The new study looks at how airflow patterns inside the car’s passenger cabin affect the transition to SARS-Cavi-2 and other aerobic pathogens. Using computer simulation, the study looked at the risk of splitting aerosol particles between the driver and the passenger in different configurations of the window. Redder shades indicate more particles. Dangers were shown higher with windows closed (top left), and decreasing with each window opening. In the best case all the windows were open (bottom right). Credit: Brear Lab / Brown University
In a new study, computer simulations are used to track the flow inside the car’s passenger cabin to reduce the risk of transmission of vehicle diseases, providing a possible strategy.
A new study of airflow patterns inside car passenger cabins offers some risk mitigation tips COVID-19 Transmission while sharing rides with others.
The study, conducted by a team of researchers at Brown University, used computer models to simulate airflow inside a compact car with various combinations of windows open or closed. These simulations showed that open windows – the more windows the better – created an airflow pattern that dramatically reduced the concentration of airborne particles changing between the driver and the same passenger. Researchers have found that the car’s ventilation system does not allow air to circulate in the blast, as well as in a few open windows.
Asimanshu Das, a graduate student at Brown’s School of Engineering and co-lead author of the research, said, “Driving on Windows and keeping the air conditioning or heat on is definitely the worst situation,” The author, Asimanshu Das said. “The best scenario we saw was to have all four windows open, but keeping one or two open was better than keeping them all closed.”
Das did the research with participant Verghese Mathai, a former postdoctoral researcher at Brown, who is now an assistant professor of physics at the University of Massachusetts, Amherst. The study is published in the journal Science progress.
A study recently published in Science Advances looks at how airflow patterns inside a car’s passenger cabin affect the transition to SARS-Cavi-2 and other airborne pathogens. These simulations produced some possible reactive findings. For example, one might expect that opening windows directly next to each business might be the easiest way to reduce exposure. Simulations have found configuration that this configuration is better than down windows, it has a higher exposure risk than placing a window against each occupant. “When the windows in front of the occupants are open, you get a stream that enters the driver’s back of the car, turns to the passenger’s rear cabin, and then exits the passenger side window,” said Kenny Brewer, a professor of engineering. Said Brewer. Brown and senior author of the research. “That pattern helps reduce cross contamination between the driver and the passenger.” Credit: Brear Lab / Brown University
Researchers emphasize that there is no way to completely eliminate the risk – and, of course, the US Centers for Disease Control (CDC) has noted that postponing travel and staying home is the best way to protect the health of individuals and communities. The goal of the study was to simply study how changes in air flow inside a car can impair or reduce the risk of pathogenic transmission.
The computer models used in the study determined the car, loosely based on the Toyota Prius, with two people inside – the driver and the passengers in the back seat sitting opposite the driver. The researchers chose that seating arrangement because it maximizes the physical distance between two people (although it is less than the 6 feet recommended by the CDC). The models mimic the airflow around and inside a car moving at speeds of up to 50 miles per hour, as well as the movement and concentration of aerosols coming from both the driver and the passenger. Aerosols are small particles that stay in the air for a long time. They are considered a way in which SARS-CoV-2 The virus spreads, especially in enclosed spaces.
One of the reasons why it is better to open the windows in terms of aerosol transmission is because it increases the number of air changes in hours (ACH) inside the car, which helps reduce the overall concentration of aerosols. But HH was only part of the story, the researchers say. Studies have shown that different combinations of open windows create different air currents inside the car that can increase or decrease exposure to the remaining aerosols.
Due to the air flow in the outside of the car, the air pressure near the rear windows is higher than the pressure of the front windows. As a result, air enters the car through the rear windows and exits through the front windows. With all the windows open, this tendency creates two-more-less independent currents on either side of the cabin. The occupants in the simulations sat on opposite sides of the cabin, so very few particles are transferred between the two. This scenario carries a slightly higher risk to the driver than the passenger as the average airflow in the car moves backwards and forwards, but both vehicle transactions experience dramatically less transfer of particles than in other scenes.
Simulations for scenarios in which some but not all windows are down have some possible counterpart results obtained. For example, one might expect that opening windows directly next to each business might be the easiest way to reduce exposure. Simulations have found configuration that this configuration is better than down windows, it has a higher exposure risk than placing a window against each occupant.
“When the windows in front of occupants are open, you get a stream that enters the driver’s back of the car, turns to the passenger’s rear cabin, and then the passenger goes out the side front window,” said Kenny Brewer, a professor of engineering. Said Brewer. Brown and senior author of the research. “That pattern helps reduce cross contamination between the driver and the passenger.”
Researchers say it is important to note that there is no option to adjust the airflow to wear a mask by both rides while inside the car. And the findings are limited to the potential exposure to delayed aerosols that may contain pathogens. This study did not model the risk of infection with large amounts of respiratory drops or viruses.
Still, researchers say the study provides valuable new insights into the pattern of air circulation in a car’s passenger compartment – something that had received little attention before now.
“This is the first study we’ve been aware of that actually looked at the microclimate inside a car,” Brewer said. “There were some studies that looked at how much external pollution comes into the car, or how long the cigarette smoke stays in the car. But this is the first time anyone has paid detailed attention to the airflow pattern. ”
The research came from the COVID-19 research task force set up at Brown to gather expertise from the university to consider a wide variety of aspects of the epidemic. The group is led by Jeffrey Bailey, associate professor of pathology and laboratory medicine and co-founder of airflow studies. Impressed with how quickly Bailey came up with the research, Mathai suggested the use of a computer simulation that could be done when he paused for laboratory research epidemic at Brown.
“This is truly an example of how different branches can come together quickly and produce valuable findings,” Bailey said. “It’s one of the great things about living in a place like Brown, where people are eager to collaborate and work in branches.”
References: Varghese Mathai, Asimanshu Das, Jeffrey A. By Bailey and Kenneth Beuer, 4 December 2020, “Instructions for airflow and airborne disease transmission inside passenger trains”. Science progress.
DII: 10.1126 / sciadv.abe0166
