The World Health Organization and the Centers for Disease Control recommend keeping distance between people to prevent the spread of COVID-19. These social distancing recommendations are based on a variety of studies. But further research is needed on the precise mechanisms of virus transport from one person to another.
in Fluid PhysicsResearchers from Stony Brook University, Harvard, ETH Zurich and Hanyang University demonstrate breathing indoors without a mask. It can transport saliva droplets that can transport virus particles at a distance of 2.2 meters or 7.2 feet in 90 seconds.
Using a mask greatly reduces the distance these drops travel. After almost two minutes The saliva restricted by the mask travels only 0.72 meters, below 2.4 feet, and below 1.8 meters, or 6 feet, as recommended by the CDC.
This study used computer simulations with more realistic simulations for the situations of interest than those used in the previous study. The previous task was to transport aerosols after coughing or sneezing. While this study focused specifically on normal human breathing, Normal breathing produces intermittent airflow. with saliva But the speed at which a jet travels is less than a tenth of a cough or sneeze.
The researchers found that even normal breathing creates a complex vortex that can move saliva droplets out of a person’s mouth. The role of these vortexes was never understood before.
Author Ali Khosronejad said: “Our results show that normal breathing without the mask generates a periodic jet and a leading circular vortex ring that propagates forward and interacts with the vortex structures formed in the cyclic vortex. breathe before
This complex vorticity field can transport aerosols over long distances. The mask dissipates the jet’s kinetic energy generated by exhalation. hinder the vortex and limit the movement of virus droplets
The researchers examined the effects of saliva evaporation. In the absence of a mask They found that the droplets of saliva in front of the exhaled breath had partially evaporated. It is only one tenth of a micron in size. in the still indoor air This droplet will not fall to the ground for several days.
Using the mask, some of the exhalation direction was changed down and significantly limited the forward movement of the feathers. Therefore, the risk of aerosols in the air is greatly reduced.
“To simplify the breathing process We did not consider the flow of airborne saliva mixture through the nose and only the flow through the mouth,” Khosronejad said. We will study the effect of normal breathing through the nose and mouth.”
Humid air can prolong the lifespan of virus-infected aerosols.
Ali Khosronejad et al, Computational study of respiration particle transport and vortex changes during respiration with and without mask. Fluid Physics (2021). doi: 10.1063/5.0054204
Provided by the American Institute of Physics
reference: Normal breathing sends 7 feet of saliva; Shorter Mask (2021, June 9) Retrieved June 9, 2021 from https://phys.org/news/2021-06-saliva-droplets-feet-masks-shorten.html.
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