MUST READ! Social Distancing: Study Shows Six Feet Insufficient To Prevent SARS-CoV-2 Transmission In A Light Breeze
: Airborne transmission of pathogens, like the SARS-CoV02 corona virus causing COVID-19, is not well understood, but a good baseline for research is a deeper understanding of how particles travel through the air when people cough.
A new research paper published in journal Physics of Fluids by Talib Dbouk and Dimitris Drikakis from the University of Nicosia demonstrate that with even a slight breeze of 4 kph, saliva droplets travels 18 feet in 5 seconds. https://aip.scitation.org/doi/10.1063/5.0011960
Saliva droplets can travel large distances, depending on environmental conditions such as wind speed,
temperature, pressure and humidity. Wind shown blowing left to right at speeds of 4 kph (top) and 15 kph
(bottom) can transport saliva droplets up to 6 meters (18 feet). Credit: Image courtesy of the authors
Drikakis told Thailand Medical News, “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.”
Typically, saliva is a complex fluid, and it travels suspended in a bulk of surrounding air released by a cough.
Numerous factors affect how saliva droplets travel, including the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, how heat and mass are transferred, and the humidity and temperature of the surrounding air.
In order to study how saliva moves through air, Dbouk and Drikakis created a computational fluid dynamics simulation that examines the state of every saliva droplet moving through the air in front of a coughing person. Their simulation considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapor and evaporate.
It should be noted that the computational domain in the simulation is a grid representing the space in front of a coughing person. The analysis involved running partial differential equations on 1,008 saliva droplets and solving approximately 3.7 million equations in total.
Dbouk said, “Each cell holds information about variables like pressure, fluid velocity, temperature, droplet mass, droplet position, etc. The purpose of the mathematical modeling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the saliva droplets themselves.”
Additional studies are needed to determine the effect of ground surface temperature on the behavior of saliva in air and to examine indoor environments, where air conditioning significantly affects the particle movement through air.
Drikakis further added, “This work is vital, because it concerns the health and safety of social distancing guidelines and also advances the understanding of spreading and transmission of airborne diseases, and helps form precautionar
y measures based on scientific results.”
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