Impact Factors on Airflow and Pollutant Dispersion in Urban Street Canyons and Comprehensive Simulations: a Review

Zhang, Yunwei; Gu, Zhaolin; Yu, Chuck Wah

doi:10.1007/s40726-020-00166-0

Cited by 41 publications

(21 citation statements)

References 120 publications

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“…When the wind blows perpendicularly in a street canyon, two dominating flow phenomena occur in the central part and corners at either end [14,34]. In the simulated results of this study [34], a flow was observed down the windward wall, which traversed up to the top of the leeward wall that was parallel to the wind direction regardless of the road width. This was influenced by the external flow at the top, which led to the formation of a clockwise main vortex driven by the sheer force through the street [68].…”

Section: Changes In Flow According To Vegetation Configurationmentioning

confidence: 63%

“…Previous studies have examined the factors affecting air pollutant distributions along urban streets through wind tunnel tests, numerical simulations, or combinations of experimental methods. In particular, models based on computation fluid dynamics (CFD) have effectively explained the influence of the ratio of the street width to building height, vegetation characteristics, noise barriers or boundary walls, and individual buildings on the flow and diffusion of air pollutants [1,34]. Studies on the effects of vegetation on pollutant concentrations have revealed a relationship among the tree crown size, porosity, leaf area density (LAD), tree height, and planting interval [35][36][37][38][39][40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Vegetation Configuration Models for Managing Particulate Matter along the Urban Street Environment

Jeong

Han

Kim

2022

Forests

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As a green infrastructure component, urban street vegetation is increasingly being utilized to mitigate air pollution, control microclimates, and provide aesthetic and ecological benefits. This study investigated the effect of vegetation configurations on particulate matter (PM) flows for pedestrians in road traffic environments via a computation fluid dynamics analysis based on the road width (four and eight-lane) and vegetation configuration (single-, multi-layer planting, and vegetation barrier). Airflow changes due to vegetation influenced PM inflow into the sidewalk. Vegetation between roadways and sidewalks were effective at reducing PM concentrations. Compared to single-layer planting (trees only), planting structures capable of separating sidewalk and roadway airflows, such as a multi-layer planting vegetation barrier (trees and shrubs), were more effective at minimizing PM on the sidewalk; for wider roads, a multi-layer structure was the most effective. Furthermore, along a four-lane road, the appropriate vegetation volume and width for reducing PM based on the breathing height (1.5 m) were 0.6 m3 and 0.4 m, respectively. The appropriate vegetation volume and width around eight-lane roads, were 1.2–1.4 m3 and 0.8–0.93 m, respectively. The results of this study can provide appropriate standards for street vegetation design to reduce PM concentrations along sidewalks.

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Section: Changes In Flow According To Vegetation Configurationmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Evaluation of Vegetation Configuration Models for Managing Particulate Matter along the Urban Street Environment

Jeong

Han

Kim

2022

Forests

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“…The concentration at the pedestrian level decreased by nearly 42% after half an hour when the steady-state airflow field was the initial field in the time-varying inflow simulation. Therefore, Zhang et al [59,60] concluded that the influence of time-varying inflows was significant and should not be ignored. Table 2 Overview of studies on the effect of time-varying inflows…”

Section: Time-varying Inflowmentioning

confidence: 99%

Review on pollutant dispersion in urban areas-part A: Effects of mechanical factors and urban morphology

Ming

Liu

et al. 2021

Building and Environment

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“…URANS predicted slightly better pollutant concentration than RANS, but since it was not able to capture the fluctuations of the turbulent flow, it was not as numerically efficient as LES. The review by Zhang et al [16] is another good source of information for comparing different methods. Recently, Son et al [14] evaluated wind environments around multiple urban canyons through the k − turbulence termination method that was inspired by the renormalization group (RNG) theory for turbulence parametrization as part of an initial assessment with scopes of further exploration in terms of weather or other coefficients correlating to the wind environment.…”

Section: Introductionmentioning

confidence: 99%

Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City

et al. 2022

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The atmospheric flow and dispersion of traffic exhaust were numerically studied in this work while considering a model street canyon intersection of a city. The finite volume method (FVM)-based large-eddy simulation (LES) technique in line with ANSYS Fluent have been used for flow and pollutant dispersion modelling through the consideration of the atmospheric boundary layer (ABL). Hexahedral elements are considered for computational domain discretization in order to numerically solve problems using FVM-LES. The turbulence parameters were superimposed through a spectral synthesizer in the existing LES model through ANSYS Fluent as part of ’damage control’ due to the unsteady k−ϵ simulation. Initially, the code is validated with an experimental study of an urban street canyon where the width and height ratio is in unity. After validation, a model urban street canyon intersection was investigated in this work. The model shows a high pollutant concentration in the intersecting corner areas of the buildings. Additionally, the study of this model intersection shows a high level of pollutant concentration at the leeward wall of downwind building in the case of increased height of an upwind building. Most importantly, it was realized from the street intersection design that three-dimensional interconnection between the dominating canyon vortices and roof level flow plays a pivotal role in pollutant concentration level on the windward walls. The three-dimensional extent of corner eddies and their interconnections with dominating vortices were found to be extremely important as they facilitate enhanced ventilation. Corner eddies only form for the streets towards the freeway and not for the streets towards the intersection. The results and key findings of this work offer qualitative and quantitative data for the estimation, planning, and implementation of exposure mitigation in an urban environment.

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Impact Factors on Airflow and Pollutant Dispersion in Urban Street Canyons and Comprehensive Simulations: a Review

Cited by 41 publications

References 120 publications

Evaluation of Vegetation Configuration Models for Managing Particulate Matter along the Urban Street Environment

Evaluation of Vegetation Configuration Models for Managing Particulate Matter along the Urban Street Environment

Review on pollutant dispersion in urban areas-part A: Effects of mechanical factors and urban morphology

Large-Eddy Simulation of Airflow and Pollutant Dispersion in a Model Street Canyon Intersection of Dhaka City

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