Analysis of ventilation efficiency indices inside a local domain within an urban area using two building model

ABSTRACT: This paper deals with the determination of the ventilation efficiency (VE) indices, Purging Flow Rate, Visitation Frequency, and Staying Time of air pollutants, inside a domain located within an urban area. For the purpose of study, a wind environment of 100 x 100 x 75 m volume was considered and a two building model inside was adopted to perform the calculations. A void was constructed by a central street with one building on each side. Two parameters were selected to evaluate the VE indices; the first one was the street width, while the second parameter was the height of the upwind building. In all cases of the present study, the applied wind direction was assumed normal to the street direction. The evaluation of the VE indices were carried out based on the average pollutant distribution inside the domain. Results of the study showed that, both the street width and the upwind building height have great effects on the VE indices, as they can be considered the tools which control the air quality inside urban domains.