Abstract—This study investigates how street-tree configurations and wind orientation jointly influence PM2.5 dispersion in dense urban canyons of tropical cities. Using three-dimensional Computational Fluid Dynamics (CFD) simulations based on the Reynolds-Averaged Navier-Stokes (RANS) model, the research examines nine vegetation scenarios under two prevailing monsoonal wind regimes, perpendicular (west) and parallel (south), along Sukhumvit Road, Samut Prakan Municipality, Thailand. Results reveal that PM2.5 mitigation effectiveness is critically dependent on the interaction between configuration and incident wind angle. All tree-scenarios significantly reduced average pedestrian-level (1.5 m) PM2.5 concentrations compared to the treeless baseline (S1). The single 6-meter leeward sidewalk tree configuration demonstrated the highest local PM2.5 reduction. Tree height exerts a directional aerodynamic control; 10-meter trees significantly enhanced streamwise velocity under parallel flow (up to a 26% increase), thereby improving ventilation, but restricted flow under perpendicular conditions, reducing wind speed by 58%. These findings confirm a dual role where all scenarios yield overall PM2.5 reductions, but localized accumulation risks exist due to suppressed ventilation. Optimal PM2.5 mitigation requires strategic design, specifically selecting sub-eave tree heights and maintaining adequate canopy clearance, to prioritize beneficial aerodynamic mixing and inform climate-responsive urban planning.
Keywords—street tree, PM2.5, Computational Fluid Dynamics (CFD), urban area
Cite: Wanarat Konisranukul, Amorntep Jirasakjamroonsri, and Kamolrat Smankasivit, "Evaluating Street Tree Performance in PM2.5 Mitigation under Different Wind Directions: Insights from a CFD Study," International Journal of Environmental Science and Development vol. 17, no. 3, pp. 281-291, 2026.
Copyright © 2026 by the authors. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).