When You Cough, How Far Can The Coronavirus Go?
Dhir Acharya - May 25, 2020
To understand how far the coronavirus can go when someone coughs, we need to know how particles travel in the air. And a 2-meter distance is not enough.
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Many of us are still in the dark of virus transmission in the air, and a good way to understand this is knowing how particles travel in the air when someone coughs.
Dimitris Drikaris and Talbi Dbouk from the University of Nicosia in Cyprus conducted an experiment on this matter and found that even a light breeze at 4km/h and bring saliva droplets to as far as 6 meters in 5 seconds. A breeze at 15km/h can take particles that far in only 1.6 seconds. Drikakis says:
“The droplet cloud will affect both adults and children of different heights. Shorter adults and children could be at higher risk if they are located within the trajectory of the traveling saliva droplets.”
Saliva is a complex fluid that travels suspended with air released from a cough, according to the researchers.
Several factors affecting how saliva travels include the number and size of the droplets, how the droplets interact with the surrounding air and with each other when dispersing and evaporating, how mass and heat are transferred, as well as the temperature and humidity of the surrounding air.
To have a closer study about the movement of saliva, the two researchers generated a computational fluid dynamics simulation to examine the state of all saliva droplets that move through the air in front of a coughing person.
The factors taken into account are dispersion force, humidity, how the droplets turn into vapor and evaporate, and interactions of saliva molecules and air.
According to the researchers, in this simulation, the computational domain is a grid that represents the space in front of the coughing person. They ran partial differential equations with 1008 droplets and solved a total of 3.7 million equations.
In each cell, there is information on droplet position, droplet mass, temperature, fluid velocity, pressure, among other variables. The aim of modeling and simulation is to consider every real coupling and interaction mechanism that may happen between the saliva droplets and the main bulk fluid flow, as well as between the droplets.
The findings of this study point out a fact that social distancing with a 2-meter distance is simply not enough. That highlights the importance of self-quarantine and lockdowns during the COVID-19 pandemic.
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