A parametric study of the effect of building layout on wind flow over an urban area

Exploration of the morphological characteristics of buildings in an urban area promotes an understanding of the complex interaction between the layout of building and the wind that flows over them. Based on an interdisciplinary study of building layout, a parameterization of layouts is presented. The wind network index (R_w) exhibits a high performance in distinguishing the effect of layout on aerodynamic characteristics. The physical interpretation of a smaller R_w indicates a higher accessibility of wind passages in the building area. Five types of layouts are presented based on identical planar area density, frontal area density, and cuboid roughness. Wind tunnel experiments evaluate the performance of R_w by measuring spatial average velocity, surface pressure on individual buildings, and total drag force. Results indicate that building layout has a significant influence on the spatial average velocity of wind near the buildings. Distributions of the local drag coefficient from pressure measurements illustrate a relatively flat trend at downstream area in cases of high R_w with insufficient ventilation. Maximum values for overall drag, downstream fluctuation, and velocity attenuation are apparent in the diagonal-grid case. Moreover, a negative correlation is indicated obviously between the overall drag versus layout and the spatial-average velocity versus layout. Results of the drag variation as a function of layout show a similar trend as the drag effect change with the planar area density. Therefore, this study may help to elucidate the effects of building layout on the drag effect and to improve the numerical precision of urban canopy models.