城市街区大气流动与汽车尾气扩散的三维数值模拟

道路交通已成为现代城市的主要污染源，利用数学模型预测汽车排放污染物对大气环境的影响成为主要手段。针对一个典型城市街区的大气流动和汽车排放物扩散问题进行三维数值模拟分析，揭示了污染物在不同高度建筑物。不同宽度街道和十字道路所组成的街区峡谷内外的大气流动和污染物迁移扩散特征，同时反映了街道走向的影响。研究表明：由于受街道布局和大气边界层的影响，污染物主要集中在街区峡谷内（特别是近地面附近)难以扩散，易造成局部高浓度污染；由于流场的非均匀性和三维特征，污染物浓度呈现非均匀扩散特性。

3D Numerical Modeling for Airflow and Dispersion of Vehicle Exhaust Gas in Urban Street Block

Vehicular traffic has become a major source of air pollution in urban areas. Mathematical model is an important method for revealing the influence of vehicle emissions on atmospheric environment and 3D numerical modeling analysis for the airflow and dispersion of vehicle exhaust gas has been applied to a typical street block. The airflow and dispersion characteristics of pollutants within the street canyon block composed of different height of buildings, different width of streets, and crossroad were showed. It demonstrated that pollutants were assembled around ground level, and were difficult to be removed and dispersed due to the influence of atmospheric boundary layer, thus it may be easy to result in locally air pollution, and the nonuniform diffusion characteristics of pollutant due to the nonuniform 3D airflow could be observed.