WIND ADVISORY: Experts say windy weather increases spread of COVID-19

By Mark Waghorn via SWNS

Windy weather speeds up the spread of COVID-19, according to new research.

Gusts blowing in the same direction as a cough increases the transmission of the virus.

People should wear masks outside — especially if it's breezy, say scientists.

Co-author Professor Amit Agrawal, of the Indian Institute of Technology Bombay, said: "The study is significant in that it points to the increased infection risk that coughing in the same direction as the wind could bring about.

"Based on the results, we recommend wearing masks outdoors, particularly in breezy conditions."

Other guidelines, such as coughing in an elbow or turning the face away, should also be followed when socializing in the open air.

The analysis found even a light breeze of about 5 mph extends effective social distancing by around a fifth.

Depending on cough strength it lengthens from three to six feet to 3.6 to 7.2 feet.

At 9 to 11 mph, the spreading of COVID-19 increases in distance and duration.

Most studies model cough flow using puffs of air or a simple pulsating profile.

But a real cough is more complicated, exhibiting turbulent flow with prominent vortical structures swirling like mini whirlpools.

So the researchers used a large eddy simulation, a computational fluid dynamics technique that models turbulence.

They investigated cough jets in breezy and calm conditions representing a typical indoor environment.

The vortices enabled bigger droplets to persist in the air longer than has been typically assumed.

This increased the time it takes to adequately dilute the viral load in fresh air.

As the cough jet evolves and spreads, it interacts with the wind flowing in the same direction.

The bigger infected droplets become trapped in the jet's vortices instead of falling relatively quickly to the ground under gravity.

Prof Agrawal said: "The increase in residential time of some of the larger droplets will increase the viral load transmitting through the cough jet and, therefore, the chances of infection."

He added: "Overall, the study highlights increased chances of infection in the presence of even a light breeze."

The study is in Physics of Fluids.