First Advisor

Xiaowei Zhu

Term of Graduation

Summer 2026

Date of Publication

8-12-2026

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Mechanical Engineering

Department

Mechanical and Materials Engineering

Language

English

Subjects

Computational fluid dynamics, ENVI-met, Local Climate Zones, PM2.5 dispersion, Street canyon ventilation, Urban morphology

Physical Description

1 online resource (viii, 67 pages)

Abstract

Urban form exerts strong control on how pollution from outside a city is transported through the urban canopy and experienced at street level. This study uses the prognostic microclimate model ENVI-met to simulate an active pollutant released from an upwind rural highway and advected through an urban region represented by ten Local Climate Zone (LCZ) types. The cases share identical inflow and are isothermal, dry, and non-vegetated, so that differences among them are attributable to building morphology alone. PM2.5 is the primary exposure diagnostic. Its transport and ejection are characterized through plan-view contours, vertical plume sections, and spatially averaged streamwise profiles, which reveal three competing controls: streamwise channeling, lateral exchange at cross streets, and morphology-dependent vertical redistribution. The strength of these controls reverses between the compact and open building families, so pedestrian-level concentration does not vary monotonically with building height. A four-stage regression framework of pairwise linear regression, principal component analysis, spatial refinement, and a refined regression links morphological parameters to dispersion. A single principal component, on which building volume density, frontal area index, and aspect ratio load positively and sky view factor negatively, captures most of the predictor variance and is associated with elevated street-level concentration, strongest at the first upwind spanwise canyon. Building surface fraction (BSF) yields no significant regression relationship, but analysis shows that higher BSF promotes stronger spanwise ejection. These results indicate that exposure assessment for upwind sources should weight the upwind building row over bulk interior statistics.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/45147

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