A numerical study on urban-like block arrays’ drag force and its correlation with ventilation efficiency

Abstract

Abstract This work conducted Computational Fluid Dynamics (CFD) simulations to investigate the drag force (F) and its relation to ventilation of four groups of urban-like block arrays with planar area index (λP ) ranging from 0.0625 to 0.56. Simulations were performed employing the standard k-ε turbulence model after conducting a grid sensitivity test and validating the computational settings against wind tunnel data. The results showed that cases with larger λp , slab-shaped buildings, and staggered layout have higher values of F. As for the subcases within each group, F shows a significant increase for 0.0625 < λp < 0.25, and then only a slight increase for 0.25 < λp < 0.56; while the drag coefficient (Cd ) shows a linear increase along with λp . The further linear regression analysis showed that the spatially averaged velocity and air change rate are strongly negatively correlated with F, which supports the effectiveness of F in reflecting ventilation efficiency, particularly for evaluating urban block-scale ventilation.