基于BSMPKU的高分辨率大气扩散数值模拟研究

High resolution numerical simulation of the atmospheric dispersion based on BSMPKU

为了检验北京大学街区尺度模式BSMPKU(Block Scale Model of Peking University)在城市大气环境研究中的适用性,首先利用Thompson风洞试验的数据集对BSMPKU模式进行了验证,并将其模拟结果与Open FOAM(Open Source Field Operation and Manipulation)的模拟结果进行比较,然后将BSMPKU模式应用在复杂的实际建筑物群中,进行了3种不同交通线源排放的理想数值模拟研究。结果表明:1)对于单个建筑物,随建筑物宽度增加,建筑物迎风面回流区和建筑物背风面的尾流涡区范围增大;2)BSMPKU和Open FOAM对单个建筑物周围的流场及浓度场有较好的模拟能力;3)与基于高斯扩散理论的AERMOD相比,BSMPKU和Open FOAM能更好地模拟出建筑物周围的浓度场,但两个模式的模拟结果都与实测值存在一定误差;4)在实际小区中,受建筑物群影响,建筑物群内的流场分布比较复杂,大部分地区风速大幅下降,建筑物群内污染物浓度场的分布受排放源位置和走向的影响很大;5)BSMPKU能较好地模拟出实际城区的流场和浓度场分布,具有一定模拟和预报复杂城区污染物扩散过程的能力。

The present article is inclined to estimate the ability of the so-called Block Scale Model of Peking University BSMPKU in simulating and forecasting the airflow and air pollutant dispersion in the real urban areas. To validate the numerical results of BSMPKU,we have,first of all,adopted the Thompson dataset from the wind tunnel to compare the gap in the simulation results between the two Computational Fluid Dynamics（ CFD） model,BSMPKU and the OpenF OAM（ Open Source Field Operation and Manipulation）. And,then,we have been trying to apply the said BSMPKU model to the complex real urban areas for simulating the airflow and dispersion pattern of the pollutants released from the three hypothetical traffic line sources. The results of our simulation show that：（ 1） The reverse area in front of the windward side and recirculation region behind the leeward side extend with the broadening of the width of an isolated building;（ 2） BSMPKU and OpenF OAM function well in simulating the wind field and the concentration field around the said isolated building,on the top of whose roof vortex can be clearly identified in the wind field simulated by OpenF OAM;（ 3） As compared to the AERMOD（ American Meteorological Society / Environmental Protection Agency Regulatory Model）,a Gaussian plume model,the BSMPKU and OpenF OAM we were using helped to forecast the concentration much better,especially in the location and at the peak of the concentration value,whereas there might still exist some errors between the simulation results of the two models and the data gained from the experiments;（ 4） The wind field shows that the complicated features in the building block area due to the effects of the building blocks,for example,the wind velocity tends to be made slower within the building blocks area. What is more,the vortexes that are generated in the building block area are not merely,but quite a many,which result in a very bad condition for the dispersion of the air pollutants. Moreover,it is the location and the direction of the pollution source generated in the building block that could produce very great impacts on the pollution concentration,whose peak data of the concentration around the source tended to increase dramatically when the line source was passing through the building clocks;（ 5） The BSMPKU model that functions well over the real urban area enjoys the strong power of simulating and forecasting the dispersion in the complicated real urban area.