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昆明市树木参数及种植形式对风环境的影响研究
A study on the effects of urban tree parameters and planting forms on the wind environment in Kunming
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摘要: 利用Phoenics 2019以数值模拟的方式研究树高(TH)、冠幅(CW)、枝下高(UBH)、叶面积指数(LAI)等树木参数对风环境的影响,探讨不同种植形式下的风环境特征。结果表明:树木对风环境的影响程度表现各异,1.5 m高度影响微弱,5 m高度影响最为明显,随着垂直距离的增加,风速变化趋于显著; LAI是风速发生改变的主要驱动因素,LAI与树木对风环境的影响程度呈正比,对风速的影响范围主要位于距离坐标原点水平距离8~18 m,随着水平距离的增加,风速先增加后逐渐趋于平稳;在垂直方向上,CW对风速的影响表现为从中心位置向两侧逐渐增加,TH对风速的影响与树木冠层分布范围基本一致,随着UBH的增加,高干扰风速区间位置逐渐升高;不同种植形式下的最大风速和最小风速分别出现在角流区和风影区,并且表现出不同的风影区长度、低风速区面积和风速离散度;迎风区、角流区、涡流区和风影区空气龄的变化趋势为“先增后降”,不同种植形式下空气龄的变异系数有较大区别。研究结果可为城市树木的选择和管理提供参考,对于缓解污染扩散、疾病传播和热岛效应等城市问题具有重要的参考价值,对于改善城市风环境并提高室外空间舒适度有着重要意义。Abstract: The impact of tree variables such as tree height(TH), crown width(CW), under branch height(UBH), and leaf area index(LAI) on the wind environment was scrutinized through numerical modeling utilizing Phoenics 2019 to elucidate the attributes of the wind environment under different planting configurations. The findings demonstrated that: The magnitude of influence of trees on the wind environment fluctuated. The influence of trees on the wind environment ranges from subtle at 1.5 m to most pronounced at 5 m, and the alteration in wind speed tends to be substantial with the augmentation of vertical distance. LAI is the primary driving factor for the modification of wind speed, which is positively correlated to the degree of influence of trees on the wind environment, and the influence domain of wind speed is situated within the range of 8-18 m from the origin of the coordinates, and the wind speed initially escalates and subsequently tends to stabilize with the expansion of horizontal distance. The influence of trees on the wind environment in the vicinity of 1.5 m height is minimal at 1.5 m height, and most evident at 5 m height. tends to be stable; In the vertical direction, the influence of CW on wind speed exhibits a gradual escalation from the center to both sides, and the influence of TH on wind speed aligns with the distribution range of the tree canopy; with the augmentation of UBH, the location of the high interference wind speed interval progressively ascends; The maximum and minimum wind speeds under different planting configurations manifest in the angular flow zone and wind shadow zone, respectively, and exhibit diverse lengths of the wind shadow zone, area of the low-wind speed zone and dispersion of the wind speeds. The trajectory of air age in windward, angular flow, eddy flow, and wind shadow zones was "Increase first and then decrease", and the coefficients of variation of air age under different planting configurations were considerably disparate. The outcomes of this study can furnish a scientific rationale for the selection and management of urban trees, which is a crucial reference value for the mitigation of urban issues such as pollution diffusion, disease transmission, and heat island effect, and is of paramount significance for the amelioration of the urban wind environment and the comfort of outdoor space.