中文摘要：

城市中的大部分街谷都存在上游阻挡建筑。为考察阻挡建筑对街谷内空气环境的影响，通过数值计算方法研究分析了上游阻挡建筑对街谷内空气品质的影响作用，结果表明，在常规建筑间距范围内，街谷湍流强度、平均风速和风速波动范围均随着上游阻挡建筑间距增大而减小，这将导致当上游阻挡建筑与街谷建筑间距从15m 增加到60m 时，街谷空间污染物平均浓度增大36%，近地空间增大41%。因此，实际设计中街谷上游阻挡建筑与临街建筑间的距离不应过大。

英文摘要：

Urban street canyons are always blocked by upstream buildings. To evaluated the block effects on the air flow in a canyon, numerical simulations were conducted to investigate the impacts of the distances between the upstream building and the street canyon （D） on the air environment in the street canyons. In the range of the normal intervals between the buildings, the turbulence intensity, the averaged velocity and the fluctuation of the wind velocity in the street canyons would be decreased with increase of the value of D, and this would lead to increments of the averaged pollutant concentration by 36% within the canyon and by 41% in the near ground region if D increased from 15m to 60m. Therefore, large value of D is not necessary for building design in practice.