Cough downwards to reduce spread of disease
Even as COVID-19 infections hit the 500-million mark, researchers continue to study the dispersion of respiratory droplets that contribute to the spread of the disease. According to a team from the American Institute of Physics (AIP), besides coughing or sneezing into your elbow, coughing downward can also reduce the spread of droplets as it keeps the bulk of droplets from propagating overhead, especially when moving up/down.
“Two different patterns of droplets dispersion are observed due to the different wake flows,” said AIP researcher Hongping Wang. “These results suggest that we should cough with the head down toward the ground to ensure that most of the droplets enter the wake region.”
The wake region is related to an interesting experiment conducted with mannequins. The AIP team 3D-printed mannequins using white resin, each with a different inclination angle to represent the leaning in that we subconsciously do when going up stairs and the leaning back when we walk down.
The mannequins and several hollow glass microspheres were placed in water tunnels, which, when illuminated by lasers, provided a way to visualise the flow motion of droplets. This flow field, often called a wake, was studied using a technique called particle image velocimetry.
In computer simulations, particles lower than the head and moving toward the ground became caught in each mannequin’s wake due to the induction of the wake flow. Conversely, particles dispersing above the head would move relatively far distances horizontally.
Wang and his team are curious to study the 3D effects of what happens in real-life situations, when people cough while walking in experimental conditions.
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