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Track the trajectories of the evaporating cough drops



Circulatory flow Ho

Circulatory currents, namely awakened, are observed both in front of the couch (left) and in the back of the listener (right). A drop can be caught up in and trapped upon waking up, dramatically altering its trajectory and destiny. Credit: A * STAR Institute of High Performance Computing

Dispersion of large, medium, small cough droplets in the air under various outdoor conditions.

Happenning COVID-19 The pandemic has led many researchers to study the transmission of airborne droplets under different conditions and environments. The latest studies are beginning to incorporate important aspects of fluid physics to advance our understanding of viral transmission.

In a new article in Fluid physics, by AIP Publishers, researchers from A * STAR’s High Performance Computing Institute conducted a digital study of droplet dispersion using high fidelity gas flow simulations. The scientists found that a single 100-micrometer cough drop below a wind speed of 2 meters per second can fly as far as 6.6 meters and even further under dry air conditions due to the evaporation droplets.

Author Fong Yew Leong said: “In addition to wearing a mask, we found that distance from society in general is effective, as droplet deposition has been shown to alleviate a person at least 1 away from coughing. meters ”.

Researchers have used computational tools to solve complex mathematical formulas representing airflow and cough droplets in the air surrounding the human body at different wind speeds and when affected. by other environmental factors. They also evaluate deposition profiles on a person at a certain distance.

Droplet scattering

Droplet dispersion (side view, top view) from one cough to two people 1 m apart at (a) t = 0.52s, (b) t = 1s, (c) t = 3s and (d ) t = 5s. Credit: A * STAR Institute of High Performance Computing

A typical cough emits thousands of drops over a wide range of sizes. Scientists found that large drops of water settle to the ground quickly due to gravity but can be shone by up to 1 meter of coughing rays even in the absence of wind. Medium-sized droplets can evaporate into smaller, lighter, and more easily generated droplets by the wind, and these droplets fly further.

Researchers give a more detailed picture of droplet dispersion when they incorporate viral biological factors, such as the non-volatile content in the droplet evaporation, into the dispersion pattern in the air of the droplets.

“One drop of evaporated water keeps the virus’s content non-volatile, so the viral load is effectively increased,” said Hongying Li. “This means that the evaporated droplets become aerosols that are more easily inhaled deep into the lungs, causing infection down the respiratory tract than larger droplets that cannot evaporate.”

These findings are also highly dependent on environmental conditions, such as wind speed, humidity and ambient air temperature, and are based on assumptions made from existing scientific literature. about the viability of the COVID-19 virus.

While this study focuses on outdoor airborne transmission in tropical settings, scientists plan to apply their findings to risk assessment in indoor and outdoor environments. where crowds gather, such as halls or theaters. Research can also be used to design environments that optimize comfort and safety, such as hospital rooms that circulate indoor air and transmit germs in the air.

Reference: “The Dispersion of Volatile Cough Drops in the Outdoor Tropical Environment” by Hongying Li, Fong Yew Leong, George Xu, Zhengwei Ge, Chang Wei Kang and Keng Hui Lim, November 3, 2020, Fluid physics.
DOI: 10.1063 / 5.0026360




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