A Large Eddy Simulation on the Effect of Building on Atmospheric Pollutant Dispersion
The effect of buildings on wind flow fields plays a very important role in urban meteorology and air pollutant dispersion. To understand the urban flow characteristics will help us improve the understanding and prediction in micro/local scale meteorology. Large eddy simulation is one of the most sophisticated methods. A large eddy simulation model is used to simulate the flow structure around a bluff building. TKE (Turbulent Kinetic Energy) sub-grid closure scheme is employed in the model. The numerical simulation results are compared with the wind tunnel experiment-CEDVAL (Compilation of Experimental Data for VALidation of microscale dispersion models). The results are compared both in whole and in detail. The large eddy simulation model can describe the reverse flow a-bove the building top and the cavity structure well. The numerical simulated horizontal and vertical wind speeds are compared with the physical simulation results as well. It shows that the flow characteristics around the building can be illustrated in detail by the large eddy simulation model. Based on the flow results, a Largarian particle model is employed to simulate the atmospheric pollutant dispersion around the building. The large eddy simulation model can provide detailed and reliable wind and turbulence fields, which can help the dispersion model describe the air pollutant diffusion better. A series of cases of air pollutant dispersion from a virtual source are simulated by the numerical models to understand how the source location impacts the pollutant dispersion around a bluff building. The results show that a minute change of the source location may lead to a great change of the pollutant distribution because the distortion of flow due to the effect of the building, especially for the surface pollutant concentration in the wake are-a. In the first three cases the source location is set above the building roof. When the point source location is set at Z/H =1. 05 (H is the building height), the pollutant is carried by the downwash stream of the cavity structure and the concentration is largest in these three cases. When the point source location is changed from Z/H= 1.05 to Z/H= 1. 25, most of the pollutant will skip the cavity flow behind the building and the surface concentration in the wake area decreases greatly, the peak value of the surface concentration is behind the wake. When the source is moved to Z/H=1. 28, most of the pollutant is cleaned from the simulation domain, the surface concentration is nearly zero. When the source is in the wake behind the building, the pollutant stays in local area causing a high surface concentration. A great part of pollutant will also be carried downward due to the circulation flow behind the building and cause a great surface pollutant concentration.
large eddy simulationbuildingsurban environmentatmospheric pollutant dispersionair flow
国家科技期刊平台
NSTL
万方数据
维普
