Effect of protruding eave on the turbulence structures over two-dimensional semi-open street canyon

Abstract

The semi-open configuration of canyons is often associated with elevated structures such as eaves, awnings, balconies and arcades. Although numerous researchers have investigated the influence of these structures on canyon ventilation, detail investigations on the flow fields over two-dimensional (2D) semi-open street canyon with protruding eaves at the building level have not been studied adequately. Therefore, in this study, a series of large eddy simulation (LES) was performed to investigate the effect of various eave designs on the modification of flow structure and turbulent characteristics within and above 2D semi-open street canyon. The size of the vortices changes significantly with increasing length of the eaves as well as with the positioning of the eaves on the windward or leeward side or on both building facades, as the detachment and impingement points of the flow change. Spatial distribution of the turbulence statistics depicts a strong dependency on the eave dimension and position. The turbulence intensities and Reynolds stress were systemically reduced as the presence of eaves attenuate the penetration of the above flow into the street canyon. However, spatially-averaged profiles showed a clear dependence of turbulence statistics on the total length of eaves instead of the position of individual eave. The spatio-temporal of the mean wind speed showed an S-shaped profile in all cases instead of the different eave configurations. Furthermore, the occurrence frequency of ejections was dominant within the canyon, while above the building height sweeps was greater.