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Science

Open Windows May Reduce COVID-19 Risk In Cars: Study – Jalopnik

Published

2 hours ago

January 17, 2021

Harry Miller

Illustration for article titled Open Windows May Reduce COVID-19 Risk In Cars: Study — Photo: Dan Kitwood (Getty Images)

COVID-19 has completely changed the face of travel as we know it, with massively reduced numbers of people taking flights and public transportation—but our cars have remained a mystery. How safe are we in our vehicles? What are our risks?

A study published by Science Advances in early January has begun to answer some of our most pressing questions about COVID-19 transmission in our vehicles. Four scientists from the University of Massachusetts, Amherst and Brown University used computational fluid dynamics to evaluate the risks posed by the virus within a vehicle’s cabin and have also suggested ways to mitigate risk.

If you’re familiar with the design process of a race car or airplane, then you’ve likely encountered computational fluid dynamics before. Essentially, these computer simulations model how gases and liquids move over and through different surfaces. In this particular case, our scientists used CFD to model the way air moves inside a car.

The simulated vehicle used in the study was loosely based on a Toyota Prius traveling at 50 mph carrying two passengers: a driver in the front left of the car and a passenger in the back right. Interestingly, the air flow outside the moving car creates a pressure gradient inside the car that causes air to circulate from the back of the car to the front. Then, they started modeling the interior air flow with different combinations of the windows being open or closed. It’s important to note here that, no matter the combination, the air conditioning was on.

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The results probably aren’t going to be surprising. When all four windows were closed, the car was at its most poorly ventilated, so eight to 10 percent of aerosols—on which COVID-19 travels—exhaled by one person in the car traveled to the other. When all the windows were open, the car was at its best ventilated, with just 0.2 to two percent of aerosols swapping between passengers.

Of course, wide open windows aren’t always practical when you’re driving. Up north, you’ll freeze in the winter. Down south, someone with a delicate constitution will melt in the summer. A heavy rain will make things twice as miserable. So, having both the driver and the passenger roll down their windows was found to be better than keeping everything shut tight. That diagonal configuration allows air to flow in and then right back out. It might not be comfortable, but it could save lives.

A later study that hasn’t yet been published found that cracking windows halfway was also a good idea, but only rolling them a quarter of the way down was significantly more dangerous, the New York Times reports. For larger vehicles like minivans or for vehicles transporting more people, the recommendation is to keep everything open.

Opening windows has been recommended since the onset of the virus. The increased ventilation allows virus particles to be whisked away rather than recirculated. And we also know that the smaller the space we share, the more likely we are to swap aerosol particles. This study basically just used science to give us the ideal strategy for, say, rideshares or short jaunts outside your bubble.

Of course, there are still dangers, even when opening your windows. In fact, driving with your windows open increases in-car air pollution by 80 percent, which thus increases your likelihood of dying as a result of air pollution.

The very best option is, of course, to stay home unless absolutely necessary and, when traveling, to do so in off-peak hours.

Science

NASA's 8-Minute Rocket Test Shuts Down After 67 Seconds – KCCU

Published

5 hours ago

January 17, 2021

Harry Miller

NASA has more work to do, after a rocket test Saturday for its shuttle replacement ended with a premature and unexpected shutdown.

The test, at NASA’s Stennis Space Center in Mississippi, was part of NASA’s Artemis program, a plan to return to the moon in the coming years. NASA’s test called for four engines to fire for eight minutes — roughly the time it will take for NASA’s long-delayed Space Launch System (SLS) to generate the thrust needed to send the rocket to space.

But the engines shut down after just 67 seconds, when engine number 4 suffered a “major component failure.” Scientists aren’t yet sure what caused the early shutdown, but they plan to analyze and regroup.

Watch all four @NASA_SLS core stage engines roar to life and shake the ground in Mississippi.

Teams are assessing the data on early engine shutdown. pic.twitter.com/U5bNqqbdZd

— NASA (@NASA) January 16, 2021

“Saturday’s test was an important step forward to ensure that the core stage of the SLS rocket is ready for the Artemis I mission, and to carry crew on future missions,” said NASA Administrator Jim Bridenstine, who attended the test.

“Although the engines did not fire for the full duration, the team successfully worked through the countdown, ignited the engines, and gained valuable data to inform our path forward,” he said.

The engines NASA tested are the same ones that would be used to eventually launch the Orion space capsule to the moon. So scientists have to be careful with them.

