Face shields no match for sneeze vortex rings
Face shields worn alone are not effective against COVID-19 sneezes

Date:
December 8, 2020
Source:
American Institute of Physics
Summary:
Do face shields provide enough protection to the wearers against
COVID-19 if they don't also wear a mask? No. But researchers in
Japan are working to create face shields safe enough to be worn
alone. In a new article, the researchers describe their work to
gain a better understanding of what happens to the airflow around
a face shield when someone nearby sneezes.



FULL STORY ==========================================================================
Do face shields provide enough protection to the wearers against COVID-19
if they don't also wear a mask? Spoiler alert: no. But researchers at
Fukuoka University in Japan are working to create face shields safe
enough to be worn alone.


==========================================================================
The researchers originally set out to explore whether surgical masks and
face shields used as preventive measures are effective, as well as to
determine if the stress of wearing a N95 surgical mask for long periods
could be reduced.

In Physics of Fluids, from AIP Publishing, Fujio Akagi and colleagues
describe their work to gain a better understanding of what happens to
the airflow around a face shield when someone nearby sneezes. Sneezes are intriguing, because they produce a fluid phenomenon known as vortex rings.

"A vortex ring is a donut-shaped vortex that is generated by
an instantaneous ejection of fluid from a circular orifice," said
Akagi. "This resembles bubble rings made by dolphins." These vortex rings
can capture microscopic particles, which sneezing also generates. What
happens when a face shield wearer is exposed to a sneeze from an infected person standing 1 meter (39.3 inches) in front of them? "The vortex
rings generated by the sneeze capture the microscopic droplets within
the sneeze and transport them to the top and bottom edges of the face
shield," said Akagi, adding that droplets travel to the face shield
wearer quickly -- within 0.5 to 1 second after the start of the sneeze.



==========================================================================
"If this arrival time is synchronized with inhalation, the shield wearer
will inhale the droplets," Akagi said.

The researchers made three findings everyone should know: First, droplets
of sneezes are transported not only by the high velocity airflow caused
by sneezing, but also by the vortex rings generated by sneezing.

Second, microscopic droplets transported by these vortex rings can get
inside the shield through its top and bottom edges.

Third, face shields alone are not highly effective to prevent COVID-19 infection.

By gaining a better understanding of face shield weaknesses, researchers believe the protection can be enhanced by reducing the flow getting
inside the shield.

"We are currently developing and demonstrating several improved shields,"
said Akagi. "We want to contribute to keeping people safe from infection,
and believe that one day in the near future, medical workers will be
able to prevent infection using only a face shield and a regular mask or, ideally, with only a face shield."

========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Fujio Akagi, Isao Haraga, Shin-ichi Inage, Kozaburo Akiyoshi. Effect
of
sneezing on the flow around a face shield. Physics of Fluids,
2020; 32 (12): 127105 DOI: 10.1063/5.0031150 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201208111442.htm

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