The drops produced from the cough of an individual King spread differently in a narrow corridor and open space. In a narrow corridor, the dot is concentrated in small bubbles and left behind. Credit: Xiaoli Yang
A brisk walk in a narrow corridor can increase COVID-19 Transmission risk.
Long streams of virus-filled drops can set foot behind infected individuals walking through narrow corridors, affecting safe social distance guidelines.
Computational simulations are used to accurately predict AOVflow and Drupalt dispersal methods where COVID-19 spreads. In the journal The physics of fluids, By AIP Publishing, the results show the importance of space shaping in modeling how a virus-filled dot moves through the air.
Similarities are used to determine the pattern of rear flow of a walking King person in different shaped spaces. The results reveal a high transmission risk for children in some cases, such as behind people moving fast in long narrow corridors.
Previous investigations using this simulation technique have helped scientists understand the effects of objects on glass barriers, windows, air conditioners and toilets, as well as air flow patterns and the spread of viruses. Previous simulations typically take up large, open indoor space but do not take into account the effect of nearby walls, such as those existing in a narrow corridor.
The drops produced from the cough of an individual King spread differently in a narrow corridor and open space. In the open space, the drops spread over a wide range connected to the person. Credit: Xiaoli Yang
If a person walking in a corridor coughs, his or her breath drops out of the calcine that travels around and behind their body, awakening in the water the way a boat travels. Investigations have revealed the existence of a “re-circulation bubble” flowing directly behind the person’s torso and again behind them at waist height.
“The patterns of flow we have found are strongly related to the shape of the human body,” said author Xiaoli Yang. “At 2 meters downstream, Wake’s mouth height and leg height are almost negligible, but he still appears at waist height.”
Once the airflow pattern was determined, the probe was modeled to disperse a cloud of dot driven from the mouth of a simulated person. The shape of the space around a moving person is especially crucial for this part of the calculation.
Two types of scattering conditions were found. In one position, the cloud of drops separates from the moving person and floats behind the person, creating a floating bubble of drops filled with the virus. In the second mode, the cloud is attached to the person’s back, moving backwards from space like a tail behind them.
In both cases, the cloud of drops moves at about half the height of the infected person before reaching the ground, which puts children at greater risk of drip breathing. Credit: Xiaoli Yang
“For the detached mode, the concentration of drops is much higher than the connected mode, five seconds after coughing,” Yang said. “Determining safe social distances in places like these very narrow corridors poses a big challenge. Where a patient can inhale viral drops even if a patient is in front of him or her.”
This risk is especially great for children, because in both cases, a cloud of droplets moves above the ground at half the height of the infected person – in other words, at the mouth level for children.
Reference: By Xiaobin Li, Hongping Wang, Xinle Zheng, Ting Wu and Xiaolei Yang, 15 December 2020, “The effect of space size on the diffusion of drops produced by coughing from a walking person” The physics of fluids.
DOI: 10.1063 / 5.0034874
