Modelling aerosol transport and virus exposure with numerical simulations in relation to SARS-CoV-2 transmission by inhalation indoors

TL;DR

This study uses physics-based modeling and simulations to investigate aerosol dispersion and virus exposure indoors, providing insights into SARS-CoV-2 airborne transmission potential and exposure times.

Contribution

It introduces a comprehensive modeling framework combining CFD and Monte Carlo simulations to quantify aerosol transport and inhalation risk indoors.

Findings

Aerosols smaller than 20 microns can linger for about an hour, enabling inhalation.

Large droplets up to 100 microns rapidly dry into aerosols, increasing airborne risk.

Exposure times to inhaling significant aerosol quantities can range from seconds to hours.

Abstract

We provide research findings on the physics of aerosol dispersion relevant to the hypothesized aerosol transmission of SARS-CoV-2. We utilize physics-based modeling at different levels of complexity, and literature on coronaviruses, to investigate the possibility of airborne transmission. The previous literature, our 0D-3D simulations by various physics-based models, and theoretical calculations, indicate that the typical size range of speech and cough originated droplets (d < 20microns) allows lingering in the air for O(1h) so that they could be inhaled. Consistent with the previous literature, numerical evidence on the rapid drying process of even large droplets, up to sizes O(100microns), into droplet nuclei/aerosols is provided. Based on the literature and the public media sources, we provide evidence that the infected individuals could have been exposed to aerosols/droplet nuclei by inhaling them in significant numbers e.g. O(100). By 3D computational fluid dynamics (CFD) simulations, we give examples on the transport and dilution of aerosols (d<20microns) over distances O(10m) in generic environments. We study susceptible and infected individuals in generic public places by Monte-Carlo modeling. The model accounts for the locally varying aerosol concentration levels which the susceptible accumulate via inhalation. The introduced concept, 'exposure time' to virus containing aerosols is proposed to complement the traditional 'safety distance' thinking. We show that the exposure time to inhale O(100) aerosols could range from O(1s) to O(1min) or even to O(1h) depending on the situation. The Monte Carlo analysis provides clear quantitative insight to the exposure time in different public indoor environments.