A CFD study of the transport and fate of airborne droplets in a ventilated office: The role of droplet−droplet interactions

Highlights

• Coulomb and Lennard−Jones forces were considered for droplet interactions.

• The net droplet interactions were repulsive.

• Repulsive droplet interactions increased the transport of droplets.

• Repulsive droplet interactions significantly modified the fate of droplets.

Abstract

Previous studies reported that specially designed ventilation systems provide good air quality and safe environment by removing airborne droplets that contain viruses expelled by infected people. These water droplets can be stable in the environment and remain suspended in air for prolonged periods. Encounters between droplets may occur and droplet interactions should be considered. However, the previous studies focused on other physical phenomena (air flow, drag force, evaporation) for droplet transport and neglected droplet interactions. In this work, we used computational fluid dynamics (CFD) to simulate the transport and fate of airborne droplets expelled by an asymptomatic person and considered droplet interactions. Droplet drag with turbulence for prediction of transport and fate of droplets indicated that the turbulence increased the transport of 1 μm droplets, whereas it decreased the transport of 50 μm droplets. In contrast to only considering drag and turbulence, consideration of droplet interactions tended to increase both the transport and fate. Although the length scale of the office is much larger than the droplet sizes, the droplet interactions, which occurred at the initial stages of release when droplet separation distances were shorter, had a significant effect in droplet fate by considerably manipulating the final locations on surfaces where droplets adhered. Therefore, it is proposed that when an exact prediction of transport and fate is required, especially for high droplet concentrations, the effects of droplet interactions should not be ignored.

Graphical abstract

Keywords

Droplet interactions / Aerosols / Colloids / CFD / Transport / Fate

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Acknowledgements

This work was supported by the Brain Pool Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT, Republic of Korea (No. 2019H1D3A2A02101993).

Conflict of Interest

The authors do not have conflicts of interest to declare.

Author Contributions

Allan Gomez-Flores: Methodology, Investigation, Software, Writing − Original draft preparation. Gukhwa Hwang: Writing − Original draft preparation. Sadia Ilyas: Writing − Reviewing and Editing. Hyunjung Kim: Conceptualization, Supervision, Writing − Reviewing and Editing.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-021-1465-8 and is accessible for authorized users.

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