Experimental study of wind-induced ventilation in urban building of cube arrays with various layouts

Urban airflow and dispersion processes have become matters of great concern from the viewpoints of urban heat island phenomena, thermal comfort of pedestrians, hazard control for toxic gases, wind-induced ventilation of urban buildings, and so on. In this study, the authors measured the spatial distribution of the pressure drag acting on the walls of rectangular block arrays in a wind tunnel. The arrays were arranged with staggered, square, and diamond layouts under different conditions of roughness and packing density. The total drag and wind profiles of the arrays were preliminarily measured. On the basis of experimental results, the contribution of pressure drag to the total surface drag on staggered cube arrays was estimated at greater than 95%. In addition, the bulk pressure coefficients C_p for the arrays defined by mean velocity at a height of H, 2H and 20H were derived (H refers to the height of a block), and the clear relation between C_p and the block packing densities were shown for rough estimation of wind-induced ventilation in urban buildings. In addition, the authors present a simple mathematical expression to explain the relationship.