Combined strategies of void layout and urban planning on air ventilation and pollutant removal in deep canyons

The perceptiveness and implementation of enhancing city breathability and urban air quality are crucial to attain a more resilient built environment. This study conducts the CFD parametric analysis to evaluate the relations of varied void layouts and urban patterns with ventilation performance for pollution mitigation. To provide the helpful guidelines in the planning and design of street canyons toward more sustainable cities, the indices of ACH and ACH_PFR are thoroughly analyzed to appraise the improvement of urban aeration and control of pollutant dispersal. The placement of 12.5 m × 12.5 m voids at a height of 45 m on upstream buildings can increase the air exchange rate and purging flow rate by 20.4% and 24.5% in comparison to those without voids. The strategy of incorporating concentrated square voids into upstream buildings at medium heights can realize the percentage increases of 51.5% in ACH and 188.1% in ACH_PFR, promoting city breathability and sustainable development in dense urban environments.