Research On The Pollutant Diffusion Of Traffic Canyon Influenced By Urban Street Space

Urban Traffic Canyon is especially specified that the narrow space like canyon pattern isenclosed with urban roads and adjacent buildings in both sides. As a significant section of theurban traffic system, the quality of Microenvironment of Urban Traffic Canyon could beexerting enormous effects on the comfort of outdoor environment, the physical and mentalhealth of the people outdoor and even the indoor air quality of adjacent buildings. Therefore,it is imperative to understand and grasp perfectly the diffusion mechanism of pollutants inUrban Traffic Canyon in order to improve the environment of Traffic Canyon in anappropriate way involved in architecture design etc.Real-time changing data about various influence parameters related to the pollutantdispersion in typical traffic canyon of Xi’an in a typical winter climate could be acquiredeasily through the method of practical testing. Through the comparison of testing data, thediffusion law and influence mechanism of pollutants in Traffic Canyon can be analyzed inorder to provide an empirical evidenced foundation and a simply basis for the establishmentof pollutant dispersion model of Traffic Canyon. On this basis, a typical three-dimensionalmodel associated with pollutant dispersion has been precisely established, besides, thereasonable hourly dynamic temperature boundary conditions and rational local boundaryconditions of wind speed in urban canopy layer have been utilized correctly, the wholesimulation program for the calculation of three-dimensional pollutant dispersion has beencompiled completely. Lastly, three-dimensional model belonged to pollutant dispersion hasbeen verified wonderfully through the comparison of simulation results and testing results.The architectural parameters of pollutant-dispersed model would be changedsuccessively in a numerical simulation way, comparing the carbon monoxide distribution inthree different aspect ratio：1:1,1:1.3and1:1.5, and three distinctive roof patterns: bothpitched roofs, one pitched roof in the leeward side and one pitched roof in the windward side, respectively. The variation of carbon monoxide concentration in both leeward side andwindward side under various aspect ratio and roof patterns conditions could be summarizedthrough the final simulation results. The simulation data indicates that there is a huge amountof pollutant when aspect ratio is1:1.3, the corresponding carbon monoxide concentrationarrives at the top of three conditions, which would be definitely detrimental to both the healthof pedestrians and the air quality of adjacent buildings, at the same time, the pattern of onepitched roof in the leeward side would be absolutely beneficial to the diffusion of the trafficcanyon pollutant. Eventually, based on the diversity law of pollutant dispersion in differentcanyon patterns, optimization strategies in terms of urban street and adjacent buildings couldbe proposed theoretically.In this essay, research on influence mechanism of pollutant dispersion in urban trafficcanyon in the fields of urban street space has been fulfilled through both testing method andnumerical simulation method，aiming to provide a set of fundamental theory for the authenticscientific space layout of traffic canyon design.