Aerodynamic effect of overhang on a turbulent flow field within a two-dimensional street canyon

This paper reports the results of flow field analysis within and above a two-dimensional street canyon with various overhang lengths using large-eddy simulation (LES). Simulations were conducted for a constant canyon aspect ratio of W/H = 3, where W is the street width and H is the building height. Three different overhang lengths were simulated with P = 0H, 0.5H, and 1H in order to derive the mean and instantaneous flow characteristics. The results are compared with wind tunnel experiments for validation. The LES results of the mean flow with the P = 0H condition agree fairly well with the wind tunnel data. However, profiles of the standard deviation for the streamwise and vertical velocity components show large discrepancies at all measured locations. In addition, an increase in overhang length on both building facades significantly modifies the in-canyon flow pattern by limiting the penetration of the bulk flow into the canyon layer.