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What Windows You Should Open to Minimize C-19 Risk

University researchers used CFD to determine how to reduce possible contamination between driver and passenger


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“What is the transport of air and potentially infectious aerosol droplets between the driver and the passenger, and how does that air exchange change for various combinations of fully open and closed windows?”

That is the question that was asked by university researchers (Varghese Mathai of University of Massachusetts and Brown University; and Asimanshu Das, Jeffrey A. Bailey and Kenneth Breuer all of Brown), one that is important nowadays given the coronavirus pandemic and the fact that people are going to drive.

So the researchers ran a series of computational fluid dynamics (CFD) simulations in a four-door modeled on a Toyota Prius. They put the driver in the front left seat and a passenger in the rear right, thereby putting the greatest amount of distance possible between the two. Not exactly the CDC’s recommended six feet, but close.

Then it was a matter of determining the best arrangement of the four side windows (up or down) in a vehicle traveling at 50 mph as regards the air change rate (ACH) in the cabin.

You Could Open All of Them. . .

Not surprisingly, all windows open has the highest ACH, 250. And all windows closed the lowest: 62.

But what is surprising is what was found when the windows next to the driver (front left) and passenger (rear right) were opened.

As the researchers report, the metric is “only 89—barely higher than the all-windows-closed configuration.”

Short of having all four windows open, the best arrangement is for the windows opposite the driver and the passenger to be open (front right, left rear) to be open.

Kenneth Breuer, professor of engineering at Brown, told ScienceDaily, “When the windows opposite the occupants are open, you get a flow that enters the car behind the driver, sweeps across the cabin behind the passenger and then goes out the passenger-side front window. That pattern helps to reduce cross-contamination between the driver and passenger.”

It is worth noting that the researchers point out that it is still essential for the occupants to wear masks.

What’s more, they point out in their paper, “Preliminary models indicate a build-up of the viral load inside a car cabin for drives as short as 15 min, with evidence of virus viability within aerosols of up to 3 hours.”

CFD interior diagram

Airflow within a vehicle modeled by CFD by university researchers determining the best windows to be opened to minimize cross-contamination between the driver and rear-seated passenger. (Image: https://advances.sciencemag.org/content/early/2020/11/30/sciadv.abe0166 )


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