Computational Prediction of COVID-19 Transmission in Internal Air-Conditioned Environments

Abstract

COVID-19 has had destructive consequences for health, economy and has altered every aspect of everyday human activity. The outbreak was first identified in December 2019 in Wuhan, China. The declaration of the disease as a “Public Health Emergency of International Concern” for the World Health Organization took place on January 30, 2020. Furthermore, 105,5 million cases have been reported until 06 February 2021. Public distancing in internal environments has been applied as a safety measure to prevent transmission. A controversial topic is the safe distance from person to person. The social distancing regulation, for internal public places, has been arbitrarily defined ignoring the potential aerodynamics effects of inlets, such as air-conditioning units, windows and doors. The velocity of the intake airflow has the potential to transfer a droplet from the nose or the mouth of a patient in greater than the indicated distance. The present study focuses on a model of a supermarket that includes a ventilation system and open doors. For the transmission of COVID-19 in an air-conditioned internal space, two different designs were implemented and studied. Internal shelving, furnishing and human models are also being considered. The numerical results obtained are compared with those obtained by two well-known empirical models related to the effective velocity of incoming air and the virus concentration. It is concluded that the computational results obtained in the present study are in acceptable agreement with those obtained by simple empirical models, especially when the standard k-ε model of turbulence is used. Thus, for the cases of coughing and sneezing patients, where we studied the largest particles that sediment onto the floor, the 6-foot (≈1,82 m) rule applies well. However, pathogen-laced particles, coming for example from asymptomatic patients, travel through the air indoors when people breathe and talk. Therefore, there is not much benefit to the 6-foot rule because the air a person is breathing tends to rise and comes down elsewhere, so the person is more exposed to the average background than to a person at a distance. Future research should concentrate rather on the amount of time spent inside rather than distances. As the COVID-19 pandemic is progressing, the present study is flexible and can be applied generally in crowded places. Furthermore, the general outcome is that individuals should maintain the distance of 1,65 meters and it should be applied as guidelines to help reduce the infection risk.