Study On Mechanism Of Gas Flow And Pollutant Dispersion Around The Buildings

The number of cars has increased dramatically as the development of the cities. The height and density of the buildings are also increasing. Emission from automobiles has become a major air pollution source in cities, which seriously affects people’s health. Therefore, the study on the diffused situation of atmospheric pollutants around the buildings is important.The main component of automobile emission is nitrogen oxides. It is inconvenient to measure the concentration of pollutants in complex flow field, and the workload is very large in practice. Therefor, CFD (Computational Fluid Dynamics) approach is adopted to get the distribution of the air pressure, velocity and pollutants around the buildings. The present work mainly includes the following several aspects:The influencing factors on flow and concentration distribution fields of monomer building are investigated, which include the inlet velocity, source location and emission intensity. Simulation results show that when the characteristic of pollution is determined, the greater the inlet velocity, the more beneficial to the diffusion of atmospheric pollutants is. When the inlet velocity is constant, the closer to building, the greater the emissions intensity and the higher local concentration of pollutants are.When residential quarters are built, it is possible to stay away from sources of pollution and the wind blows from the buildings to sources within the most period of a year.The effects of double building layout and the height difference on the flow field and the concentration field have been studied. When the buildings are the same height and arranged front and back, the pollutant concentrations in the upward and downward sites are increase by increasing of the distance between the two buildings. When the buildings are arranged left and right, there is a minimum in the symmetry region of center in the whole calculated area, and the greater the distance, the smaller the minimum is.When the buildings are not the same height, the lower the front building, the higher the concentration of pollutant in the windward side is.When the residential area is planned, the height of the building can be appropriately arranged to achieve the best flow to get residents away from pollution.The distribution of pollutant concentration for three kinds of construction layouts has been studied as well. It is important to note that when buildings are arranged in enclosing style, the concentration of pollutants in enclosed region is lower than that in other regions. It shows that the concentration of pollutants in enclosed area becomes lower by reducing the distance between adjacent buildings appropriately.In the summary, the results obtained in the present study will provide a theoretical basis to improve the layout of the buildings and to reduce the impact of air pollutants on the health of residents.