城市对称街道峡谷气流及污染物扩散特征的研究

与风洞实验的对比表明数值模拟能较好地预测街道峡谷浓度场。研究了宽、窄两种峡谷（高宽比范围为0．17～3．25）的内部流场和浓度场。表明：当高宽比大于1时，随着高宽比的增加，峡谷内旋涡数逐渐增多，污染物浓度也随着旋涡的变化而变化；当高宽比小于1时，峡谷内由一个旋涡演变为两个方向相反的旋涡，随着高度的进一步减小，两个旋涡开始左右分离，其浓度也随着旋涡的变化而变化。当旋涡为顺时针时，使得背风面污染物浓度出现显著上升的趋势，而当旋涡为逆时针时，会使得迎风面的污染物浓度出现显著上升的趋势。总体看来，随着建筑物高度的增加，污染物难以扩散，从而使峡谷近地面处的污染物浓度增大。

Patterns of airflow and vehicular emission pollutant dispersion in symmetrical urban street canyons

By comparing with the wind tunnel experimental results, the numerical simulation can well predict the concentration field in street canyon. The wind flow structure and concentration in wide and narrow symmetrical street canyons were studied. It was shown that when the ratio of building height to street width is larger than 1, the number of vortices increases and the concentration varies with the number of the vortices. When the ratio is less than 1, the number of vortices varies from one into two with opposite directions, and these vortices split separately with further decreasing of the ratio. The concentration changes with the number of the vortices. When the vortex is clockwise, the concentration at leeward side is larger than that at windward side; when the vortex is anticlockwise, the concentration at windward side is larger than that at leeward side. In a word, with increasing the height of building, it makes more difficult to disperse the pollutants and more concentration near the ground level.