Time-resolved Three-dimensional Measurements of Scalar Dispersion from Two Transient Sources in a Mock Urban Geometry

The study of atmospheric dispersion in the urban environment is complicated by building geometries, changing conditions, street canyons, and a variety of other factors. Further complexity is introduced by contaminant releases involving multiple close sources. Magnetic Resonance Imaging (MRI) techniques were applied to a mock urban geometry with two simultaneous transient contaminant releases as a means to provide experimental results with well qualified boundary conditions that can be leveraged to improve simulations of similar flows. The MRI techniques produced three-component velocity and concentration measurements, arranged in a three-dimensional array comprised of over 2.5 million measurement locations for each of 14 successive time intervals within the periodic transient release cycle. The spatial resolution of the measurements provides insight into complex flow and dispersion mechanisms, while the time-resolved nature of the measurements enables analysis of fundamental transport mechanisms. The data sets are expected to be of particular utility for computational fluid dynamics (CFD) model evaluation and validation, as well as for the testing of source term estimation methods. An investigation of the detailed experimental results is presented, demonstrating particular advantages of the dataset towards model comparison efforts.