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Air Pollution Dispersion Study in a Diverse Land-Use Urban Area Using Numerical Simulation

Moradpour, Maryam | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53499 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Hosseini, Vahid
  7. Abstract:
  8. Air pollution modeling is a powerful and low-cost tool for taking appropriate strategies to control air pollution. In this research, the effects of vegetation on air pollutant dispersion were studied using computational fluid dynamics models. At the beginning, aerodynamics and thermal effects of vegetation on reactive pollutant dispersion including NO, NO2 and O3 under photochemistry cycle were investigated in two different geometries. In the first geometry, tree planting in an urban environment involving several canyons was simulated. Results show that tree planting causes flow reversal, temperature decrease, and concentration field change. Concentration change of each pollutant not only depends on the aspect ratio (H/W) of the studied site but also on leaf area density (LAD) of vegetation, and the interaction of these parameters is determinant for selecting optimum case of air quality and thermal comfort. From the simulation results of the next geometry, it can be found that the effects of roof greening in shallower canyons are low and limited to pollutant distribution. But, in deeper canyon with H/W=2, different flow structure within canyon makes higher temperature decrease. In this case, the average turbulence kinetic energy increases with increasing LAD; consequently, ventilation efficiency of NOx increases.Furthermore, the impacts of a large park (the Pardisan park in the city of Tehran) on air quality of its surrounding neighborhood which consists of a residential area with major traffic highways on all sides were investigated as a case study. CFD simulations were employed to model the dispersion of pollutants including PM10, CO, NOx and VOC. Results show that trees in the park decrease pollutant concentrations at the pedestrian level, but the relative changes of pollutant concentrations depend on wind direction, deposition velocity of the species and background concentration. The best improvement of air quality was achieved on PM10 with 9%.
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Vegetation ; Air Pollution Modeling ; Dispersion Modeling ; Pollutants Dispersion ; Photochemistry Cycl ; Numerical Analysis

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