Sombuddha Bagchi, Saptarshi Basu, Swetaprovo Chaudhuri, and Abhishek Saha
Phys. Rev. Fluids 6, 110510 (2021) – Published 23 November, 2021
Physical Review Fluids publishes a collection of papers associated with invited talks presented at the mini-symposium on the Fluid Mechanics of Infectious Diseases at the 73nd Annual Meeting of the APS Division of Fluid Dynamics.
We present a study of wetted facemasks to evaluate their capability in blocking respiratory droplets. We show that the increase in wetness progressively weakens the penetration capability of the impacted droplets. Such behavior is observed for hydrophobic and hydrophilic masks, although the underlying mechanism is different.
In addition to their ability to filter pathogenic droplets, masks also represent a porous barrier to exhaled and inhaled air flow. In this study, we characterize the aerodynamic effect of a mask by tracking the air exhaled by a person through a mask. We show how a mask confines the exhaled flows within tens of centimeters in front of a person breathing or speaking.
Increasing the ventilation airflow speed is commonly assumed to decrease the probability of airborne infectious disease transmission, since higher airflow means more fresh air and lower concentrations of airborne pathogens. Here we demonstrate experimentally that increasing the airflow speed by a factor of 10 had no impact on the probability of influenza transmission between guinea pigs. We use perfect-mixing and Gaussian plume models to interpret this result as evidence that the virus is primarily carried on virus-contaminated dust, rather than in expiratory aerosols as commonly assumed.
