Structure of turbulence within an urban street canyon

Details associated with the structure of turbulence in an urban street canyon are presented using data from a field experiment conducted in downtown Oklahoma City during the month of July 2003 (Joint Urban 2003). An attempt is made to address the lack of understanding associated with the interaction between the various urban flow regimes. In particular, attention is focused on the interaction between flow deep within the roughness elements of a real city and the overlying sub layers. Observations from Oklahoma City field data indicate the existence of various flow regimes in the street canyon that depend upon (amongst other parameters) the mean upstream incident wind angle. Mean velocities, variances and turbulent fluxes within the street canyon for different upwind conditions are quantified and presented. It was generally found that in the canyon, wind velocities are characterized by high variances (in all three components) with magnitudes significantly greater than the mean wind velocity. Unlike flow in the inertial layer, it was observed that heat fluxes are significant in all the three directions and are always positive.