The Spanwise Variation Of Roof-Level Turbulence In A Street Canyon Flow

The effect of upstream roughness on turbulent street canyon flow is presented. Horizontal measurements were conducted at near roof level of a street canyon using particle image velocimetry in a wind tunnel. Three upstream roughness arrays and two canyon width to height aspect ratios (W / h = 1 and 3) were investigated. The arrays consisted of 3D cubes (plan area density, lp = 25%), 1h spaced 2D bars skimming flow, lp = 50%) and 3h spaced 2D bars (wake interference flow, lp = 25%). Two-point correlations and integral length scales are computed over the different configurations. The results show a significant effect of upstream roughness on these quantities. It was found that a 3D upstream roughness has a significantly weaker correlation in the spanwise direction. A similar trend is observed in spanwise integral length scales. The shear layer boundary was found to be related to the strength of the correlations near roof level of the street canyon.