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High-Fidelity Numerical Modeling of UV-Based Mitigation Strategies for Airborne Virus transmissions in Enclosed Spaces

ED MEGEP – [Subject to defense authorization]

https://youtube.com/live/lNuICpBOPxQ?feature=share

The mitigation of airborne virus transmission in enclosed environments, such as public transportation, has become a critical area of research in light of recent global pandemics, including COVID-19. Ultraviolet (UV) air purifiers have emerged as a recommended strategy to deactivate airborne viruses and reduce infection spread in such spaces. This study develops a high-fidelity computational framework to assess the efficacy and effectiveness of UV air purifiers in reducing the spread of virus-laden droplets. Large Eddy Simulations (LES) are employed to resolve turbulent flow dynamics inside the purifier, with two UV lamps activated under specified operating conditions. Once a statistically converged Eulerian flow is achieved, time-averaged velocity and temperature distributions are used in a one-way coupled Eulerian-Lagrangian framework to model the turbulent dispersion of virus-laden droplets. The simulations incorporate an evaporation model, highlighting the importance of this physical phenomenon, as the majority of droplets exiting the purifier are identified as droplet nuclei containing non-volatile matter and virus copies. The survival rate of these droplets is then assessed using a UV radiation disinfection solver, validated against experimental studies, indicating that the UV air purifier achieves a 99% inactivation rate, demonstrating its potential as an effective mitigation strategy.

The study further investigates the placement of UV purifiers in a city bus to study their efficiency in inactivating airborne viruses. Simulations explore various purifier configurations, employing a Lagrangian particle tracking approach to model droplet dispersion and interaction with airflow. The results reveal that placing the purifier in the middle of the bus yields the highest inactivation rates, minimizing airborne and surface contamination. The rear placement also proves effective, especially in reducing virus-laden droplets from rear-seated passengers. In contrast, the front placement is less efficient due to recirculation patterns limiting its impact on droplet interception. The study also demonstrates that increasing the volumetric flow rate of the purifier beyond 100 m³/hr can significantly improve viral inactivation. Optimizing purifier placement is an effective strategy for enhancing air quality. Additionally, the deployment of two purifiers—one in the middle and one at the rear—can further enhance air purification, ensuring uniform air quality throughout the bus. These findings underscore the potential of UV air purifiers as a viable intervention for reducing airborne pathogen concentrations, providing crucial insights for air quality management in public transportation and other high-occupancy indoor spaces.

Jury

Talib DBOUK	Université de Rouen	Reviewer
Jeanne MALET	IRSN	Reviewer
Guillaume BALARAC	LEGI Grenoble	Examiner
Simon MENDEZ	Université de Montpellier	Examiner
Nicolas FRANCOIS	Valéo Thermal Systems	Invited member
Florent Duchaine	Cerfacs	Thesis supervisor
Thierry Poinsot	Cerfacs	Thesis co-supervisor