Dispersion study in a street canyon with tree planting by means of wind tunnel and numerical investigations – Evaluation of CFD data with experimental data

Gromke, CB Christof; Buccolieri, Riccardo; Sabatino, Silvana Di; Ruck, Β.

doi:10.1016/j.atmosenv.2008.08.019

Cited by 368 publications

(143 citation statements)

References 30 publications

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“…Balczo et al, 2009;Buccolieri et al, 2011Buccolieri et al, , 2009Gromke and Ruck, 2012Gromke, 2011;Gromke et al, 2008;Li et al, 2013;Moonen et al, 2013;Salim et al, 2011;Vos et al, 2013;Wania et al, 2012), qualitative and not only quantitative changes in the flow field were observed at the neighborhood scale. The qualitative changes indicate on the one side the necessity to perform studies at the urban neighborhood rather than at the street canyon scale and on the other side to account for avenue-trees, or more general all types of vegetation typical for built-up environments, in microscale urban air quality studies.…”

Section: Discussionmentioning

confidence: 91%

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Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level

Gromke

Blocken

2015

Environmental Pollution

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120

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a b s t r a c tFlow and dispersion of traffic-emitted pollutants were studied in a generic urban neighborhood for various avenue-tree layouts by employing 3D steady RANS simulations with the realizable k-ε turbulence model. In comparison to the tree-free situation quantitative and qualitative changes with flow reversal in the wind field were observed. Low to moderate increases (<13.2%) in the neighborhood-averaged pollutant concentration were found at pedestrian level. An approximately 1% increase in the neighborhood-averaged concentration was obtained with each percent of the street canyon volumes being occupied by vegetation for occupation fractions between 4 and 14%. The overall pattern of concentration changes relative to the tree-free situation was similar for all avenue-tree layouts. However, pronounced locally restricted decreases or increases in concentration (À87 to þ1378%) occurred. The results indicate the necessity to account for existing or planned avenue-trees in neighborhood scale dispersion studies. Their consideration is prerequisite for reliable urban air quality assessment.

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Section: Discussionmentioning

confidence: 91%

“…(Balczo et al, 2009;Buccolieri et al, 2009;Gromke and Ruck, 2012Gromke, 2011;Gromke et al, 2008;Li et al, 2013;Moonen et al, 2013;Salim et al, 2011). The reason for this is the flow resistance of tree crowns which slows down the wind and reduces the air exchange between the street canyon and surrounding.…”

Section: Introductionmentioning

confidence: 99%

Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level

Gromke

Blocken

2015

Environmental Pollution

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120

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“…Vegetation type, height, and thickness can all influence the extent of mixing and pollutant deposition experienced at the site. The built environment also matters greatly -air flow and impacts of trees are substantially different for a street canyon environment than an open highway environment (Buccolieri et al, 2009(Buccolieri et al, , 2011Gromke et al, 2008). Uncertainty remains concerning the degree to which vegetation reduces (or increases) pollutant concentrations in the near-road environment under varying meteorological conditions and vegetation characteristics.…”

Section: Introductionmentioning

confidence: 99%

Field assessment of the effects of roadside vegetation on near-road black carbon and particulate matter

Brantley

Hagler

Deshmukh

et al. 2014

Science of The Total Environment

153

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• Vegetation barriers altered near-road black carbon concentrations.• Vegetation reduced downwind black carbon concentrations by approximately 12%.• Downwind fine and coarse particle concentration were unaffected by vegetation.• Black carbon gradients more gradual behind vegetation compared to a clearing. a b s t r a c t a r t i c l e i n f o One proposed method for reducing exposure to mobile source air pollution is the construction or preservation of vegetation barriers between major roads and nearby populations. This study combined stationary and mobile monitoring approaches to determine the effects of an existing, mixed-species tree stand on near-road black carbon (BC) and particulate matter concentrations. Results indicated that wind direction and time of day significantly affected pollutant concentrations behind the tree stand. Continuous sampling revealed reductions in BC behind the barrier, relative to a clearing, during downwind (12.4% lower) and parallel (7.8% lower) wind conditions, with maximum reductions of 22% during the late afternoon when winds were from the road. Particle counts in the fine and coarse particle size range (0.5-10 μm aerodynamic diameter) did not show change. Mobile sampling revealed BC concentration attenuation, a result of the natural dilution and mixing that occur with transport from the road, was more gradual behind the vegetation barrier than in unobstructed areas. These findings suggest that a mature tree stand can modestly improve traffic-related air pollution in areas located adjacent to the road; however, the configuration of the tree stand can influence the likelihood and extent of pollutant reductions.Published by Elsevier B.V.

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“…CFD modelling may indeed be useful to investigate the details of flow characteristics at micro scale but it requires considerably large capacity of computer resources if adopted for large spatial scales (e.g., city). Modelling studies dealing with the air flow in areas with complex geometries are abundant (Di Sabatino et al, 2007;Gromke et al, 2008;Kumar et al, 2008a;Narita et al, 2008;Buccolieri et al, 2009;Abdulsaheb and Kumar, 2010;Vos et al, 2012b). However despite the large scientific interest and contribution to the topic of UFP for the last decade, the ultrafine particles still remain an area with open questions and even contradictory opinions.…”

Section: Introductionmentioning

confidence: 99%

Modelling the Mixing of Size Resolved Traffic Induced and Background Ultrafine Particles from an Urban Street Canyon to Adjacent Backyards

Nikolova

Janssen

Vos

et al. 2014

Aerosol Air Qual. Res.

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By means of numerical simulations the aims of this study are as follows: (1) to investigate the dispersion and mixing of ultrafine particles (UFP) with pre-existing size resolved UFP in a street canyon and its vicinity with the ENVI-met 3D microscale model; (2) to show the effects of boundary conditions, like wind direction and traffic emissions, on the UFP concentration in the near vicinity; and (3) to evaluate the importance of deposition and coagulation at the street scale. The decrease in UFP concentration in nucleation mode particles (diameter < 30 nm) and Aitken mode particles (diameter between 30-100 nm) downwind of the street canyon is caused by the large differences in the size distributions of the emissions and the background. Based on the wind direction and traffic emissions, the UFP concentration over the rooftop increases by 23% for the South-West wind up to 165% for the Northern wind. The background distribution for the South-West wind direction remains mono-modal, with a peak in the Aitken mode as a result of the relatively low contribution of advected particles from the street canyon. For the Northern wind the background size distribution transforms to a bi-modal distribution, with peaks in the nucleation and the Aitken modes as a result of the high UFP concentration advected from the boulevard. The overall effect of deposition and coagulation on the UFP is negligible for the cases considered in this study. Overall, deposition is more efficient and faster than coagulation in removing particles, and especially those in the nucleation mode.

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Dispersion study in a street canyon with tree planting by means of wind tunnel and numerical investigations – Evaluation of CFD data with experimental data

Cited by 368 publications

References 30 publications

Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level

Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level

Field assessment of the effects of roadside vegetation on near-road black carbon and particulate matter

Modelling the Mixing of Size Resolved Traffic Induced and Background Ultrafine Particles from an Urban Street Canyon to Adjacent Backyards

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