街道峡谷内机动车排放污染物的数值模拟

Numerical study on pollutant dispersion in urban street canyons

针对典型的平顶和坡顶的城市街道峡谷结构,通过求解二维和三维不可压缩N S方程、湍流模型方程及对流扩散方程,数值模拟了街道峡谷内的流场及机动车排放污染物的对流扩散.结果表明,使用二维和三维数学模型所计算的两边为平顶建筑的街道峡谷内污染物浓度不同;而两边为坡顶和平顶建筑的街道峡谷内的背风面污染物的浓度,在相同的气象条件下,三维数学模型数值模拟结果基本一致.

In the present study a numerical model is used for dispersion simulation of vehicle emissions when investigating air quality in street canyons.In a first approach,the two-dimensional street canyon model with the same height for both sides of buildings is adopted when the inflow wind is perpendicular to the street canyon.A second set of calculations using a three-dimensional simulation model of the street canyon with the same inflow wind and geometry as in the two-dimensional street canyon model is performed to investigate the wind flow field and concentration distribution within the street canyon.Comparing the resulting data from the two different models,discrepancies between both models are found for the prediction concentration fields in the street canyon when simulating car exhaust dispersion.