Quantifying dense gas dispersion in urban areas

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Proposal: 1703548PI: Nigel KayeUrban canopies can reduce pollution dispersion, leading to increased local concentrations of pollutants. The physics of dense gas dispersion in urban areas is poorly understood because of the health risks, cost, and measurement resolution limitations of large-scale field studies. One goal of this research is to develop a new laboratory method for safely studying dense gas dispersion in urban areas at a spatial resolution not previously achieved, and use this method to undertake high resolution, statistically rigorous validation of computational models.The research will study the influence of topography-generated turbulence on building-scale mixing of dense gasses trapped in urban canopies. The experimental technique will use simultaneous particle tracking and light-induced fluorescence measurements of salt water being dispersed by a freshwater flow. The simultaneous measurements of the time-varying velocity and density fields will enable the calculation of the turbulent pollutant flux along with all other mean and turbulent properties of the flow. Experimental and published data will be used in a detailed statistical validation study of computational fluid dynamics sub-grid-scale models to assess their ability to model dense gas dispersion. The technique has significant advantages over full-scale testing as it is cheaper, offers greater parameter and boundary condition control and hence greater repeatability, has significantly improved measurement spatial resolution, and does not require releasing dangerous chemicals into the environment. In terms of the broader impacts, the experimental technique developed will transform the study of dense gas dispersion in urban areas through improved spatial and temporal resolution. The measurements will enable the quantification of local mixing processes that are particularly important in geometrically complex regions like urban canopies. The primary societal benefit will be as a tool for responding to emergency dense gas releases in urban areas. The PI has a good track record of recruiting graduate students from underrepresented groups and will work through university programs to recruit minority students for the research team. The research team will work with the PI on educational outreach through the development of physical demonstrations to be used at school outreach events and written up for use by teachers in STEM classes.