Computational Parametric Study to Improve Air Quality in High-Density Cities

In high density mega cities, air pollution has a higher impact on public health than cities of lower population density. Apart from higher pollution emissions due to human activities of densely populated street canyons, stagnated air flow due to closely packed tall buildings result in lower dispersion potentials. The coupled result leads to high air pollution concentrations being reported frequently at street side stations in Hong Kong. High density urban morphologies need to be carefully designed to lessen the ill effects of high density urban living. This study addresses the knowledge-gap between planning and design principles and air pollution dispersion potentials in high density cities. The air ventilation assessment understandings for high density planning and design are advanced to relate the air pollutant dispersion issues. The methods in this study are CFD simulation and parametric study. The SST κ- ω model is adopted after balancing the accuracy and computational cost in the comparative study. Urban-scale parametric studies are conducted to clarify the effects of urban permeability and building geometries on air pollution dispersion, for the outdoor pedestrian environment. Given the finite land resources in high-density cities and the numerous planning and design restrictions for development projects, the performance of mitigation strategies is evaluated to optimize the benefits. A real urban case study is conducted to demonstrate that suggested design strategies are feasible in the urban design.