Effects of roadside morphologies and moving vehicles on street canyon ventilation

The influence of roadside morphology and the movement of vehicles on street canyon ventilation is important, but their coupling effect is still unclear. This study aimed to determine the best structural design for roadside buildings while considering moving vehicles’ effect on ventilation. The morphologies examined were podium, cantilever, rain shed, balcony, outdoor air-conditioning unit, and reference structures. The ventilation capacity of partial areas and the entire lane in the sidewalk and cycle lane was analyzed based on the age of air and net escape velocity (NEV). When a vehicle moves through a street canyon, the ventilation capacity of the zone part at the rear of the vehicle is improved, especially for the cycle lane on the windward side. However, for the entire lane, moving vehicles reduce the ventilation capacity by about 0.2–1.4%, with an average reduction of 0.8%. Therefore, when a vehicle passed through the street canyon, it reduced the ventilation capacity of an entire lane under a perpendicular wind direction. The cantilever morphology exhibited the best ventilation based on the vortex distribution and ventilation indices analysis. Its NEV values were 5% higher than that of the reference.