城市街谷与上游阻挡建筑最不利间距的研究

采用数值模拟的方法，研究了街谷内上风建筑与上游阻挡建筑的间距（D），即上游建筑间距，对街谷内空气流动特性和气态污染物分布规律的影响.模拟结果表明，街谷内迎风区的气流速度基本不随D的变化而变化，而背风区和中心区的气流速度随着D的增加呈现先减小后增大的趋势，并在D=90m时，气流速度达到最小值.相应地，在D=90m时街谷内污染物浓度最高，表明D存在最不利值，在城市规划中应尽可能避免该间距.当D大于90m时，D越大，污染物浓度越低，而D小于90m时，D越小，污染物浓度也越低，可以同时实现节约用地和减小交通污染的目的.

Studies on the most unfavorable distance between the upstream building and the windward building in street canyons in urban area

Numerical simulations were conducted to investigate the influence of the distance between the upstream building and the downstream building in street canyons (D) on characteristics of air flow and distributions of gaseous pollutants in the canyons. The simulation results showed that the wind velocities in the windward regions in the canyons did not change with the change of D. However, the wind velocities in the leeward and central regions decreased first and then increased with the increase of D, and the minimum value occurred when D=90m. Correspondingly, the peak concentration of the pollutant in the canyons appeared at the same D, which indicated the most unfavorable value of D existed. In urban planning, it should be avoided as far as possible. When D was more than 90m, the larger the D was, the lower the pollutant concentration would be. When D was less than 90m, the smaller the D was, the lower the concentration would be, which could be benefit for both land-saving and traffic pollution reduction.