The project planning activities of urban air quality and breathability have increasingly become the noticed issues around the world in recent times. In this study, the incorporation of half-open spaces into the ground corners of high-rise buildings is accomplished by slightly modifying the building morphology as a feasible solution. A unified procedure is proposed via a combined framework of parametric CFD study and multivariable regression analysis to optimize the half-open space design for improving ventilation performance and air quality. The influences of four design parameters on wind flow characteristics are investigated, including (i) the building height, (ii) the width of street canyon, (iii) the height of half-open space, and (iv) the width of half-open space. Using the results from this combined framework, CFD simulations are then extended to inspect the effectiveness of merging optimized half-open space layouts into high-rise buildings as the deterministic analysis in a realistic case study. Both CFD simulations are validated with the wind tunnel data for a generic urban array and on-site measurements for a realistic case study. The predictions are discussed to evaluate the outcomes of urban breathability and air pollutant dispersion by the indices of air change per hour (ACH) and purging flow rate (PFR). The incorporation of optimized half-open spaces into constructions can greatly improve urban ventilation and air pollutant dispersion in the pedestrian pathway layer. To complete the combined framework for a realistic high-rise urban area, the optimized half-open space design can increase ACH* and PFR by 75% and 57%, respectively, in the pedestrian pathway layer, as compared to the case of original half-open space design. This strategy relies on the database formulated from the CFD results of varied building morphologies in the generic urban array to realize the optimized design in a more effective and time-saving manner when applying to realistic cases.
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