Numerical investigations of flow and passive pollutant exposure in high-rise deep street canyons with various street aspect ratios and viaduct settings

He, Lejian; Hang, Jian; Wang, Xuemei; Lin, Borong; Li, Xiaohui; Lan, Guangdong

doi:10.1016/j.scitotenv.2017.01.138

Cited by 129 publications

(72 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The road tunnel environment could be regarded as a special kind of indoor environment but on a much larger scale than an indoor room, it approximately fits the scale of urban street canyons. The standard k-ε model can well-simulate the airflow and pollutant dispersion with a performance which has been highly validated in urban scale studies [27]. Ghadiri [32] investigated the simulation performance of different numerical models in cases of two-sided rectangular wind catchers.…”

Section: Cfd Methodologymentioning

confidence: 99%

“…S is the pollutant emission rate. Here, D t = ν t /Sc t and Sc t is the turbulent Schmidt number whose value is set as Sc t = 0.7 following the literature [27,40,41].…”

Section: Cfd Setup In Pollutant Dispersion Modellingmentioning

confidence: 99%

“…In order to evaluate the impacts of different types of ventilation design on air pollutants within a tunnel environment, this research adopts the concept of the intake fraction (IF), which is defined as the fraction of the total emission inhaled by the population [27][28][29][30]. In this research, CFD methodology with a validation process is applied for investigation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study

et al. 2018

Self Cite

View full text Add to dashboard Cite

Providing efficient ventilation in road tunnels is essential to prevent severe air pollution exposure for both drivers and pedestrians in such enclosed spaces with heavy vehicle emissions. Longitudinal ventilation methods like commercial jet fans have been widely applied and confirmed to be effective for introducing external fresh air into road tunnels that are shorter than 3 km. However, operating tunnel jet fans is energy consuming. Therefore, for small-scale (~100 m–1 km) road tunnels, mechanical ventilation methods might be highly energetically expensive and unaffordable. Many studies have found that the use of wind catchers could improve buildings’ natural ventilation, but their effect on improving natural ventilation in small-scale road tunnels has, hitherto, rarely been studied. This paper, therefore, aims to quantify the influence of style and arrangement of one-sided flat-roof wind catchers on ventilation performance in a road tunnel. The concept of intake fraction (IF) is applied for ventilation and pollutant exposure assessment in the overall tunnel and for pedestrian regions. Computational fluid dynamics (CFD) methodology with a standard k-epsilon turbulence model is used to perform a three-dimensional (3D) turbulent flow simulation, and CFD results have been validated by wind-tunnel experiments for building cross ventilation. Results show that the introduction of wind catchers would significantly enhance wind speed at pedestrian level, but a negative velocity reduction effect and a near-catcher recirculation zone can also be found. A special downstream vortex extending along the downstream tunnel is found, helping remove the accumulated pollutants away from the low-level pedestrian sides. Both wind catcher style and arrangement would significantly influence the ventilation performance in the tunnel. Compared to long-catcher designs, short-catchers would be more effective for providing fresh air to pedestrian sides due to a weaker upstream velocity reduction effect and smaller near-catcher recirculation zone. In long-catcher cases, IF increases to 1.13 ppm when the wind catcher is positioned 240 m away from the tunnel entrance, which is almost twice that in short-catcher cases. For the effects of catcher arrangements, single, short-catcher, span-wise, shifting would not help dilute pollutants effectively. Generally, a design involving a double short-catcher in a parallel arrangement is the most recommended, with the smallest IF, i.e., 61% of that in the tunnel without wind catchers (0.36 ppm).

show abstract

Section: Cfd Methodologymentioning

confidence: 99%

“…S is the pollutant emission rate. Here, D t = ν t /Sc t and Sc t is the turbulent Schmidt number whose value is set as Sc t = 0.7 following the literature [27,40,41].…”

Section: Cfd Setup In Pollutant Dispersion Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…Combining the simulation method and the architectural design strategy, it enables architects to better design and evaluate the city wind environment. Studies on outdoor environment by CFD method mainly focus on airflow pattern analysis [16,17], human comfort evaluation at the pedestrian level around buildings [18], and the prediction of pollution dispersion [19]. Over the last few decades, many attempts have been made to link urban ventilation research with the urban design in a given condition.…”

Section: Study Casementioning

confidence: 99%

“…The ventilation has been found to have a close relationship with the building layout, which subsequently affects the air quality in street canyons [20]. Moreover, the canyon aspect ratio and the orientation of street canyons are two crucial parameters informing the urban microclimates and influencing the thermal comfort of pedestrians, which is more obvious in full-scale high-rise deep street canyons [19,21]. The vertical microclimate and mass-exchange have also been investigated in different street canyons with different geometries [22].…”

Section: Study Casementioning

confidence: 99%

Numerical Study on the Urban Ventilation in Regulating Microclimate and Pollutant Dispersion in Urban Street Canyon: A Case Study of Nanjing New Region, China

et al. 2017

View full text Add to dashboard Cite

Abstract:Urban ventilation plays an important role in regulating city climate and air quality. A numerical study was conducted to explore the ventilation effectiveness on the microclimate and pollutant removal in the urban street canyon based on the rebuilt Southern New Town region in Nanjing, China. The RNG k − ε turbulence model in the computational fluid dynamics (CFD) was employed to study the street canyon under parallel and perpendicular wind directions, respectively. Velocity inside of the street canyon and temperature on the building envelopes were obtained. A novel pressure coefficient was defined, and three methods were applied to evaluate the urban ventilation effectiveness. Results revealed that there was little comfort difference for the human body under two ventilation patterns in the street canyon. Air stagnation occurred easily in dense building clusters, especially under the perpendicular wind direction. In addition, large pressure coefficients (C P > 1) appeared at the windward region, contributing to promising ventilation. The air age was introduced to evaluate the "freshness" of the air in the street canyon and illustrated the ventilation effectiveness on the pollutant removal. It was found that the young air distributed where the corresponding ventilation was favorable and the wind speed was large. The results from this study can be useful in further city renovation for the street canyon construction and municipal planning.

show abstract

Exposure characteristics of ultrafine particles on urban streets and its impact on pedestrians

Qiu

2022

Environ Monit Assess

View full text Add to dashboard Cite

Numerical investigations of flow and passive pollutant exposure in high-rise deep street canyons with various street aspect ratios and viaduct settings

Cited by 129 publications

References 65 publications

Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study

Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study

Numerical Study on the Urban Ventilation in Regulating Microclimate and Pollutant Dispersion in Urban Street Canyon: A Case Study of Nanjing New Region, China

Exposure characteristics of ultrafine particles on urban streets and its impact on pedestrians

Contact Info

Product

Resources

About