By the way, thanks again to all the people who gave me advice on alcohol-based markers a while back. I ended up buying the big, complete set of Marvy Le Plume markers, which I used to colour the Garden sisters. They’re cheap and they suit my purposes, though I could see myself filling out the set with some extra colours from other brands in the future. But for what they are, they’re a pleasure to use.
Sneezing and coughing are major contributors to the spread of many pathogens. Both are multiphase flows, consisting of both liquid droplets and gaseous vapors that interact. The image on the left shows a sneeze cloud as a turbulentplume. The kink in the cloud shows that plume is buoyant, which helps it remain aloft. The right image shows trajectories for some of the larger droplets ejected in a sneeze. Like the sneeze cloud, these droplets persist for significant distances. The buoyancy of the cloud also helps keep aloft some of the smaller pathogen-bearing droplets. Researchers are building models for these multiphase flows and their interactions to better predict and counter the spread of such airborne pathogens. For similar examples of fluid dynamics in public health, see what coughing looks like, how hospital toilets may spread pathogens, and how adjusting viscoelastic properties may counter these effects. (Image credit: L. Bourouiba et al.)