的影响,本文将树木视为均匀多孔介质,通过附加源项法从空气动力学角度用CFD模拟了H/W=2的典型深街谷几何内4种树木配植情景,实验表明,不同空间配置下树木对街谷内行人呼吸高度处局地气流的影响强弱在空间分布模式上差异悬殊：① 均匀种植的树木对街谷内行人呼吸高度的气流起到阻碍作用,不均匀种植则有效提升街谷的整体流速。4种空间配植方案下树木对气流的影响程度不同,阻碍作用从大到小的顺序为均匀间距8 m（Spa8m）>均匀间距6 m（Spa6m）>均匀间距20 m（Spa20m）>不均匀配植（Non-uniform）;对应的平均气流增强指标顺序为$\bar{D}_{spa8}$（-19.31%）<$\bar{D}_{spa6}$（-16.14%）<$\bar{D}_{spa20}$（-10.73%）<$\bar{D}_{non-uniform}$（1.25%）。② 对比不均匀和均匀的种植方案,不均匀植树的街谷内部行人呼吸高度的气流流速比其对照案例（均匀植树Spa8m方案）整体增强了106.49%。街谷中部不种树,在街谷两端配置树木并预留足够的自由空间的不均匀植树方案,能够让角涡渗入街谷中部,促使街谷内部的垂直漩涡和两端的水平角涡运动,增强湍流和垂直交换,有效减少了街道两端“风口效应”和街道中部“风影效应”的区域,改善了整个街谷行人呼吸平面的风环境。④ 合理空间配置的树木能够改善街谷内部的行人风环境。街谷内行人呼吸高度处的气流对局地条件很敏感,树木的局部配置（空间簇集、密度）将引起强烈的空间变化。在既有城市建筑布局条件下,如何通过谨慎的景观设计,利用树木等城市绿化措施有效地改善城市的行人风环境,缓解污染扩散、疾病传播等问题,本文的方法可提供一定的参考。
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| 关 键 词： | 树木 街谷 气流 数值模拟 行人风环境 |
| 收稿时间： | 2018-01-21 |
Effect of Spatial Distribution of Trees on the Airflow at Pedestrian Breath Height in the Typical Deep Street Canyon |
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| LIN Ding,SHEN Xiaoyun,ZHU Yongbing,CHEN Chongcheng.Effect of Spatial Distribution of Trees on the Airflow at Pedestrian Breath Height in the Typical Deep Street Canyon[J].Geo-information Science,2018,20(9):1235-1243. |
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| Authors: | LIN Ding SHEN Xiaoyun ZHU Yongbing CHEN Chongcheng |
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| Institution: | 1. Key Laboratory of Spatial Data Mining & Information Sharing of MOE, Spatial Information Research Center of Fujian, Fuzhou University, Fuzhou 350116, China;2. State Key Laboratory for Civilian Nuclear, Biological and Chemical Defence, Beijing 102205, China |
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| Abstract: | In order to show the degree of change of the airflow at pedestrian breath height due to trees, trees with four different spatial distribution inside the ideal deep street canyon (H/W = 2) were simulated by CFD from the aerodynamic point of view. Tree canopy was treated as uniform porous media, and an additional source term is integrated to account for additional dissipation due to trees. Our results show that the effect of different spatial configuration of trees on the airflow varies greatly with trees' spatial distribution pattern: (1) Within the street canyon, uniform planted trees hinder the pedestrian airflow while non-uniform planted trees increase its rate. The effects of the on pedestrian airflow are very different under the four spatial distributions. The order of the obstruction effect of trees on airflow from the largest to the smallest is evenly spaced 8m (Spa8m) > evenly spaced 6 m (Spa6m) > evenly spaced 20 m (Spa20m) > not uniformly planted (Non-uniform). The corresponding average airflow enhancement index sequence is$\bar{D}_{spa8}$（-19.31%）<$\bar{D}_{spa6}$（-16.14%）<$\bar{D}_{spa20}$（-10.73%）<$\bar{D}_{non-uniform}$（1.25%）. (2) The pedestrian airflow win the street canyon with uneven-planting was 106.49% higher than that in the control case (uniform tree Planting, Spa8m). Uneven-planting scheme is the case that trees are planted with the sufficient free space at both ends of the street and no trees in the middle. It can allow the corner vortex to infiltrate into the middle of the street valley, promote the vertical vortex inside the street valley and the horizontal vortex movement at both ends, enhance turbulence and vertical exchange, effectively reduce the “tuyere effect” at both ends of the street and the “calm wind effect” in the middle of the street. It improves the wind environment of the entire street valley at the pedestrian breathing plane. (3) Trees with reasonable spatial distribution can improve the street pedestrian wind environment. The airflow at the breath height of pedestrians in the street valley is very sensitive to the local conditions, and the configuration (spatial cluster and density) of the trees will cause a strong spatial change of it. These results point out the importance of trees' spatial distribution in urban greening measures under existing urban building layout with the goal of improving the pedestrian wind environment, alleviating the spread of pollution and the disease by careful landscape design. |
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| Keywords: | tree street canyon airflow numerical simulation pedestrian flow |
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