Effects of void deck on the airflow and pollutant dispersion in 3D street canyons

Sin, Chung Hyok; Luo, Yang; Jon, Kwang Song; Cui, Peng-Yi; Huang, Yuandong

doi:10.1007/s11356-022-21827-1

Cited by 6 publications

(22 citation statements)

References 52 publications

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“…2c). In addition, buildings with VD (height H/6, 3 m at the full scale) are modeled as ideal blocks with empty space below (Chew and Norford (2019); Huang et al (2021); Sin et al (2022)). For the three street canyons constructed above, which are constructed according to the VD location, the influence of seven wind directions are considered; therefore, twenty-one numerical cases are adopted in this study.…”

Section: Street Canyon Configurationsmentioning

confidence: 99%

“…In actual situation, buildings with VDs are lifted by pillars. However, previous studies have not considered the effects of pillars to simplify numerical simulations (Sin et al (2022); Chew and Norford (2019); Huang et al (2021); Chen and Mak (2021)). Since the pillars of the VD increase the airflow resistance, it is expected that the airflow velocity entering through the VD in the actual situation will be lower than the velocity in this study.…”

Section: Limitations and Future Workmentioning

confidence: 99%

“…Among them, VDs can provide very beneficial effects in removing traffic pollutants and ameliorating thermal discomfort within the street canyons by substantially changing the flow fields (Ma et al (2021); Huang et al (2021)). VD is an architectural structure widely used in urban design of tropical countries, which refers to the elevated ground floor under public apartments (Chew and Norford (2019); Sin et al (2022)). Unlike temperate regions, the seasonal division is not obvious in the tropical zone.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of the ventilation and pollutant exposure risk level inside 3D street canyon with void deck under different wind directions

Sin

Jon

et al. 2022

Preprint

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With continuous global warming, growing urban population density and increasing compactness of urban buildings, VD (void deck) street design has become increasingly popular in city planning, especially in tropical countries. However, understanding on traffic pollutant dispersion in the VD street canyons is still at early stage. This paper quantitatively evaluates the effects of VD location and wind direction on the ventilation and traffic pollutant exposure inside the street canyon with VDs. The results show that the VD location and wind direction have significant effects on the flow field and pollutant dispersion inside the canyon. When VDs are located at the upwind building, downwind building, and both buildings, the wind directions with maximum ACH (air exchange rate) are 60°, 30° and 60°, respectively. Under seven wind directions (0°, 15°, 30°, 45°, 60°, 75°, and 90°), the VD provides higher ACH than that of the regular canyon, especially at high α (angle between the approaching wind and the canyon axis). When α = 90°, regular canyon has the lowest ventilation capacity, but ACH values of canyons with both VDs or the leeward VD are 189.1% and 177.6% of regular canyon, respectively. Also, mean K (dimensionless pollutant concentration) values of the canyon wall and pedestrian respiration plane on one side where VD is located are significantly reduced compared to the regular canyon. Therefore, when VDs are at both buildings, both pedestrian respiration planes and walls have the lowest K values, thus providing the best living environment for pedestrians and near-road residents. As α increases, the K values on both respiration planes significantly decrease except for the leeward respiration plane of the canyon with the windward VD. These findings can help to design urban street canyons for mitigating traffic pollution risk and improving ventilation in tropical cities with frequently changing wind directions.

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Section: Street Canyon Configurationsmentioning

confidence: 99%

Section: Limitations and Future Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of the ventilation and pollutant exposure risk level inside 3D street canyon with void deck under different wind directions

Sin

Jon

et al. 2022

Preprint

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“…However, the rapid increase in urban population density and consequent urban development cause various problems (Du et al 2017 ; Ng 2009 ). In order to build more buildings in a limited space, modern urban design is developing toward densification-high-rise (Sin et al 2022 ; Chen and Mak 2021a ). Such a dense urban structure suppresses fresh air circulation and produces a considerable negative impact on citizens (Ming et al 2021 ; López-Pérez et al 2019 ).…”

Section: Introductionmentioning

confidence: 99%

“…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 ). Some studies investigating the effects of street geometric properties (street width ratio and building height ratio) (Xie et al 2006 ; Reiminger et al 2020 ), street trees (Shen et al 2022 ; Sun and Zhang 2018 ), viaduct (Hao et al 2019 ), and solar radiation (Li et al 2020 ) on traffic pollution dispersion conclude that street geometric structures have a significant influence on the airflow and pollutant distribution pattern inside the street canyon.…”

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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Evaluation of the ventilation and pollutant exposure risk level inside 3D street canyon with void deck under different wind directions

Sin¹,

Jon²,

Un³

et al. 2023

Environ Sci Pollut Res

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With continuous global warming, growing urban population density and increasing compactness of urban buildings, VD (void deck) street design has become increasingly popular in city planning, especially in tropical countries. However, understanding on traffic pollutant dispersion in the VD street canyons is still at early stage. This paper quantitatively evaluates the effects of VD location and wind direction on the ventilation and traffic pollutant exposure inside the street canyon with VDs.The results show that the VD location and wind direction have significant effects on the flow field and pollutant dispersion inside the canyon. When VDs are located at the upwind building, downwind building, and both buildings, the wind directions with maximum ACH (air exchange rate) are 60°, 30° and 60°, respectively. Under seven wind directions (0°, 15°, 30°, 45°, 60°, 75°, and 90°), the VD provides higher ACH than that of the regular canyon, especially at high α (angle between the approaching wind and the canyon axis). When α = 90°, regular canyon has the lowest ventilation capacity, but ACH values of canyons with both VDs or the leeward VD are 189.1% and 177.6% of regular canyon, respectively. Also, mean K (dimensionless pollutant concentration) values of the canyon wall and pedestrian respiration plane on one side where VD is located are significantly reduced compared to the regular canyon. Therefore, when VDs are at both buildings, both pedestrian respiration planes and walls have the lowest K values, thus providing the best living environment for pedestrians and near-road residents. As α increases, the K values on both respiration planes significantly decrease except for the leeward respiration plane of the canyon with the windward VD.These findings can help to design urban street canyons for mitigating traffic pollution risk and improving ventilation in tropical cities with frequently changing wind directions.

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Effects of void deck on the airflow and pollutant dispersion in 3D street canyons

Cited by 6 publications

References 52 publications

Evaluation of the ventilation and pollutant exposure risk level inside 3D street canyon with void deck under different wind directions

Evaluation of the ventilation and pollutant exposure risk level inside 3D street canyon with void deck under different wind directions

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

Evaluation of the ventilation and pollutant exposure risk level inside 3D street canyon with void deck under different wind directions

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