LES Analysis on Advective and Diffusive Momentum Transports and Dominant Factor determing Total Drag of Densely Arranged Building Blocks

Abstract

This study aims to clarify a relationship between drag force of buildings and urban air ventilation at pedestrian level. At the first step of the study, LES was applied to the flow fields within high dense cities with buildings of various heights, and distributions of pressures acting on building surfaces and wall shear stress were examined in details. Contributions of the pressure difference and the wall shear stress to the total drag force caused by a group of buildings were compared. It was confirmed that the pressure differences between windward and leeward surface on upper parts of high-rise buildings largely contribute to the total drag force. On the other hand, the momentum transport to the downward direction in front of the windward faces of the high-rise buildings is very large compared to those in other regions.