Detailed magnetic resonance imaging measurements of a contaminant dispersed in an Oklahoma City model

Magnetic resonance imaging techniques were used to collect time-averaged three-component velocity and concentration data across a scaled model of 2003 Oklahoma City. The experiments included the release of a passive scalar designed to mimic the field tests of the Joint Urban 2003 (JU03) study conducted at the same site and provide measurements throughout the entire three-dimensional domain in nearly 10 million locations. The flow was in a fully turbulent water channel with a Reynolds number of 36,000 based on the channel hydraulic diameter. The geometrically similar cityscape was on the bottom wall of the channel. A low-momentum injector was designed to release the contaminant at the intersection of Broadway and Main street – a location that closely matches the Intense Observation Period 8 of JU03, which has been previously examined in several studies. Magnetic Resonance Velocimetry (MRV) and Magnetic Resonance Concentration (MRC) techniques measured the time averaged field with experimental uncertainties of 5.5% and 4% respectively, providing a candidate validation data set for atmospheric flow models. The inflow velocity boundary condition was measured at the inlet plane of the test section. Detailed analysis is provided of the flow field and concentration distribution, focusing on major features in the downtown area. In addition, a comparison with the available field test data near surface locations is conducted. The measurements are believed to be amongst the first of their kind and suggest that MRV/MRC techniques may be an effective means to study the flow and scalar dispersion within urban environments.