  We present high-fidelity numerical simulations of expiratory biosol transport
during normal breathing under indoor, stagnant air conditions with and without
a facial mask. We investigate mask efficacy to suppress the spread of saliva
particles that is underpinnings existing social distancing recommendations. The
present simulations incorporate the effect of human anatomy and consider a
spectrum of saliva particulate sizes that ranges from 0.1 micrometers to 10
micrometers while accounting also for their evaporation. The simulations
elucidate the vorticity dynamics of human breathing and show that without a
facial mask, saliva particulates could travel over 2.2 m away from the person.
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 facial masks can successfully suppress the spreading
of saliva particulates due to normal breathing in indoor environments.
