A CFD Model Intercomparison and Validation using High Resolution Wind Tunnel Data

A joint modeling effort to develop a multiscale urban building transport and dispersion capability is being undertaken by Los Alamos and Lawrence Livermore National Laboratories. This joint effort exploits the current rapid advances in parallel computing technology and numerical methods to extend current modeling capabilities at both labs toward the full range of urban modeling regimes. These regimes include small scale, high resolution simulations of flow and dispersion around highly resolved building complexes, to larger scale domains involving hundreds of buildings spanning numerous city blocks. As part of this development effort, CFD model simulations employing Reynolds-average (RANS) and Large Eddy Simulation (LES) representations of turbulence from two independently developed models are validated using recent high resolution wind tunnel data. The wind tunnel data consists of mean and turbulent velocity statistics, and tracer concentration data, obtained from the USEPA Fluid Modeling Facility. The data were obtained for rectangular arrays of blocks arranged in patterns consisting of long rows arranged perpendicular to the free flow wind direction, or regularly spaced cubical buildings. The relative merits of modeling techniques (ie., RANS vs. LES), numerical procedures, and physical parameterizations, and their effect on model performance in predicting the observed flow features, are presented.