非孤立街道峡谷大气流动及污染物扩散特征

实际城市街道皆为非孤立街道,采用数值模拟方法研究了等高与不等高非孤立街道峡谷的大气流动及汽车排放污染物扩散特征.通过与已有的风洞实验结果对比,发现二者较吻合,并且目标街道峡谷上下游建筑物的存在对目标峡谷内部的流场和浓度场有很大的影响.与孤立街道峡谷相比,非孤立街道峡谷中污染物的浓度要远高于孤立街道峡谷中污染物的浓度,而且随着上下游建筑物的增加,使到达目标街道峡谷的风速相对减弱,污染物在峡谷中难以扩散,造成了峡谷内部污染物浓度会随着峡谷数的增加而增大.并且发现不等高峡谷建筑物高度存在一个临界点. 

Characteristics of Airflow and Vehicular Exhaust Pollutant Dispersion in Non-Isolated Urban Street Canyons

The actual urban streets are all non-isolated urban streets. The numerical simulation was used to study the airflow and vehicle emission pollutant dispersion in non-isolated urban street canyons. The numerical results have a good agreement with the experimental data and it is found that the existence of the upstream and downstream buildings of the target street canyon has significant influence on the wind field and concentration distribution by comparing with the results of the previous wind tunnel experiment. The concentration of the vehicle exhausted pollutant is much higher than the concentration in the isolated street canyon. With the increase of the number of upstream and downstream buildings, the wind velocity in the target street canyon is relatively weaker, which results in a higher pollutant concentration in the canyon, It was also found that there exists a critical height when the heights of buildings at both sides are not equal.