上游建筑对街道峡谷内流场和污染物分布特征的影响

利用数值模拟方法研究了不同的上游阻挡建筑布局下,行列式和错列式街谷内气流速度和污染物浓度场特征.结果指出,阻挡建筑的存在改变了街谷内的二次流,从而对流场和浓度场均有明显影响.在行列式街谷中,无论上游建筑以何种布局存在,都会减小街谷内污染物浓度.若不考虑上游建筑的存在,将会过高估计行列式街谷内污染程度;在错列式街谷中,与街谷建筑并列的上游阻挡建筑会减小街谷内污染物浓度,而与街谷建筑错列布置的阻挡建筑会增大街谷内污染物浓度;数值模拟结果还表明,街谷内污染物的扩散和清除效果受气流速度和涡流特性的共同作用.

Impacts of upstream buildings on the flow fields and pollutant distributions in street canyons

Numerical simulations were conducted to study the flow and concentration fields in both regular and staggered street canyons with different layouts of the upstream buildings. The results showed that the upstream buildings changed the wind speed and distorted the secondary flows in the canyons thus had significant effects on the flow and concentration fields. In the regular street canyons, the average pollutant concentrations could be reduced regardless of layout of the upstream buildings. The average concentration would be overestimated by numerical simulations without considering the existence of the upstream buildings in practice. In the staggered street canyons, when upstream buildings are aligned with street canyons, the pollutant concentrations in the street canyon could be reduced by the blocking effect. In contrast, when the upstream buildings are staggered with the canyons, the concentrations could be increased. The results also showed that the pollutant dispersion and removal in street canyons are effected by both the airflow velocity and local vortex characteristics.