Large eddy simulations to investigate airborne virus inactivation using a ultraviolet air purifier with Lagrangian tracking

In response to the recent COVID-19 pandemic, Ultraviolet (UV) air purifiers have emerged as a recommended mitigation strategy to deactivate airborne viruses and reduce infection spread within enclosed spaces. This paper focuses on developing a high fidelity computational methodology to investigate the efficacy of such devices. Large Eddy Simulations are used to resolve the turbulent flow inside the purifier with 2 UV lamps activated for specified operating conditions. A fully coupled, or two-way coupling approach, is compared with a computationally efficient one-way coupling method. Once the Eulerian flow reaches statistical convergence, time-averaged velocity and temperature distributions are extracted and provided to an Eulerian–Lagrangian framework to examine the turbulent dispersion of virus-laden droplets based on a frozen flow approach. These simulations incorporate an evaporation model for virus-laden droplets, highlighting the importance of accounting for this physical phenomenon. The majority of droplets exiting the purifier are identified as droplet nuclei containing non-volatile matter and virus copies. The survival rate of these expelled virus-laden droplets is determined using a UV radiation disinfection solver, developed and validated based on existing experimental studies. The resulting inactivation rate of the UV air purifier reaches 99%, highlighting its potential as an effective mitigation strategy.