THESIS
2020
xix, 133 pages : illustrations ; 30 cm
Abstract
Bioaerosol deposition, distribution, and detachment behavior on near surfaces from a
cough is important for risk assessment and control of the contact route of respiratory disease
transmission, such as SARS, H1N1, seasonal influenza, and Covid-19. A custom-built cough
generator was used to simulate a real cough. Escherichia coli (E-coli) and bacteriophage were used
to represent the common respiratory bacteria and viruses, respectively. Firstly, bioaerosol
deposition and distribution on front flat surfaces were studied. The cough jet impinges on the front
surface and then forms a parallel spreading flow above the surface. The distributions of viable
bacteria/viruses follow the skew normal equation. Survivability of bacterium/virus during the
cough and deposition processes is almo...[
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Bioaerosol deposition, distribution, and detachment behavior on near surfaces from a
cough is important for risk assessment and control of the contact route of respiratory disease
transmission, such as SARS, H1N1, seasonal influenza, and Covid-19. A custom-built cough
generator was used to simulate a real cough. Escherichia coli (E-coli) and bacteriophage were used
to represent the common respiratory bacteria and viruses, respectively. Firstly, bioaerosol
deposition and distribution on front flat surfaces were studied. The cough jet impinges on the front
surface and then forms a parallel spreading flow above the surface. The distributions of viable
bacteria/viruses follow the skew normal equation. Survivability of bacterium/virus during the
cough and deposition processes is almost uniform on near surfaces. Secondly, bioaerosol
deposition and distribution on nearby seats in a cabin environment were studied, which is a
common enclosed environment to cause respiratory disease transmission. The viable virus on front
seat is one order of magnitude higher than that on the other near seats because of the large droplets
on front seat. Increasing the height of the backrests or opening the air jet for the infector could
reduce the virus deposited on front seat to less than 10%. Thirdly, the detachment behavior of
deposited droplets from a solid surface was studied. The droplet detaches totally from a surface
under a lateral force, while it detaches partially under a normal force, leaving a smaller droplet on
surface. The adhesion of a droplet to a rough surface depends on the liquid film left on surface
after droplet detachment. The surface energy analysis integrating the left liquid film has a good
linear relationship with the experimental adhesion. The bioaerosol deposition, distribution, and
detachment dynamics on near surfaces from a cough help understand the contact route and setup
the engineering control of respiratory disease transmission.
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