Turbulent flow and dispersion inside and around elevated walkways

Duan, G.; Brimblecombe, Peter; Chu, Y.L.; Ngan, K.

doi:10.1016/j.buildenv.2020.106711

Cited by 15 publications

(6 citation statements)

References 55 publications

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“…15(c)). Duan et al [215] observed that the mean flow decelerated below elevated walkways and increased the concentration by up to 20%, although the level of TKE around the elevated walkways was improved.…”

Section: Effects Of Viaductsmentioning

confidence: 99%

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Review on pollutant dispersion in urban areas-part A: Effects of mechanical factors and urban morphology

Ming

Liu

et al. 2021

Building and Environment

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Section: Effects Of Viaductsmentioning

confidence: 99%

“…The viaduct, which had a fixed height, resulted in a nearly three-fold increase in the volumetric <P_IF> in a deep canyon (H/W =5) but only slightly influenced the <P_IF> in a relatively low canyon (H/W =1 and 3) [215] a, b CFD (V)…”

Section: Effects Of Viaductsmentioning

confidence: 99%

Review on pollutant dispersion in urban areas-part A: Effects of mechanical factors and urban morphology

Ming

Liu

et al. 2021

Building and Environment

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“…Thanks to the continuous advances in computational power, this review shows that 17.2% of the studies have applied the LES approach to the studies of the PLW flow fields in different urban settings in the recent five years. There are studies focusing on simplified geometries of isolated buildings (Liu, Yu, et al, 2020;Tse et al, 2020;Zhang, Ooka, & Kikumoto, 2020), generic urban settings of building arrays (Freidooni et al, 2021;Ikegaya et al, 2017;Ishida et al, 2018;, street canyons (Duan et al, 2020;Puigferrat et al, 2021;Salim et al, 2020), and complex urban areas (Adamek et al, 2017;Antoniou et al, 2017;Zhang, Kwok, et al, 2021). In some earlier studies, researchers considered different aspects of reality in their simulations.…”

Section: Scale Resolving Simulationsmentioning

confidence: 99%

“…The realistic elements are also observed in the studies investigated. They include roof types (Liu, Yu, et al, 2020), parked cars (Gallagher & Lago, 2019), elevated walkways (Duan et al, 2020), tree crowns (Matsuda et al, 2018), building balconies (Zheng et al, 2022), and terraced houses (Salim et al, 2020). These realistic elements either connect to design features or human activities that are common in the current urban environment.…”

Section: Scale Resolving Simulationsmentioning

confidence: 99%

Recent advances in modeling turbulent wind flow at pedestrian-level in the built environment

Zhong

Liu

Zhao

et al. 2022

ARIN

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Pressing problems in urban ventilation and thermal comfort affecting pedestrians related to current urban development and densification are increasingly dealt with from the perspective of climate change adaptation strategies. In recent research efforts, the prime objective is to accurately assess pedestrian-level wind (PLW) environments by using different simulation approaches that have reasonable computational time. This review aims to provide insights into the most recent PLW studies that use both established and data-driven simulation approaches during the last 5 years, covering 215 articles using computational fluid dynamics (CFD) and typical data-driven models. We observe that steady-state Reynolds-averaged Navier-Stokes (SRANS) simulations are still the most dominantly used approach. Due to the model uncertainty embedded in the SRANS approach, a sensitivity test is recommended as a remedial measure for using SRANS. Another noted thriving trend is conducting unsteady-state simulations using high-efficiency methods. Specifically, both the massively parallelized large-eddy simulation (LES) and hybrid LES-RANS offer high computational efficiency and accuracy. While data-driven models are in general believed to be more computationally efficient in predicting PLW dynamics, they in fact still call for substantial computational resources and efforts if the time for development, training and validation of a data-driven model is taken into account. The synthesized understanding of these modeling approaches is expected to facilitate the choosing of proper simulation approaches for PLW environment studies, to ultimately serving urban planning and building designs with respect to pedestrian comfort and urban ventilation assessment.

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“…At the base of the canyon, the wind speeds can be low, even if the traffic-generated turbulence is strong. Architectural features, such as advertising signage, overhead walkways [3] and a range of street features [4] such as bus shelters [5] and roadside vegetation [6][7][8], inhibit the airflows. The ventilation within the canyon may be suppressed [9], and vortices can leave dead zones with stagnant air [2].…”

Section: Introductionmentioning

confidence: 99%

NOx and CO Fluctuations in a Busy Street Canyon

2021

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Busy street canyons can have a large flow of vehicles and reduced air exchange and wind speeds at street level, exposing pedestrians to high pollutant concentrations. The airflow tended to move with vehicles along the canyon and the 1-s concentrations of NO, NO2 and CO were highly skewed close to the road and more normally distributed at sensors some metres above the road. The pollutants were more autocorrelated at these elevated sensors, suggesting a less variable concentration away from traffic in the areas of low turbulence. The kerbside concentrations also showed cyclic changes approximating nearby traffic signal timing. The cross-correlation between the concentration measurements suggested that the variation moved at vehicle speed along the canyon, but slower vertically. The concentrations of NOx and CO were slightly higher at wind speeds of under a metre per second. The local ozone concentrations had little effect on the proportion of NOx present as NO2. Pedestrians on the roadside would be unlikely to exceed the USEPA hourly guideline value for NO2 of 100 ppb. Across the campaign period, 100 individual minutes exceeded the guidelines, though the effect of short-term, high-concentration exposures is not well understood. Tram stops at the carriageway divider are places where longer exposures to higher levels of traffic-associated pollutants are possible.

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Turbulent flow and dispersion inside and around elevated walkways

Cited by 15 publications

References 55 publications

Review on pollutant dispersion in urban areas-part A: Effects of mechanical factors and urban morphology

Review on pollutant dispersion in urban areas-part A: Effects of mechanical factors and urban morphology

Recent advances in modeling turbulent wind flow at pedestrian-level in the built environment

NOx and CO Fluctuations in a Busy Street Canyon

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