Effect of building parameters on urban ventilation efficiency for pedestrian areas: Considering internal and external pollution sources

This study investigated the impact of contemporary residential building layouts on urban ventilation efficiency through computational fluid dynamics simulations. Using a representative Shanghai residential district as a baseline model, multiple urban configurations were developed by systematically varying key parameters including building coverage ratio (BCR), passage width, building height distribution, and spatial arrangement while maintaining a constant floor area ratio. The analysis incorporated both internal and external pollution sources to assess pollutant dispersion patterns across different urban morphologies. Ventilation performance was evaluated using three dimensionless indices: spatially-averaged wind speed ratio, normalized concentration, and visitation frequency. Complementary analyses of air exchange rates and pollutant flux further elucidated ventilation mechanisms and interrelationships between evaluation indices. Main findings reveal that: enhanced ventilation correlates strongly with wider pedestrian passages and lower building coverage ratios; staggered building arrays demonstrate superior ventilation performance compared to aligned configurations under high-density conditions (BCR ≥0.166); vertical height variation in compact layouts (BCR = 0.33) improves ventilation efficiency by 8.8–22.1 % under perpendicular wind incidence (90°); compared to external pollution source, internal source show strong morphological sensitivity. This work validates the robustness of existing design parameter (passage ratio) in ventilation design and expands its scope of application for urban design and planning.