高层建筑群对街谷内颗粒物扩散特性的影响

Impact of high-rise buildings on particulate matter dispersion in urban street canyon

为了获得城市冠层内高层建筑群的高度变化对城市颗粒物污染的作用情况,采用大涡模拟方法研究了不同高层建筑群的街谷形状因子对街谷内空气流动与污染物扩散规律的影响。结果表明:在高层建筑群上方形成一个顺时针旋涡,旋涡中心位于城市峡谷内靠近高层建筑群背风处;随着街谷形状因子的增大,高层建筑群的滞留效应增强,导致高层建筑物上方的剪切层湍动能增强;当形状因子为2.5时,湍动能达到1.9 m^2·s^(-2),此时城市街谷内可吸入颗粒物的稀释扩散条件变差;在涡旋和气流夹带作用下,可吸入颗粒物浓度在垂直方向上分布具有明显的分层现象,大量可吸入颗粒物聚集于低建筑迎风面底部。不同街谷形状因子下街谷内空气流动与污染物扩散规律的探明将为有关部门制定相应规划提供参考。

In order to obtain the effects of height variation of high-rise buildings in urban canopy on theparticulate pollution, large-eddy simulation was used to study the influence of street shape factors of differenthigh-rise buildings on airflow and pollutant diffusion in the canyon. The simulation result shows that a clockwisevortex could be formed above the high-rise buildings, and its center is located near the lee of the high-risebuildings in the urban canyon. With the increase of the shape factor of the valley, the particulate-retention effectof the high-rise buildings will increase, which could strengthen the turbulent kinetic energy and air stagnation ofthe shear layer above the building. The dilution and diffusion conditions of the inhalable particles in the urbanstreet canyon become worse at the shape factor of 2.5 and the turbulent kinetic energy is 1.9 m2·s-2. With theentrainment of the vortex and the airflow, an obvious concentration stratification distribution will occur in thevertical direction for the inhalable particulates, a large number of them will gather at the bottom of windwardside of the low-rise buildings. To achieve the spread of particulate pollutants outside the urban street canyon, itis necessary to observe the law of airflow and pollutant diffusion with different aspect ratio, which will provide atheoretical basis for relevant government departments to formulate the corresponding policies and regulations.