Pollutant cross-transmission in courtyard buildings: Wind tunnel experiments and computational fluid dynamics (CFD) evaluation

Sun, Hao; Owen, John S.; Almazmumi, Salah; Liu, Chong; Mohammadi, Murtaza; Dik, Abdullah; Jimenez-Bescos, Carlos; Calautit, John Kaiser

Abstract

Courtyards, a historical architectural feature surrounded by buildings, are common in urban housing and residential complexes. These spaces, often open-air and with rooms facing them, are crucial for daylight and natural ventilation. While courtyards are essential for introducing fresh airflow into adjacent indoor areas, the effectiveness of natural ventilation may be compromised due to potentially poor air circulation from limited openings. This raises a significant concern: could the design of courtyards inadvertently facilitate pollutant cross-transmission? Despite a wealth of research focused on airflow within courtyards, the indoor spaces in proximity to these courtyards have often been neglected in previous works, particularly concerning the exchange of pollutants between the indoor and courtyard environment. This research investigates the dynamics of indoor-outdoor pollutant cross-transmission in courtyard buildings, assessing factors like external wind flow patterns and internal pollutant sources. Wind tunnel experiments were conducted to measure internal pressure and CO2 concentration and to validate a computational model of the courtyard with 12 rooms. The validated Computational Fluid Dynamics (CFD) models were used to simulate the dispersion of pollutants from internal rooms under different wind conditions. The results showed that the k-epsilon Realizable model accurately simulated internal surface pressure distribution and pollutant dispersion in the courtyard building. It was observed that when pollutants were released from the downwind east-facing ground floor room, CO2 concentrations in adjacent side rooms on the same floor were significantly higher, increasing from the baseline of 400 ppm and reaching up to 3211 ppm in the north-facing room at a wind speed of 4.51 m/s and wind direction of 0°. Conversely, when pollutants originated from north- and south-facing side rooms, pollutants were minimally dispersed to adjacent rooms. Furthermore, at a wind direction of 45°, pollutants from wind-exposed rooms predominantly dispersed to downwind rooms, with peak concentrations exceeding 2400 ppm in downwind rooms. These findings demonstrate that pollutant dispersion is highly dependent on wind direction and the location of the pollutant source. The study concludes that while courtyards enhance indoor environmental quality through natural ventilation, their design must be carefully considered to prevent unintended pollutant cross-transmission, particularly under varying wind conditions and pollutant source locations.

Citation

Sun, H., Owen, J. S., Almazmumi, S., Liu, C., Mohammadi, M., Dik, A., Jimenez-Bescos, C., & Calautit, J. K. (2024). Pollutant cross-transmission in courtyard buildings: Wind tunnel experiments and computational fluid dynamics (CFD) evaluation. Building and Environment, 264, Article 111919. https://doi.org/10.1016/j.buildenv.2024.111919

• Journal Article Type: Article
• Acceptance Date: Aug 4, 2024
• Online Publication Date: Aug 6, 2024
• Publication Date: Oct 1, 2024
• Deposit Date: Aug 21, 2024
• Publicly Available Date: Aug 22, 2024
• Journal: Building and Environment
• Print ISSN: 0360-1323
• Electronic ISSN: 1873-684X
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 264
• Article Number: 111919
• DOI: https://doi.org/10.1016/j.buildenv.2024.111919
• Keywords: Courtyard buildingIndoor-outdoor pollutant cross-transmissionAir quality, Wind tunnel experiments, Computational fluid dynamics (CFD)
• Public URL: https://nottingham-repository.worktribe.com/output/38383302
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0360132324007613?via%3Dihub
• Additional Information: This article is maintained by: Elsevier; Article Title: Pollutant cross-transmission in courtyard buildings: Wind tunnel experiments and computational fluid dynamics (CFD) evaluation; Journal Title: Building and Environment; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.buildenv.2024.111919; Content Type: article; Copyright: © 2024 The Authors. Published by Elsevier Ltd.