Effects of envelope features on wind flow and pollutant exposure in street canyons

Cui, Dongjin; Li, Xingdi; Du, Yaxing; Mak, Cheuk Ming; Kwok, K.C.S.

doi:10.1016/j.buildenv.2020.106862

Cited by 29 publications

(7 citation statements)

References 35 publications

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“…Moreover, we assumed the following: the near-road buildings were residential, and only a microenvironment of j= 1 (indoor at home) was considered to assess the personal intake fraction for the local residents. Bri,j and Δti,j are the average volumetric breathing rate (m 3 /s) [51] (Table A1) and time spent (s) for individuals in the ith population group in the jth microenvironment [52] (Fig. A1(a)), respectively.…”

Section: Personal Intake Fraction (P_ If)mentioning

confidence: 99%

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The effects of lateral entrainment on pollutant dispersion inside a street canyon and the corresponding optimal urban design strategies

Zhang

Wen

et al. 2021

Building and Environment

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Section: Personal Intake Fraction (P_ If)mentioning

confidence: 99%

“…A1(a)), respectively. Pi is the total number of people exposed in the ith population group, which can be further calculated by the demographic structure (herein, taking Shenzhen, China, as an example for this study [52], Fig. A1(b)).…”

Section: Personal Intake Fraction (P_ If)mentioning

confidence: 99%

The effects of lateral entrainment on pollutant dispersion inside a street canyon and the corresponding optimal urban design strategies

Zhang

Wen

et al. 2021

Building and Environment

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“…Previous studies reveal that the street canyon structure has a positive effect on airflow circulation inside the canyon (Issakhov et al 2020 ; Cui et al 2021 , 2020 ; Reiminger et al 2020 ; Llaguno-Munitxa et al 2017 ; Huang et al 2020 , 2022 ; Zhi et al 2020 ). The asymmetric street structure results in weak canyon ventilation capacity, especially in the step-down canyon (Assimakopoulos et al 2003 ; Gallagher et al 2012 ; Sin et al 2022 ; Reiminger et al 2020 ).…”

Section: Introductionmentioning

confidence: 99%

Evaluation on ventilation and traffic pollutant dispersion in asymmetric street canyons with void decks

Sin

Cui

Jon

et al. 2023

Air Qual Atmos Health

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With continuous global warming, growing urban population density, and increasing compactness of urban buildings, the “void deck” street canyon design has become increasingly popular in city planning, especially for urban streets located in tropical areas. Nevertheless, research on traffic pollutant dispersion in street canyons with void decks (VDs) is still at its early stage. This study quantitatively evaluates the effects of void deck height and location on the canyon ventilation and pollutant dispersion in asymmetric street canyons with void decks, and the pollutant exposure risk level for pedestrians and street dwellers. Void decks introduce more fresh air, thereby greatly improving the ventilation properties of the asymmetric canyon. The air exchange rate ( ACH : 147.9%, 270.9%) and net escape velocity ( NEV *: 416.7%, 915.8%) of the step-up and step-down canyons with VDs (3 m high at full scale) at both buildings are higher than those of regular asymmetric canyons. Moreover, the mean dimensionless pollutant concentration ( K ) on the building wall and pedestrian respiration plane in which VDs are located stands at a low level, because pollutants are removed by the airflow entering or exiting through the void decks. Increased VD height (4.5 m at full scale) enhances the strength of airflow flowing into and out of the canyon, significantly increasing ACH (177.3%, 380.9%) and NEV * (595.2%, 1268.4%) and decreasing the mean K on both pedestrian respiration planes and canyon walls. In particular, the K values on both pedestrian respiration planes and both walls are almost zero for the canyons with VDs at both buildings. Therefore, among the three VD locations, both VDs provide the best living environment for pedestrians and near-road residents. These findings can help to design urban street canyons for mitigating traffic pollution risk and improving ventilation in tropical cities.

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“…These small appurtenances are usually designed to provide everyday convenience (such as balconies), change the local wind environment (such as wind walls), improve the local thermal environment (such as overhangs), or change the local pressure [22]. Murena and Mele [23], Cui et al [24], and Zheng et al [25] conducted CFD simulations with a RANS model to investigate the effects of envelope features on the mean flow and pollutant dispersion in deep street canyons. They found that balconies and overhangs obstruct the airflow from penetrating the bottom of the canyon, increasing the accumulation of pollutants there.…”

Section: Introductionmentioning

confidence: 99%

Turbulence and Pollutant Statistics around a High-Rise Building with and without Overhangs

Jiang,

Wu,

2023

Atmosphere

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Wind flow around an isolated building is highly turbulent. Facade appurtenances can further increase the complexity of the flow, which strongly affects the gas dispersion around the building. This study investigated the turbulence and pollutant statistics around a high-rise building with large-eddy simulations and determined the influence of overhangs on the local wind flow and dispersion. Large-scale periodic vortex motion was detected. The results indicated that both the oncoming flow and the flow around the building followed a standard Gaussian distribution, whereas the occurrence frequencies of pollutant concentrations were far from Gaussian for pollutants discharged from both the rooftop and the ground behind the building. Near the pollutant sources, the positive concentration fluctuations occurred more frequently; occasionally, positive and negative fluctuations occurred equally. For the majority of areas far from the source, negative fluctuations were more common, but the maximum positive fluctuations were much larger. Overhangs changed the local flow structures near the building facade. Both the maximum concentration fluctuation and the maximum occurrence frequency decreased in the region between overhangs because turbulence was restricted.

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Effects of envelope features on wind flow and pollutant exposure in street canyons

Cited by 29 publications

References 35 publications

The effects of lateral entrainment on pollutant dispersion inside a street canyon and the corresponding optimal urban design strategies

The effects of lateral entrainment on pollutant dispersion inside a street canyon and the corresponding optimal urban design strategies

Evaluation on ventilation and traffic pollutant dispersion in asymmetric street canyons with void decks

Turbulence and Pollutant Statistics around a High-Rise Building with and without Overhangs

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