QWIC-URB is a fast response model designed to generate high resolution, 3 dimensional wind fields around buildings. Velocity fields are produced with a mass consistent diagnostic wind model that utilizes empirical parameterizations based on the work of Röckle and Kaplan & Dinar. An initial wind field is prescribed (uo,vo,wo) based on a uniform incident flow and the various flow effects associated with building geometries and the ground. These empirical parameterizations for flow around buildings are associated with flow regimes that are a function of building spacing and geometry. The final velocity field (u,v,w) is obtained by forcing the initial velocity field to be mass consistent. For these geometries, the resulting complex 3D velocity field resembles averaged experimental results.

Until now, QWIC-URB has been used for producing wind fields around single buildings with various incident wind angles. For the work presented here, the model has been expanded to consider 3D canyon flow between two buildings. That is, two rectangular parallelepipeds of height H, width W, and length L separated by a distance S. As in Kaplan and Dinar, the canyon flow is parameterized distinctly for two flow regimes: skimming (when S<1.55H for W/H >=2 and <1.55H for W/H <2) and isolated flow. In the skimming regime a simple vortex is imposed between the buildings, while for isolated flow the standard parameterization for a single building are used. That is, an empirical vortex is placed upwind and downwind of the building.

The model is shown to qualitatively predict the flow field well for simple canyon flow. For large W/H, the mass conservation method produces physically significant canyon vortices in the horizontal plane with axis normal to the street surface at each lateral edge of the canyon. These vortices may be an important transport mechanism of pollutants out of the canyon. Results will be compared to experimental data for two building street canyons of varying H, W and L, and S. The model’s ability to handle more complex two building arrangements will also be investigated, including buildings with different relative heights and widths, and buildings that are laterally-offset from one another.