Imagine a cloud of gas launching from your nose and mouth when you sneeze or cough. According to new research, this is exactly what happens, allowing particles from sneezes and coughs to travel up to 200 times farther than previously thought.
The study by Massachusetts Institute of Technology showed that the droplets produced when we cough or sneeze are accompanied by “gas clouds” that enable them to traverse greater distances. As a result, coughs and sneezes are far more capable of spreading viruses than scientists had thought.
“When you cough or sneeze, you see the droplets, or feel them if someone sneezes on you,” study co-author Dr. John Bush, a professor of applied mathematics at MIT, said in a statement. “But you don’t see the cloud, the invisible gas phase. The influence of this gas cloud is to extend the range of the individual droplets, particularly the small ones.”
Bush described a cough or sneeze as a “multiphase turbulent buoyant cloud,” because the cloud mixes with surrounding air before the liquid droplets fall out, evaporates into solid residue or both. The study was recently published in the Journal of Fluid Mechanics.
For the experiment, researchers used a combination of high-speed imaging, mathematical modeling and laboratory simulations, which allowed them to analyze the fluid mechanisms behind coughs and sneezes. Contrary to previous belief, each mucus droplet from a cough or sneeze is connected through interaction with a gas cloud. While previous research suggested that larger drops travel farther than smaller drops because they have more strength behind them, the MIT investigators found that when droplets merge with the gas cloud, their trajectories are altered.
Droplets that are 10 micrometers in diameter were found to travel 200 times farther than past estimates, while droplets 100 micrometers in diameter traveled five times farther. (more…)