Impacts of specific street geometry on airflow and traffic pollutant dispersion inside a street canyon

Huang, Yuandong; Ren, Su-qi; Xu, Nuo; Luo, Yang; Sin, Chung Hyok; Cui, Peng-Yi

doi:10.1007/s11869-021-01101-y

Cited by 13 publications

(15 citation statements)

References 38 publications

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“…The governing equation for assessing the gas pollutant transport is defined by Eq. ( 1 ) (Huang et al 2022 ): where C is the time-averaged pollutant concentration, and D m and D t ( D t = v t /Sc t ) are respectively the molecular and turbulent diffusivity. Sc t is the turbulent Schmidt number and S is the pollutant source term.…”

Section: Methodsmentioning

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 ).…”

Section: Introductionmentioning

confidence: 99%

“…The results showed that void decks can dramatically improve wind comfort around the buildings, and the effect varies greatly depending on the wind direction (0°, 90°, 180°) and building shape. Huang et al ( 2022 ) carried out a 2D numerical simulation for symmetric street canyons and revealed that void decks have significant effects on the airflow structure and pollutant diffusion inside the street canyon. Comparing with the regular street canyon with a main clockwise vortex, the void deck can cause several vortices when a strong stream of air passes through the canyon.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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show abstract

“…Differences in spatial patterns of the streets and their design speed also influence their vitality [ 32 ]. Evidence also shows that street spatial patterns have implications for urban microclimate and pollution, most of which are SVI-based analyses [ 33 , 34 , 35 ]. In general, SVI is an important source of data for street space studies [ 36 ], and the mutual relations of street spatial patterns and vitality are supported by a wide range of studies.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Relationship between Urban Street Spatial Patterns and Street Vitality: A Case Study of Guiyang, China

Yang

et al. 2023

IJERPH

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Understanding how street spatial patterns are related to street vitality is conducive to enhancing effective urban and street design. Such analysis is facilitated by big data technology as it enables more accurate methods. This study cites data from street view imagery (SVI) and points of interest (POI) to assess street vitality strength after the classification of street spatial and vitality types to explore the relationship between street spatial patterns and street vitality with a further discussion on the layout features of street vitality and its strength in various street spatial patterns. First, street spatial patterns are quantified based on SVI, which are further classified using principal component analysis and cluster analysis; POI data are then introduced to identify street vitality patterns and layout, and the strength of street vitality is evaluated using spatial overlay analysis. Finally, relevance analysis is explored to cast light on the relationship between street vitality layout and street spatial patterns by overlaying street spatial pattern, street vitality types, and street vitality strength in the grid cells. This paper takes the urban area of Guiyang, China, as an example and the analysis shows that a pattern is discovered in Guiyang regarding the layout of street vitality types and vitality strengths across different street spatial patterns; compact street spaces should be prioritized in designing street space renovation; and cultural leisure vitality is most adaptive to street spatial patterns. Based on big data and using grids to understand the intrinsic relationship between street spatial patterns and the type and strength of street vitality, this paper brings more options to urban street studies in terms of perspective and methodology.

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“…In addition, the street canyon structure (symmetric or asymmetric structure (Reiminger et al 2020), VD (Huang et al 2020), viaduct (Hao et al 2019), building roof (Zhang et al 2021)) also significantly affects the airflow and pollutant dispersion inside the canyon. 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)).…”

Section: Introductionmentioning

confidence: 99%

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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Impacts of specific street geometry on airflow and traffic pollutant dispersion inside a street canyon

Cited by 13 publications

References 38 publications

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

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

Exploring the Relationship between Urban Street Spatial Patterns and Street Vitality: A Case Study of Guiyang, China

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

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