High-Fidelity Simulations of Contaminant Dispersion in an Urban Environment with Comparison to Magnetic Resonance Imaging Measurements

Abstract The dispersion of a contaminant in an urban environment has the potential to impact a large population of people. In this work, a complex urban canopy flow based on the Oklahoma City downtown business district circa 2003 is studied using Magnetic Resonance Imaging (MRI) and high-fidelity Large Eddy Simulations (LES). MRI is a novel experimental technique that can provide high-resolution measurements in four dimensions (three spatial and temporal) for lab scale models. The experiments and simulations use the same geometry and boundary conditions providing a one-to-one comparison of the two methods. Results are presented on the time-averaged velocity and concentration fields, the temporal dynamics of the concentration plumes for a transient release, and a novel Cloud Identification Algorithm (CIA) that can separate plumes produced by periodic contaminant releases used for ensemble averaging over many releases. The MRI and LES datasets agree very well and identify complex flow features within the urban environment.