Large eddy simulation study on pedestrian-level wind environments around elevated walkways and influential factors in ideal urban street canyons

Constructing elevated walkway systems is an effective and prevalent strategy for densely populated cities to improve pedestrian walkability and road safety. Nevertheless, adding an elevated walkway inside the street will inevitably influence the local wind environment, which has rarely been investigated. This study aims to examine the pedestrian-level wind environment around the elevated walkway in three-dimensional (3D) ideal urban street canyons using large eddy simulations. The impacts of street aspect ratio (H/W = 1, 2, 3), elevated walkway width (W_ew/W = 0.2, 0.4, 0.6), and sidewall type (open, semi-hermetic, hermetic) on the mean wind velocity and gust wind velocity fields were quantified. Results indicate that the elevated walkway has an adverse effect on the pedestrian-level wind environment. After adding an elevated walkway, the area-weighted average mean and gust wind velocities of the target street are decreased, with a maximum rate of over 20% and 30%. Increasing H/W may be positive or negative for the pedestrian-level wind environment, as the overall mean and gust wind velocities do not show monotonic variations with H/W. Extremely wide elevated walkways should be avoided as the pedestrian-level mean and gust wind environments worsen with increased walkway width. Using semi-hermetic or hermetic sidewalls slightly improves the pedestrian-level mean and gust wind environments. This study promotes the knowledge of the impacts of elevated walkways, street aspect ratio, and walkway designs on pedestrian-level mean and gust wind environments, providing a scientific basis for further research.