A study on uneven street canyons on air flows and and pollutant dispersion along Taft avenue using CFD

• Main Author: Gonzales, Zyrille Ann Asido
• Format: text
• Language: English
• Published: Animo Repository 2024
• Subjects: Computational fluid dynamics; Air—Pollution > Philippines > Manila; Physics
• Online Access: https://animorepository.dlsu.edu.ph/etdb_physics/25; https://animorepository.dlsu.edu.ph/context/etdb_physics/article/1044/viewcontent/2024_Gonzales_A_Study_on_Uneven_Street_Canyons_on_Air_Flows_and_and_Pollutant_D.pdf
• Institution: De La Salle University

This study focuses on assessing air pollution dispersion within street canyons, specifically along Taft Avenue in Metro Manila. The accumulation of pollutants in the city poses significant health risks in urban environments. By simulating airflow patterns and pollutant dispersion using computational fluid dynamics (CFD) models, this research aims to identify areas of high pollution concentration and hotspots. The methodology involves creating the model of Taft Avenue using Onshape CAD software, covering approximately 346 meters of the street canyon. A computational domain of 6, 4 and 6H height, width and length respectively is defined around the street canyon. The standard k-epsilon (k-ε) turbulence model is implemented in ANSYS Fluent, along with species transport models for pollutant dispersion. Mesh generation and boundary condition setup are implemented to analyze airflow along Taft Avenue. Mesh settings are adjusted to a finer resolution (from 40m to 3m), ensuring accurate representation of the geometry. Boundary conditions at the inlet specify a uniform velocity magnitude of 0.6 m/s, turbulent intensity of 10%, temperature of 300 Kelvin, and oxygen species concentration of 23%. The study shows that pollutant concentrations are higher near the road and under the LRT, particularly in street canyons and on the downwind side where pollutants are trapped by building walls. Windward areas experience lower pollution due to direct wind impact, creating high-pressure zones that disperse pollutants away from building surfaces. Ground-level recirculation zones trap pollutants, but their concentrations are lower due to more effective wind dispersion. Pollutants emitted by vehicles under the LRT become concentrated in these recirculation zones due to the physical barrier created by the LRT structure. Temperature differences, such as those from solar-heated building surfaces, contribute to vortex formation, further affecting pollutant dispersion.