Testing of a Far-wake Parameterization for a Fast Response Urban Wind Model

The Quick Urban & Industrial Complex (QUIC) dispersion modeling system has been developed to rapidly provide 3D wind and concentration fields in cities and around building complexes. The fast response 3D urban wind model QUIC-URB explicitly solves for the flow field around buildings using a suite of empirical parameterizations and mass conservation. Previous evaluations of the model against single and multiple building wind-tunnel data sets have shown weaknesses in several of the standard parameterizations. In particular, the far-wake velocity-deficit region does not compare well with experimental results. Since QUIC-URB does not solve momentum equations, there is no mechanism in the model to produce momentum diffusion. To overcome this problem, algorithms for diffusing momentum in the horizontal and vertical directions were implemented into the code by using a shelter model with a Gaussian-shaped envelope. The QUIC-URB output was then compared with measurements obtained in the USEPA meteorological wind tunnel for a variety of buildings with different aspect ratios. The implemented algorithms significantly improved the prediction of velocity distributions in the far wake. In this presentation, the new wake diffusion scheme will be described and comparisons to experimental data will be shown.