Effects of street orientation on dispersion at or near urban street intersections

Wang, X.; McNamara, Kevin

doi:10.1016/j.jweia.2007.02.021

Cited by 23 publications

(12 citation statements)

References 6 publications

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“…The influence of such updrafts on the dispersion of a traffic related pollutant was recently discussed by . The field study supports recent modelling and wind-tunnel intersection studies Wang and McNamara 2007;Carpentieri et al 2009;Soulhac et al 2009) for oblique reference flows towards the north. However, the behaviour of the intersection flow is observed to be much more complicated for similar southward reference flows with a high degree of variability, due mainly to the asymmetry in the intersection building geometry.…”

Section: Discussionsupporting

confidence: 86%

“…The results support recent wind-tunnel flow visualisation and CFD investigations for idealised intersection configurations Wang and McNamara 2007;Carpentieri et al 2009;Soulhac et al 2009). These studies show that, for oblique above roof wind directions, interaction between channelling in both street canyons occurs at the intersection, but might also be superimposed by both vertical and horizontal vortex structures.…”

Section: Oblique Flows Towards the North (+60 • )supporting

confidence: 87%

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In-Street Wind Direction Variability in the Vicinity of a Busy Intersection in Central London

Balogun

Tomlin

Wood

et al. 2010

Boundary-Layer Meteorol

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We present results from fast-response wind measurements within and above a busy intersection between two street canyons (Marylebone Road and Gloucester Place) in Westminster, London taken as part of the DAPPLE (Dispersion of Air Pollution and Penetration into the Local Environment; www.dapple.org.uk) 2007 field campaign. The data reported here were collected using ultrasonic anemometers on the roof-top of a building adjacent to the intersection and at two heights on a pair of lamp-posts on opposite sides of the intersection. Site characteristics, data analysis and the variation of intersection flow with the above-roof wind direction (θ re f ) are discussed. Evidence of both flow channelling and recirculation 123 490 A. A. Balogun et al. was identified within the canyon, only a few metres from the intersection for along-street and across-street roof-top winds respectively. Results also indicate that for oblique rooftop flows, the intersection flow is a complex combination of bifurcated channelled flows, recirculation and corner vortices. Asymmetries in local building geometry around the intersection and small changes in the background wind direction (changes in 15-min mean θ re f of 5 • -10 • ) were also observed to have profound influences on the behaviour of intersection flow patterns. Consequently, short time-scale variability in the background flow direction can lead to highly scattered in-street mean flow angles masking the true multi-modal features of the flow and thus further complicating modelling challenges.

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Section: Discussionsupporting

confidence: 86%

Section: Oblique Flows Towards the North (+60 • )supporting

confidence: 87%

In-Street Wind Direction Variability in the Vicinity of a Busy Intersection in Central London

Balogun

Tomlin

Wood

et al. 2010

Boundary-Layer Meteorol

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“…Vegetation barriers can reflect and deflect approaching air flows, which lead to occurrences of more complicated vortices in urban street canyons. As concluded by previous studies, these vortices can enhance the recirculation of pollutants inside a street canyon (Nazridoust and Ahmadi, 2006;Wang and McNamara, 2007). In the vegetation-free case illustrated in Fig.…”

Section: Effects Of Vegetation Barriersupporting

confidence: 63%

The impacts of roadside vegetation barriers on the dispersion of gaseous traffic pollution in urban street canyons

Lü

et al. 2016

Urban Forestry & Urban Greening

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“…The construction of high rise buildings to cater for growing populations has led to a deterioration in air quality in urban streets and the development of the urban heat island (UHI), as canyons with high aspect ratios reduce the rate of air exchange between roof and the street, leading to trapped air at street level [4][5][6]. Other researchers concur with these findings, additionally identifying vehicular turbulence [7][8][9][10] and the layout and orientation of a street [11,12] as other influential parameters that effect pollutant dispersion in urban canyons.…”

Section: Introductionmentioning

confidence: 91%

Numerical modelling of the passive control of air pollution in asymmetrical urban street canyons using refined mesh discretization schemes

Gallagher

Gill

McNabola

2012

Building and Environment

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This study evaluates the potential of passive controls in asymmetrical street canyons to reduce personal exposure to air pollutants on footpaths. A passive control in the form of a low boundary wall (LBW) may act as a baffle within a street canyon, producing modified airflow patterns and increase pollutant dispersion at street level. This numerical modelling study assessed the spatial distribution of concentrations of a tracer pollutant in a street canyon. Concentrations were measured along the centre of both footpaths at breathing height to determine the percentage difference between pollutant concentrations in canyons with and without passive controls. The investigation assessed asymmetrical street canyons of different building height ratios (H 1 /H 2 ratio ranging from 0.5-1.5 in 0.1 intervals) in perpendicular wind conditions. The results indicated that the H 1 /H 2 ratio affects pollutant dispersion and the implementation of a passive control can reduce the pollutant concentration on the footpaths. The percentage difference in concentrations induced by the presence of footpath LBWs ranged from an increase of up to 19% to a reduction of 30% on the leeward footpath, with reductions between 26% and 50% on the windward footpath with varying H 1 /H 2 ratios. Comparing the results to a central LBW configuration identified the creation of two distinct

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Effects of street orientation on dispersion at or near urban street intersections

Cited by 23 publications

References 6 publications

In-Street Wind Direction Variability in the Vicinity of a Busy Intersection in Central London

In-Street Wind Direction Variability in the Vicinity of a Busy Intersection in Central London

The impacts of roadside vegetation barriers on the dispersion of gaseous traffic pollution in urban street canyons

Numerical modelling of the passive control of air pollution in asymmetrical urban street canyons using refined mesh discretization schemes

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