Abstract
Pollutant dispersion in urban areas has been a key concern in densely populated cities because pollutants can negatively impact human health and the environment. Topography and urban obstructions, such as buildings, greatly affect the atmospheric fluid flow, leading to the dispersion process. Street canyons are usually formed in highly populous cities due to the close proximity of buildings to streets to serve commercial purposes. It can also be termed as pollutant traps that exact adverse effects on urban life. Street canyons cause changes in pollutant dispersion, particularly in the case of vehicle exhaust air pollutants, which cannot be transported by the wind owing to the presence of buildings acting as impediments regardless of the wind flow. Hence, it is imperative to completely understand the behavior of pollutants within the confined urban surroundings for further improving the urban air quality. This study explores the effects of street canyons on the busiest street of Dhaka city in Bangladesh. The Reynolds-averaged Navier–Stokes based dispersion model is used to investigate the air quality phenomenon. Building height, width, building distance, and road width have been taken into consideration in the simulation. It is expected that the findings of the current study would be helpful for urban planners and designers of Dhaka city.
Highlights
High air pollutant levels have often been detected in urban street canyons because of increased road traffic discharges and limited air passage
Street canyons cause changes in pollutant dispersion, in the case of vehicle exhaust air pollutants, which cannot be transported by the wind owing to the presence of buildings acting as impediments regardless of the wind flow
The wind flow patterns and pollutant dispersion for the three different kinds of street canyon configurations are studied in detail to figure out the urban-planning strategies to reduce the air pollution inside the street canyon
Summary
High air pollutant levels have often been detected in urban street canyons because of increased road traffic discharges and limited air passage. Numerous research studies have been conducted so far to account for the contribution of each of the significant sources of air pollution that affects the air quality in urban life. It is well-documented that motor vehicle exhaust is one of the major culprits for air pollution in street canyons in most densely populated cities.. Scitation.org/journal/adv dispersion over two separate isolated buildings was carried out by Gousseau et al.13 They employed Reynolds-averaged Navier–Stokes (RANS) and LES models to study the gas dispersion. Pollutant dispersion simulation in urban areas is carried out numerically by employing a RANS based k–ε turbulence model. The wind direction has been assumed to be normal to the street canyon
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