In collaboration with TU/e
The video shows a 3D flow simulation with dispersion of large droplets and also aerosols or micro-droplets, due to breathing, coughing and sneezing by two opposing persons. Aerosols consists of a cloud of large (> 5-10 µm) and small fine droplets (<5 µm) and droplet cores.
Situations have been simulated in which two people are directly opposite each other at 0.5m, 1.0m and 1.5m distance. The drops are ejected from one person’s mouth towards the person opposite. A transparent Face Shield, worn by one of the two persons, is the only barrier. The Face Shield is completely closed at the top of the forehead with a foam tape that forms to the forehead.
Each simulation shows the effect of droplet dispersion due to one person ejection, at a speed of 2.5 m/s in case of breathing, 10 m/s in case of coughing and 50 m/s in case of sneezing. A distinction is made in droplet sizes ranging from 1 μm to 400 μm, with the smallest drops colored blue and the largest drops red. In case of contamination with SARS-CoV19, a large diameter droplet may contain more virus. The Face Shield is primarily intended to protect us against these droplets containing viruses, as these are expected to present the greatest risk of infection.
In case the person wearing the Face Shield breathes, coughs or sneezes, it’s clearly visible that the majority of the droplets, especially the large droplets, touch the inside of the mask and are stopped there. Only the smallest droplets can deposit on the body through the open bottom of the mask. This can prevent direct infection of the other person.
In case the opposite person breathes, it can be seen that the large droplets fall on the ground because of gravity before they can reach the other person. In case of coughing and sneezing, where the speed is higher, the droplets are stopped by the Face Shield.
NB: Evaporation is not included in this simulation. It’s likely that the small particles largely evaporate at distances greater than 0.5m and before they will deposit on the body, and then travel on as solid cores.