Influence of Urban Road Green Belts on Pedestrian-Level Wind in Height-Asymmetric Street Canyons

Zeng, Fanlin; Simeja, David; Ren, Xinyi; Chen, Zhonggou; Zhao, Hanyi

doi:10.3390/atmos13081285

Cited by 4 publications

(2 citation statements)

References 21 publications

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“…By 2018, this proportion had surged to 55%. Projections indicate that this trend of urbanization will continue, with urban populations reaching an estimated 66% of the global population by the year 2050 [1]. China has notably exemplified this trend, undergoing a transformative surge in urbanization from 17.92% in 1978 to 52.27% in 2012, primarily attributed to the transformative policies of Reform and Opening [2].…”

Section: Introductionmentioning

confidence: 99%

Influence of Building Height Variation on Air Pollution Dispersion in Different Wind Directions: A Numerical Simulation Study

Pan,

2024

Applied Sciences

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Due to the rapid advancement of urbanization, traffic–related pollutants in street canyons have emerged as the primary source of PM2.5, adversely impacting residents’ health. Therefore, it is necessary to reduce PM2.5 concentrations. In this study, a three–dimensional steady–state simulation was conducted using Computational Fluid Dynamics (CFD). Three representative wind directions (θ = 0°, 45°, and 90°, corresponding to parallel, oblique, and perpendicular winds) and five different building height ratios (BHR = 0.25, 0.5, 1, 2, and 4) were used to explore the effect of building height variations on PM2.5 dispersion within street canyons. The results indicated that wind direction significantly influenced PM2.5 dispersion (p < 0.001). As θ increased (θ = 0°, 45°, and 90°), PM2.5 concentration in the canyon increased, reaching the most severe pollution under perpendicular wind. Building height variations had a minor impact compared to wind direction, but differences in PM2.5 concentration were still observed among various BHRs. Specifically, under parallel wind, the influence of BHR on PM2.5 dispersion was relatively small as compared to oblique and perpendicular winds. For oblique wind, PM2.5 concentrations varied based on BHR. Street canyons composed of low–rise or multi–story buildings (BHR = 0.25 or 4) slightly increased PM2.5 concentrations within the canyon, while the lowest PM2.5 concentration was observed at a BHR of 0.5. Under perpendicular wind, symmetrical (BHR = 1) and step–down canyons (BHR = 2 and 4) exhibited comparable peak concentrations of PM2.5, whereas step–up canyons (BHR = 0.25 and 0.5) showed relatively lower concentrations.

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Section: Introductionmentioning

confidence: 99%

Influence of Building Height Variation on Air Pollution Dispersion in Different Wind Directions: A Numerical Simulation Study

Pan,

2024

Applied Sciences

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“…It has been demonstrated that vegetation, especially trees in urban areas, has a favorable effect on the local wind environment [8,9]. On the one hand, trees reduce the wind speed behind them in urban areas by hindering the high-speed flow of incoming wind [10], changing the fluidity of the adjacent areas near the ground [11] and improving the comfort and health of the wind environment.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Wind-Induced Response in Urban Trees on the Surrounding Flow Field

Ren¹,

Zhang²,

Chen³

et al. 2023

Atmosphere

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In recent years, cities have experienced frequent climate changes and deteriorating wind environments. Urban vegetation has become an important measure to improve local microclimates with its flexible configuration. Leaves and branches also reorient with the direction of wind, affecting the airflow through the tree. However, trees are usually considered as stationary porous media areas and are not influenced by wind speed in existing numerical simulation studies. Therefore, by considering the response of a tree under natural wind, this study established a fitted relationship between porosity and wind speed by measuring the porosity of trees at different wind speeds in the field. A numerical model of the wind response of the tree was developed, and the tree drag coefficient was changed using the additional source term method to verify the feasibility of the model by measuring the wind environment behind the tree. To understand the effect of the wind-induced response on the surrounding flow field and its variation pattern, the surrounding flow fields of stationary tree (T-S) and wind-induced tree (T-D) at different wind speeds were compared and analyzed. The effect of porosity and height-to-width ratio under the wind-induced response of trees on the wind environment were quantified. It was found that at different wind speeds, as the wind speed increases, the tree porosity gradually increases and the drag coefficient decreases accordingly. The effective shading distance after wind response was 2.4H, which was 0.3H less compared to vertically fixed trees. The minimum wind speed increased linearly with plant porosity, and the minimum wind speed occurrence location and wind speed recovery distance were linearly and negatively correlated with tree height-to-width ratio. Therefore, the flow field around the tree was simulated to provide references for guiding tree planting and mitigating urban wind environments.

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Model Research on the Impact of Tree Greening Layout with Wind-responsive Characteristics on the Wind Environment in Residential Areas

Zhai,

Li,

Zhao

et al. 2024

Preprint

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With the concept of living environment put forward, creating a comfortable, healthy and energy-saving living environment has attracted more attention. The optimization of wind environment is of positive significance for urban ecological livability and alleviating urban heat island effect. Considering the wind-induced response of trees, this paper uses computer simulation technology to explore the distribution of flow field around greening in different building spaces and layout forms, and puts forward the optimization strategy of greening layout around buildings. The research shows that different building environments will also have a certain impact on the wind environment behind trees. Roof greening is more complicated than the wind field around buildings, and the wind-induced deformation of trees is obvious, and the wind reduction rate is higher. In addition, considering the influence of wind-induced response on trees, different planting spacing has different wind reduction efficiency. The proportion of ideal wind speed area in different horizontal layout forms of trees from large to small is row, enclosure and row.

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Influence of Urban Road Green Belts on Pedestrian-Level Wind in Height-Asymmetric Street Canyons

Cited by 4 publications

References 21 publications

Influence of Building Height Variation on Air Pollution Dispersion in Different Wind Directions: A Numerical Simulation Study

Influence of Building Height Variation on Air Pollution Dispersion in Different Wind Directions: A Numerical Simulation Study

The Influence of Wind-Induced Response in Urban Trees on the Surrounding Flow Field

Model Research on the Impact of Tree Greening Layout with Wind-responsive Characteristics on the Wind Environment in Residential Areas

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