Iranian Sustainable Building Scientific Association International Journal of Urban Management and Energy Sustainability 2538-1628 7 2 2026 04 01 CFD Simulation of Airflow and Pollutant Dispersion in Urban Street Canyons with Different Building Setback Configurations 196 212 738407 10.22034/ijumes.2026.2093831.1382 EN Zohreh Deymad Department of Urban Planning and Architecture, Yas.C., Islamic Azad University, Yasuj, Iran 0009-0006-9430-1788 Hamideh Jafari Department of Art and Architecture, ST.C., Islamic Azad University, Tehran, Iran 0009-0006-9430-1788 Ali Aram Department of Civil Engineering, Yas.C., Islamic Azad University, Yasuj, Iran 0000-0002-3007-8429 Journal Article 2026 04 20 Air quality in urban open spaces is significantly shaped by urban morphology, airflow behavior, and pollutant emission sources, and it plays a critical role in protecting public health and improving the thermal comfort of urban residents. Accordingly, this study addresses the problem of how building setback position and configuration influence airflow and traffic-related pollutant distribution in urban street canyons, with the aim of identifying the most effective geometric arrangements for improving outdoor air quality. Research methodology in this study is based on a computational fluid dynamic CFD-based numerical simulation to evaluate airflow behavior and pollutant dispersion under different street-canyon configurations. In this framework, building setback position and configuration were treated as the independent variables, while airflow velocity and pollutant concentration were considered the main indicators of air quality. The analysis included one reference canyon without setbacks and nine alternative cases with different setback arrangements on the opposing building facades. The findings show that the street-center region had the highest level of pollutant accumulation because of weaker ventilation conditions, whereas the windward-sidewalk region generally benefited from more favorable airflow patterns. The results also demonstrate that setback configuration plays a decisive role in air-quality performance. Among all examined cases, the best-performing configuration increased the overall mean airflow velocity by 52.4% and reduced the overall mean pollutant concentration by 25.8% compared with the reference case. In addition, this configuration achieved local pollutant reductions of 46.9% at the windward sidewalk and 36.8% at the street center. https://www.ijumes.com/article_738407_b96a867fb4fc066685a676ab10459e0f.pdf