Evaluation of the QUIC-URB Wind Model using Wind-Tunnel Data for Step-Up Street Canyons

The Quick Urban & Industrial Complex (QUIC) dispersion modeling system is comprised of an urban wind model called QUIC-URB, a Lagrangian dispersion model QUIC-PLUME and a graphical user interface QUIC-GUI. QUIC-URB computes spatially-resolved mean wind fields in urban domains and is based on empirical flow parameterizations and mass conservation. The basic parameterizations in QUIC-URB have been developed using existing wind-tunnel data sets for simple buildings arrangements such as isolated buildings and street canyons. For more complex building configurations, these parameterizations are applied by dividing a complex building configuration into series of simple (rectangular parallelepiped-shaped) building configurations and superimposing the resulting flow fields. In the present paper, one such parameterization, namely, the street-canyon parameterization is evaluated for step-up canyons. A step-up canyon is defined as a street canyon in which the height of the upwind building is less than the height of the downwind building. In this paper, the QUIC-URB model is evaluated against a series of wind-tunnel experiments run at the Environmental Fluid Dynamics Laboratory at the University of Utah. Specifically, eight cases were considered for normal incident shear flow with several different upwind and downwind building heights and several different cross-wind building widths. Changes in the mean mean flow patterns along the centerline of the street canyon for the different cases were studied. Model-computed results were compared with the experimental data. For wide step-up canyons, the QUIC-URB wind model was not able to predict: 1) the formation of a secondary counter-rotating vortex near the base of the canyon and 2) a strong downdraft on the windward face of the downwind building that compresses the classical street canyon vortex against the leeward face of the upstream building in the street canyon. A new parameterization for step-up street canyons will be developed using data from the aforementioned experiments.