城市交通十字路口处污染物分布数值模拟

运用描述湍流运动的k-ε双方程模型,模拟计算某城市以公路为线性污染源十字路口处在两种不同风向影响下流场和浓度场分布。方案一中,气流绕过建筑物时在建筑物后会形成明显的涡流,污染物容易在此附近聚集。高浓度带位于两排建筑物之间靠外侧,最大达2.9440μg/m3。方案二中,由于建筑物的位置与风向的关系,气流在建筑物背面形成的涡流不明显,后排建筑物背风面附近以及建筑物之间下部附近的风速较小,易形成高浓度带。高浓度带主要位于下部两建筑物之间一带,以及后排建筑物背风向附近,最大达2.6402μg/m3。方案二明显更有利于污染物的扩散。因此,风向倾斜进入建筑群时,湍流作用减弱,风的迁移作用增强,有利于污染物的扩散。在实际中若建筑物迎风向的表面形状接近梭形,则可促进风对污染物的扩散作用,从而改善建筑物周围的环境空气质量。

Numerical Simulation of Contaminant Distribution at Urban Traffic Cross

k-ε two equation model which describes turbulent movement was used to simulate and calculate the flow field and concentration field distribution in effect of two different kinds of wind direction at the crossroad in a city with road as line pollutants source. In program I,airflow will form obvious vortexes behind the building when airflow circle around a building and pollutants will easily get together. High concentration zone is located where outside between two buildings and up to 2.9440μg/m3. In program II,airflow will not form obvious vortexes because of relation between buildings location and wind direction. Wind speed that is located about buildings rear leeward and between buildings underside is lower,so where is favor to form high concentration zone. High concentration zone is located where underside between two buildings and up to 2.6402μg/m3. The program II is obviously favorable for pervasion of pollutants. When wind into buildings at the direction of slant,the effect of turbulence is decreased and effect of transference is increased,which is favorable to pervasion of pollutants. The exterior windward shape of buildings near patrol will improve the effect of wind to pollutants pervasion and upgrade quality of atmospheric environment around the buildings.