Numerical Simulation Of The Flow Field And Pollution Concentration Field In Street Canyon

With the rapid development of economy and vehicle population,vehicle exhaust pollution becomes a serious problem to urban environment.Field measurements,laboratory-scale physical modeling and computational fluid dynamics(CFD) techniques are common tools adopted to study the wind flow and pollutant distributions in urban street canyons.With the ever-increasing power of computer hardware,numerous sophisticated CFD models have been developed to study the flow field and pollutant transport in street canyons.However,the current studies about the performance of different CFD models used on the research of wind flow and pollutant distributions in urban street canyons are not common.What's more,mainly research on the street canyon structure is the two-dimensional scale,but which does not obviously agree with the fact.Firstly,based on standardκ-εturbulence model,we simulated airflow fields within urban street canyons and validated against Reynolds stress model and wind tunnel results.The numerical simulation results show that the standardκ-εturbulence model is the best choice for studying the wind flow in urban street canyons.Secondly,we performed a numerical investigation of flow and pollutant dispersion within a three-dimensional scale urban area and found that there are a lot of differences between two-dimensional scale and three-dimensional scale numerical simulation results. At last,the dispersion of gaseous pollutants emitted from motor sources was investigated at a group of eight buildings surrounding a square.The analysis of simulation results showed that vehicle emission in the square was easy to disperse and we should integrate dominant wind direction to design such architectural layout in urban planning.