Abstract
Observation data show that natural wind has a characteristic of regular time-variation in speed and direction. However, the time-varying inflow conditions are usually simplified as a constant wind profile in simulations on airflow and pollutant dispersion in urban street canyons and/or building cluster. The study on characteristics of urban canopy layer (UCL) flow under time-varying inflow conditions should be further contribute to the understanding of pollutant and energy transport processes in the urban atmospheric environment. In the current work, typical studies on air flow and pollutant dispersion in urban street canyons and building array are reviewed. The time-varying upstream inflows could commonly enhance the transportation of pollutant and energy in actual UCL. Studies have revealed that the variation of natural inflow conditions could be one of the primary factors that influencing the transport efficiency of pollutant in urban street canyons. Perspectives on methods in performing the time-varying inflow conditions are provided as well. Gradual and/or stepped variation of wind data would be expected in numerical simulations.
Highlights
Due to effects of global climate change and rapid urbanization, there has been an increasing interest in the urban wind environment and pollutant dispersion for a long time
The time-varying inflow conditions are usually simplified as a constant wind profile in simulations on airflow and pollutant dispersion in urban street canyons and/or building cluster
The study on characteristics of urban canopy layer (UCL) flow under time-varying inflow conditions should be further contribute to the understanding of pollutant and energy transport processes in the urban atmospheric environment
Summary
Due to effects of global climate change and rapid urbanization, there has been an increasing interest in the urban wind environment and pollutant dispersion for a long time. In the recent 30 years, the analysis of urban wind environment has been successfully applied in various fields such as pedestrian wind comfort assessment (Janssen et al, 2013), pollutant dispersion prediction (Xia et al, 2012; Scungio et al, 2013; Nikolova et al, 2014), wind load determination (Solari and Pagnini, 1999), natural ventilation analysis (Hang et al, 2013) for building and urban planning policy decision Various methods such as numerical simulation, wind tunnel simulation and in-situ observations have been used. To investigate the air flow, turbulence and pollutant dispersion characteristics within urban street canyons under natural background wind conditions, the time-varying inflow conditions should be considered. This paper reviews the characteristic of natural background wind and the effect of inflow conditions on air flow and pollutant dispersion within urban street canyons, with a perspective on methods in performing the time-varying inflow conditions
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