Fluid dynamics simulations show that facial masks can suppress the spread of COVID-19 in indoor environments

TL;DR

High-fidelity fluid dynamics simulations demonstrate that facial masks significantly reduce saliva particle spread indoors during coughing, but outdoor airflow can diminish their effectiveness due to leakage and turbulence.

Contribution

This study provides detailed computational analysis of saliva particle transport during coughs, comparing medical and non-medical masks under indoor and outdoor conditions.

Findings

Masks reduce saliva spread indoors, limiting particles to under 0.5 meters.

Outdoor airflow can cause saliva particles to travel farther despite mask use.

Mask effectiveness varies with environmental conditions and airflow patterns.

Abstract

The Coronavirus disease outbreak of 2019 has been causing significant loss of life and unprecedented economical loss throughout the world. Social distancing and face masks are widely recommended around the globe in order to protect others and prevent the spread of the virus through breathing, coughing, and sneezing. To expand the scientific underpinnings of such recommendations, we carry out high-fidelity computational fluid dynamics simulations of unprecedented resolution and realism to elucidate the underlying physics of saliva particulate transport during human cough with and without facial masks. Our simulations: (a) are carried out under both a stagnant ambient flow (indoor) and a mild unidirectional breeze (outdoor); (b) incorporate the effect of human anatomy on the flow; (c) account for both medical and non-medical grade masks; and (d) consider a wide spectrum of particulate sizes, ranging from 10 micro m to 300 micro m. We show that during indoor coughing some saliva particulates could travel up to 0.48 m, 0.73 m, and 2.62 m for the cases with medical-grade, non-medical grade, and without facial masks, respectively. Thus, in indoor environments either medical or non-medical grade facial masks can successfully limit the spreading of saliva particulates to others. Under outdoor conditions with a unidirectional mild breeze, however, leakage flow through the mask can cause saliva particulates to be entrained into the energetic shear layers around the body and transported very fast at large distances by the turbulent flow, thus, limiting the effectiveness of facial masks.