RhinoCFD - Spread of germs due to a sneeze visualized

In the age of social distancing, there is a lot of debate over what the ideal distance should be. In the context of COVID-19, airborne transmission may be possible in specific circumstances and settings in which procedures or support treatments that generate aerosols are performed [1]. This then implies that the simple act of breathing, coughing or sneezing could lead to the spread of infectious virus particles.

Sneezes in particular are violent events and are prime methods for spreading infections via airborne particles. A single sneeze averages over 100km/h for about half a second, and releases a cloud of particles of different sizes. Usually, we attempt to cover our mouths with a tissue or our elbow, but sometimes this doesn't happen. Thus, this has been taken as a worst-case scenario from a modelling perspective to see the effects this type of action could have on a person in a normal environment.
This simulation shows the consequences of an unmitigated sneeze and models two different particle sizes, 400 microns and 70 microns, which encompass the majority of the particles expelled in a sneeze. The model itself makes use of RhinoCFD and PHOENICS’ aerosol deposition model, which allows concentrations of particles to be modelled implicitly rather than explicitly thus making the simulation much more economical while retaining the ability to allow them to “slip” under their own weight with respect to the air that carries them.

The isosurfaces plotted represent areas with a concentration of 1% with respect to the amount of particles exiting the person’s mouth .As we can see, the larger particles, which would likely contain a higher viral load, lose momentum rather quickly and soon drop to the floor, limiting the range of their spread.

Smaller particles however, are carried further with the force of the sneeze, so although they are likely to contain fewer viral strands, they are likely to reach further away from the initial subject.

Further research might be necessary to determine the effect of covering one’s mouth, either by sneezing into one’s elbow, hand or a mask and comparing the spread to this unmitigated case.