Influence of Various Urban Morphological Parameters on Urban Canopy Ventilation: A Parametric Numerical Study

Numerical simulation is vital for evaluating urban ventilation. However, accurate urban-scale ventilation modeling requires extensive building surface simulation for computational demand. The distributed drag force approach simplifies the urban canopy by modeling buildings as a porous volume that accounts for momentum and turbulence. This method is a practical solution for simulating urban airflow. The drag force coefficient (C-d) is a crucial aerodynamic parameter in this approach. This study examines how C-d varies with urban design parameters such as plan area density (lambda(p)), average building height (H), frontal area density (lambda(f)), floor aspect ratio (AR), and sky view factor (SVF). Employing extensive numerical simulations conducted under neutral atmospheric conditions, we explore ranges of lambda(p) = 0.04-0.07 and lambda(f) = 0.1-1.2. The numerical model has been validated against existing wind tunnel data. The results show that C-d is insensitive to the model scale and background wind speed. We discover a nonlinear relationship between C-d and the parameters lambda(p), lambda(f), and SVF. For urban layouts with cubic-shaped buildings, Cd peaks at different lambda(p) within the range of 0.2 similar to 0.8. When lambda(p) and H are constant, C-d has a linear relationship with AR and lambda(f). It is recommended to use lambda p, SVF, and AR as predictors for C-d across various urban configurations.