Quantifying dense gas dispersion in urban areas

建议：1703548 PI：奈杰尔凯耶城市树冠可以减少污染扩散，导致污染物的局部浓度增加。由于大规模实地研究的健康风险、成本和测量分辨率的限制，人们对城市地区稠密气体扩散的物理学知之甚少。本研究的一个目标是开发一种新的实验室方法，以安全地研究城市地区的稠密气体扩散，其空间分辨率以前从未达到过，并使用这种方法进行高分辨率，统计上严格验证的计算模型。本研究将研究地形产生的湍流对城市树冠中稠密气体混合的影响。该实验技术将同时使用粒子跟踪和光诱导荧光测量盐水被淡水流分散。同时测量随时间变化的速度和密度场将能够计算湍流污染物通量沿着流的所有其他平均和湍流特性。实验和公布的数据将用于计算流体动力学亚网格尺度模型的详细统计验证研究，以评估其模拟致密气体扩散的能力。该技术与全尺寸测试相比具有显著优势，因为它更便宜，提供更大的参数和边界条件控制，因此具有更高的可重复性，显著提高了测量空间分辨率，并且不需要将危险化学品释放到环境中。 就更广泛的影响而言，开发的实验技术将通过提高空间和时间分辨率，改变城市地区稠密气体扩散的研究。这些测量将能够量化局部混合过程，这在城市树冠等几何复杂地区尤为重要。 主要的社会效益将是作为应对城市地区紧急高密度气体释放的工具。 PI在从代表性不足的群体中招募研究生方面有着良好的记录，并将通过大学项目为研究团队招募少数民族学生。研究团队将与PI合作，通过开发物理演示来进行教育推广，这些演示将用于学校推广活动，并编写供STEM课程的教师使用。

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.