Drag distributions of non-uniform buildings from surface pressure measurements in wind tunnel

In an urban area, the dominated effect of buildings on wind environment is significantly influenced by the non-uniform buildings. In this work, the surface wind pressure and total drag force measurement on non-uniform buildings were performed, utilizing wind tunnel experiments with the aim to improve the understanding and evaluation accuracy about flow over buildings in the urban area. Buildings models were designed with four morphological parameters which are planar area density, frontal area density, building shape and buildings layout. Two pressure measurement schemes: measurements on multiple pressure modules roughly aligned and on three pressure modules roughly scattered in a line along the wind direction were compared to preliminarily explore the estimation method of total drag force from surface pressure measurements. The effect of reference velocity and non-uniform characteristics on the drag were also investigated. Experimental results indicate that the form drag dominates the total drag force of the non-uniform buildings in an urban area under fully developed turbulence. The critical friction Reynolds number (Re∗, based on 0.1H as roughness height) for keeping Reynolds number independent is around 650. Results also imply the measurement scheme on three pressure modules can depict the general drag distribution along the wind direction approximately; the shape and the volume of the most windward building determine the magnitude of its local drag force while the density and the layout determine the drag coefficient distribution of buildings.