Prediction of Wind Environment and Indoor/Outdoor Relationships for PM2.5 in Different Building–Tree Grouping Patterns

Abstract

Airflow behavior and indoor/outdoor PM 2.5 dispersion in different building-tree grouping patterns depend significantly on the building-tree layouts and orientation towards the prevailing wind. By using a standard k-ε model and a revised generalized drift flux model, this study evaluated airflow fields and indoor/outdoor relationships for PM 2.5 resulting from partly wind-induced natural ventilation in four hypothetical building-tree grouping patterns. Results showed that: (1) Patterns provide a variety of natural ventilation potential that relies on the wind influence, and buildings that deflect wind on the windward facade and separate airflow on the leeward facade have better ventilation potential; (2) Patterns where buildings and trees form a central space and a windward opening side towards the prevailing wind offer the best ventilation conditions; (3) Under the assumption that transported pollution sources are diluted through the inlet, the aerodynamics and deposition effects of trees cause the lower floors of a multi-storey building to be exposed to lower PM 2.5 compared with upper floors, and lower indoor PM 2.5 values were found close to the tree canopy; (4) Wind pressure differences across each flat showed a poor correlation (R 2 = 0.059), with indoor PM 2.5 concentrations; and (5) Patterns with the long facade of buildings and trees perpendicular to the prevailing wind have the lowest indoor PM 2.5 concentrations.

How Outdoor Trees Affect Indoor Particulate Matter Dispersion: CFD Simulations in a Naturally Ventilated Auditorium

“…When the air exchange frequency is constant, airflow discharges rapidly, removing pollutants and reducing indoor particulate matter. Previous studies have demonstrated that absolute or relative difference in wind pressure in buildings is weakly correlated with indoor particle concentrations [58,88]. Our simulation results indicate that the natural ventilation rate is significantly and positively correlated with indoor particle concentration linked to window opening size.…”

Are Green Walls Better Options than Green Roofs for Mitigating PM10 Pollution? CFD Simulations in Urban Street Canyons

“…All metrics obtained were within the allowable ranges, indicating the models could suitably reproduce the actual environment of street canyon (Table 1). Additionally, the present authors compared this model with a wind tunnel experiment from a previous study that also showed that this model could accurately represent the actual street canyon environment [41]. The model was built according to site dimensions.…”

“…To investigate the effects of GRs and GWs on PM 10 concentration distributions in different street canyon configurations, street canyon aspect ratios (H/W) were set to 0.5, 1.0, and 2.0. Since the dust-retaining ratio of the building envelope was low, it was treated as a solid block without consideration of dust retention and wind penetration [41]. Herbaceous plants are generally used for GWs with a height of 0.1-0.5 m [42].…”

Recent Advances in Urban Ventilation Assessment and Flow Modelling

“…Hong et al [10] present results obtained from CFD simulations to determine the effects of four typical building-tree grouping patterns on the outdoor wind environment and the indoor/outdoor relationships for PM 2.5 as a result of partly wind-induced natural ventilation in Beijing; the relationship between the resulting wind pressure differences and indoor PM 2.5 concentrations; and which building-tree grouping pattern could provide the best ventilation potential or provide the lowest indoor PM 2.5 concentrations. Results clearly indicate that airflow and indoor/outdoor PM 2.5 dispersion strongly depend on the relationships of building layouts, tree arrangements, and orientation towards the prevailing wind.…”