Simulation Study On Atmospheric Wind And Pollutants Dispersion In City

The Air quality of cities is closely related with people's lives, pollutants dispersion which industry process or civil process emitted was the main factor that the air of cities was polluted. Characteristic of city underlying surface was dry, high temperature and rough, atmospheric wind and pollutants dispersion was complicated by complex underlying surface. It is guiding significance to improve the living environment that study mechanism and law of atmospheric environment and pollutant dispersion on heterogeneous underlying surface.This study based on atmospheric dynamic theory, air dispersion theory and numerical calculation theory, atmospheric wind and pollutants dispersion was calculated. Atmospheric dynamic model and pollutants dispersion model on inhomogeneous underlying surface. Through simplify and approximate primitive equations, atmosphere dynamic model on inhomogeneous underlying surface was built: k-εtwo equation model was applied to atmospheric dynamic equations; atmospheric dynamic equations was simplified and approximated by Boussinisq approximation ; convection-diffusion equations was applied to calculated pollutants dispersion. Equations of atmosphere, energy equation, and diffusion equation were coupled, procedure that could calculate wind field and concentration field on complex underlying surface was developed. The procedure was written in FORTRAN language and TECPLOT software as post-processing tool.Through analysis and compare results of simulation, following results are obtained on complex underlying surface: in no wind case,dispersion patterns were mushroom shape; diffusion region of pollutants become narrow as wind speed increases. gradient wind was changed by building, there were eddies at windward side of building and behind the building, going up velocity of airflow reached maximum at front sharp corner of top surface. On the condition of urban heat island effect, the air flow field was wavy, heat island circulation was gradually disappeared as wind speed increases. This study can provide theoretical basis and reference for the process of pollutant diffusion, pollution control, the Emergency Accidents of poisonous gas leakage.