Abstract
Face masks are used widely to mitigate the spread of infectious diseases. While their main purpose is 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 the presence of a mask by tracking the air exhaled by a person through a mask, using both infrared imaging and particle image velocimetry performed on illuminated fog droplets surrounding a subject. We show how a mask confines the exhaled flows within tens of centimeters in front of a person breathing or speaking. In addition, we show that the tissue of common surgical face masks has a low permeability, which efficiently transforms the jetlike flows of exhalation produced during breathing or speaking into quasivertical buoyancy-driven flows. Therefore, wearing a mask offers a strong mitigation of direct transport of infectious material in addition to providing a filtering function. By comparing results on human subjects and model experiments, we propose a model to rationalize how a mask changes the air flow, and thus we provide quantitative insights that are useful for descriptions of disease transmission.
- Received 29 June 2021
- Accepted 4 October 2021
DOI:https://doi.org/10.1103/PhysRevFluids.6.110511
©2021 American Physical Society
Physics Subject Headings (PhySH)
Collections
This article appears in the following collection:
Fluid Mechanics of Infectious Diseases Invited Papers
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.
synopsis
Altering Airflows and Stopping Drops
Published 23 November 2021
Two new studies provide insights into the efficacy of masks under different usage conditions, results that could help improve strategies for lowering transmission of COVID-19.
See more in Physics