Use The Meso-Microscale Coupling Model Simulation Pollutant Field Dispersion In The City Streets

Urban environment of the atmospheric pollutants spread by complex structure around the wind place control. The wind "wash" and because buildings under the existing air caused turbulence intensity increased, strongly influenced by not only the average wind field, also affect diffusion parameters. Because the city streets this relatively narrow streets space is a unique structure, special underlaying surface and micro climate characteristics, so led to the formation of near-earth inversion layer, killing local high levels of atmospheric pollution, study of pollutants in the city streets flow field distribution in realistic meanings.This study USES the computational fluid dynamics software Fluent in ankang city, sometime city streets as the research object, the establishment of physical model and three-dimension turbulent model, simulate different geometric structure in the city streets under different wind speed of air flow NaFeng field neighborhoods, and one of the main ingredients in stenches for main sources-methanthiol contaminant distribution on the simulation. The simulation results show that the buildings on the block, wind velocity grads outside will reach the maximum; In building the place such as the corner to flow velocity and direction all occurred a drastic change; In the neighborhood, easy form vortex; Within the building group formed smaller vortex, easy; Through the flow field analysis, can see wind flow on the influence of filth diffusion. In a narrow type of streets, due to the high buildings prevents the windward surface effect, streets of negative pressure and large exist inside the vortex pcis emissions of pollutants. And in open type of streets of contaminant, wind of little influence. So in city streets in the layout should be avoided in the large building wind, or avoid in existing pollution sources of the establishment of the narrow neighborhoods.Through the Fluent software accord zone pollution logistics field distributions in simulated, the result show, visual reflects the whole neighborhood wind field distribution and pollutant concentration change trend, the simulation results in the research of urban streets for the architectural layout, road construction, transportation planning and traffic control, pollution control is very significant.