Airborne transmission of pathogen-laden expiratory droplets in open outdoor space

Yang, X., Yang, H., Ou, C., Luo, Z. ORCID: https://orcid.org/0000-0002-2082-3958 and Hang, J. (2021) Airborne transmission of pathogen-laden expiratory droplets in open outdoor space. Science of the Total Environment, 773. 145537. ISSN 0048-9697 doi: 10.1016/j.scitotenv.2021.145537

Abstract/Summary

Virus-laden droplets dispersion may induce transmissions of respiratory infectious diseases. Existing research mainly focuses on indoor droplet dispersion, but the mechanism of its dispersion and exposure in outdoor environment is unclear. By conducting CFD simulations, this paper investigates the evaporation and transport of solid-liquid droplets in an open outdoor environment. Droplet initial sizes (dp=10m, 50m, 100m), background relative humidity (RH=35%, 95%), background wind speed (Uref=3m/s, 0.2m/s) and social distances between two people (D=0.5m, 1m, 1.5m, 3m, 5m) are investigated. Results show that thermal body plume is destroyed when the background wind speed is 3m/s (Froude number Fr~10). The inhalation fraction (IF) of susceptible person decreases exponentially when the social distance (D) increases from 0.5m to 5m. The exponential decay rate of inhalation fraction (b) ranges between 0.93 and 1.06 (IF=IF0e-b(D-0.5)) determined by the droplet initial diameter and relative humidity. Under weak background wind (Uref=0.2m/s, Fr~0.01), the upward thermal body plume significantly influences droplet dispersion, which is similar with that in indoor space. Droplets in the initial sizes of 10m and 50m disperse upwards while most of 100m droplets fall down to the ground due to large gravity force. Interestingly, the deposition fraction on susceptible person is ten times higher at Uref=3m/s than that at Uref=0.2m/s. Thus, a high outdoor wind speed does not necessarily lead to a smaller exposure risk if the susceptible person locating at the downwind region of the infected person, and people in outdoors are suggested to not only keep distance of greater than 1.5m from each other but also stand with considerable angles from the prevailing wind direction.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/95854
Identification Number/DOI	10.1016/j.scitotenv.2021.145537
Refereed	Yes
Divisions	Interdisciplinary Research Centres (IDRCs) > Walker Institute Science > School of the Built Environment > Urban Living group Science > School of the Built Environment > Energy and Environmental Engineering group
Publisher	Elsevier
Download/View statistics	View download statistics for this item