Award Date

August 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Committee Member

Yi-Tung Chen

Second Committee Member

Lung-Wen Chen

Third Committee Member

Hui Zhao

Fourth Committee Member

Jeremy Cho

Fifth Committee Member

Eakalak Khan

Sixth Committee Member

Mark Buttner

Number of Pages

126

Abstract

This dissertation has explored computational fluid dynamics (CFD) techniques for studying particulate air quality in the Las Vegas urban area. The dissertation is based on three research tasks: • High time-resolution fenceline air quality sensing and dispersion modeling for environmental justice-centered source attribution. (Chapter 2) • Pollen dispersion and deposition in real-world urban settings: A computational fluid dynamic study. (Chapter 3) • Effects of urban canopy parameterizations on modeling pollen dispersion and exposure. (Chapter 4) In Chapter 2, we investigate the facilitation of low-cost air quality sensors (LCAQS) and CFD technique on exposure assessment of environmental justice (EJ) communities and evaluate the impact from a particular source of air pollution. Based on all five-minute data from the two sensors, Wells Cargo (source of concern) contributed to 3.7% and 11.8% of PM2.5 and PM10 measured at SVHS with daily contributions up to 28% and 50%, respectively. The data reveal strong dependencies of Wells Cargo’s contribution on wind speed, time of day, and day of the week (weekday vs. weekend), consistent with emission activities from aggregate handing in such a facility. An average PM10 emission rate of 0.58 g s-1 and PM10/PM2.5 emission ratio of 11 were also derived for wind speed 10 miles per hour (~4.5 m s-1) according to the modeled source receptor relationships. The emission rate and ratio agree, within 20%, with the National Emission Inventory. CFD-based dispersion modeling shows that Wells Cargo only impacts SVHS when wind direction ranges 270°–112.5°, where its contribution can be quantified by the different measurements between SVHS’s sensor, and another senor installed near Wells Cargo’s northern fenceline representing the urban background. In Chapter 3, this thesis highlights the health and environmental impacts of allergic pine pollen on an urban residential community located in western Las Vegas. A CFD modeling framework based on the Eulerian-Lagrangian approach with mesh grids of <10 meters to simulate the dispersion and deposition of pollen emitted from inventoried pine trees in a real-world urban context. Model results highlighted that building structures constrained pollen transportation by reducing wind speeds, especially during the low period, and altered pollen distributions, creating hot spots and cold spots at the windward and leeward sides of buildings, respectively, on the pollen trajectories. The majority of pollen particles appear to deposit onto the ground or buildings 1–3 kilometers downwind from the sources through gravitational settling. In Chapter 4, aerodynamics roughness length (ARL) has been implemented in different building array configurations to probe the level of biases in the wind flow field and simultaneously, accessing how ARL balances the computational cost and accuracy of the pollen dispersion model. The ARL model gives the contours of spatially-averaged variables similar to the core urban model, where the core-urban model serves as the baseline scenario. The outcomes of the flat-earth model display qualitatively different wind velocity, pollen concentration, and pollen deposition contours from the core urban model and ARL model. Therefore, the thesis focuses on investigating meteorological and transport patterns associated with pollen/dust pollution episodes, particularly near their sources. The model can be most useful for decision-makers during the urban planning process. These outcomes will inform optimal CFD modeling practices to study urban air pollution, particularly dust and pollen pollution near their sources. Such study designs meet the need and resource constraint of environmental justice (EJ) communities and can be readily adapted to generate information that allows stakeholders to take necessary actions to mitigate health risks due to air quality concerns.

Keywords

Air Pollution; CFD; Dispersion; Environmental Engineering; Environmental Justice; Pollen Particles

Disciplines

Aerodynamics and Fluid Mechanics | Engineering | Mechanical Engineering

File Format

pdf

File Size

4850 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/


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