A parametric study of urban ventilation corridors for improving air quality in compact cities

Urban ventilation corridors are essential for improving air quality in compact city areas. Previous studies primarily focused on identifying the corridors in specific areas, with few investigations aimed at optimizing the ventilation efficiency of these corridors due to difficulties of clarifying the effects of each key parameter in complex urban environments. To address this challenge, a general compact urban model, consisting of one main corridor and two lateral-side canyons, is assumed as the computational domain. The impacts of the two main parameters (canyon widths and internal width variations of the corridors) on the urban ventilation are evaluated using numerical simulations. Results show that for uniform-width corridors, the polluted air from the lateral canyons is transported into the corridor. While this process helps reduce air pollution in the canyons, it weakens air movement in the corridor, leading to an increased air age of the corridor. When the canyons are of equal width to the corridor, the worst air condition occurs, with a 25% increase in air age for the corridor and a 97% for the whole urban compared to the canyon-free case. This poor air quality is maintained at small prevailing wind directions θ ≤ 15 o , but greatly improves for θ ≥ 22.5 o with a 32%–40% decrease in air age across the city. Moreover, the results show that when the corridor upstream section is wider than its downstream, the air quality can also be improved for the corridor itself and the overall city. • Effects of lateral canyons and internal width variations of ventilation corridor on air quality are evaluated. • Lateral-side canyons flanking the corridor weaken the ventilation capacity in the corridor. • Worst overall urban air quality appears when the lateral canyon is of equal width to the main corridor. • Inflow of polluted air from the canyons into the corridor is reduced for cases with wider corridor upstream. • Larger width ratio of the corridor upstream can effectively improve the urban air quality.