Large-eddy simulation of human respiratory events with and without facial mask *

The Coronavirus disease outbreak of 2019 has been causing significant loss of life and unprecedented economic 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 large-eddy simulations, along with Lagrangian and Eulerian particle transport approaches, of unprecedented resolution to elucidate the underlying physics of saliva particulate transport during human breathing and without facial masks. We elucidate the vortex dynamics of human breathing and show that saliva particulates could travel over 2.2 m away from the person without a mask. However, a non-medical grade face mask can drastically reduce saliva particulate propagation to 0.72 m away from the person. This study provides new quantitative evidence that facile masks can successfully suppress the spreading of saliva particulates due to normal breathing in indoor environments.