Abstract
Airflow behavior and indoor/outdoor PM2.5 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 PM2.5 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 PM2.5 compared with upper floors, and lower indoor PM2.5 values were found close to the tree canopy; (4) Wind pressure differences across each flat showed a poor correlation (R2 = 0.059), with indoor PM2.5 concentrations; and (5) Patterns with the long facade of buildings and trees perpendicular to the prevailing wind have the lowest indoor PM2.5 concentrations.
Highlights
With the rapid development of urbanization, particulate matter (PM) pollution, especially types with an aerodynamic diameter of less than 2.5 μm (PM2.5 ), has led to a dramatic decline in urban air quality
The results of this study suggest that wind pressure difference has little effect on difference indoor PM2.5 concentrations with the wind directions of 360° and 270°
PM2.5 due to partly wind-driven natural ventilation were studied by the standard k-ε model and the revised generalized drift flux model
Summary
With the rapid development of urbanization, particulate matter (PM) pollution, especially types with an aerodynamic diameter of less than 2.5 μm (PM2.5 ), has led to a dramatic decline in urban air quality. Outdoor-generated particles are major contributors to indoor pollution, without strong internal pollution sources [3,4,5,6]. Since most people spend approximately 85–90% of their time indoors, determining the relationships between outdoor particle sources and the corresponding indoor concentrations are especially significant when measuring particulate concentrations in occupied residences [7]. Natural ventilation is extensively used to provide better indoor air quality without using electricity [8]. In addition to the types of natural vents, the outdoor
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