This paper concerns urban canopies populated with tall slender buildings. To clarify the controlling factors of urban canopies, we simulated a series of single high-rise buildings under fully developed turbulence at a realistic scale by large-eddy simulation. We then analysed correlations between the drag force and recirculation area, frontal area, surface area, floor area, porosity and inlet velocity. Our results show that the recirculation length and recirculation area were proportional to the width, height and wind speed, but were inversely proportional to the length of a building. New equations for the recirculation length and area are presented. The maximum error of the recirculation length equation was 6.66%, and the maximum error of the recirculation area equation was 7.49%. The drag source characteristic length was found to be proportional to the recirculation area, frontal area and surface area and inversely proportional to the porosity and height, but was not closely related to floor area. A new local scale drag source model was developed and applied to a complex urban canopy of Xi’an. The model was applied to 7 × 7 buildings and show good agreement with the solid wall simulation results.
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