“The amount of risk that we can take is very, very low,” Bridenstine said. “We can’t afford to have this vehicle fail. And guess what? Because we have done all the work that we have done, this article made the right decision to shut itself down.”

Well MCF was not a call this ascent flight director ever wanted to hear: Major Component Failure is detected by the SSME controller.

— Wayne Hale (@waynehale) January 16, 2021

Now NASA has to figure out what caused the component failure that led to the shutdown. If scientists conduct another test, it will take at least 3-4 weeks to prepare the engines, the agency said.

NASA announced the SLS about 10 years ago, as a successor to the retired Space Shuttle program. It’s a rocket and capsule combo that, when complete, will enable deep space missions. NASA hopes to have astronauts on the moon in 2024, and eventually Mars and beyond.

Science

How to literally drive the coronavirus away – Deccan Herald

Published

6 hours ago

January 17, 2021

Harry Miller

Over the past year, as health authorities have tried to curb the Covid-19 pandemic, researchers have trained their scientific attention on a variety of potentially risky environments: places where large groups of people gather and the novel coronavirus has ample opportunity to spread. They have swabbed surfaces on cruise ships, tracked case numbers in gyms, sampled ventilation units in hospitals, mapped seating arrangements in restaurants and modeled boarding procedures in airplanes.

They have paid less attention to another everyday environment: the car. A typical car, of course, does not carry nearly enough people to host a traditional superspreader event. But cars come with risks of their own; they are small, tightly sealed spaces that make social distancing impossible and trap the tiny, airborne particles, or aerosols, that can transmit the coronavirus.

“Even if you’re wearing a face covering, you still get tiny aerosols that are released every time you breathe,” said Varghese Mathai, a physicist at the University of Massachusetts, Amherst. “And if it’s a confined cabin, then you keep releasing these tiny particles, and they naturally would build up over time.”

Read: Decoding how airflow inside car may affect Covid-19 transmission risk

In a new study, Mathai and three colleagues at Brown University — Asimanshu Das, Jeffrey Bailey and Kenneth Breuer — used computer simulations to map how virus-laden airborne particles might flow through the inside of a car. Their results, published in early January in Science Advances, suggest that opening certain windows can create air currents that could help keep both riders and drivers safe from infectious diseases like Covid-19.

To conduct the study, the research team employed what are known as computational fluid dynamic simulations. Engineers commonly use these kinds of computer simulations, which model how gases or liquids move, to create race cars with lower drag, for instance, or airplanes with better lift.

The team simulated a car loosely based on a Toyota Prius driving at 50 mph with two occupants: a driver in the front left seat and a single passenger in the back right, a seating arrangement that is common in taxis and ride shares and that maximizes social distancing. In their initial analysis, the researchers found that the way the air flows around the outside of the moving car creates a pressure gradient inside the car, with the air pressure in the front slightly lower than the air pressure in the back. As a result, air circulating inside the cabin tends to flow from the back of the car to the front.

Next, they modeled the interior air flow — and the movement of simulated aerosols — when different combinations of windows were open or closed. (The air conditioning was on in all scenarios.) Unsurprisingly, they found that the ventilation rate was lowest when all four windows were closed. In this scenario, roughly 8% to 10% of aerosols exhaled by one of the car’s occupants could reach the other person, the simulation suggested. When all the windows were completely open, on the other hand, ventilation rates soared, and the influx of fresh air flushed many of the airborne particles out of the car; just 0.2% to 2% of the simulated aerosols traveled between driver and passenger.

The results jibe with public health guidelines that recommend opening windows to reduce the spread of the novel coronavirus in enclosed spaces. “It’s essentially bringing the outdoors inside, and we know that the risk outdoors is very low,” said Joseph Allen, a ventilation expert at the Harvard T.H. Chan School of Public Health. In an op-ed last year, he highlighted the danger that cars could pose for coronavirus transmission, and the potential benefits of opening the windows. “When you have that much turnover of air, the residence time, or how much time the aerosols stay inside the cabin, is very short,” Allen said

Because it is not always practical to have all the windows wide open, especially in the depths of winter, Mathai and his colleagues also modeled several other options. They found that while the most intuitive-seeming solution — having the driver and the passenger each roll down their own windows — was better than keeping all the windows closed, an even better strategy was to open the windows that are opposite each occupant. That configuration allows fresh air to flow in through the back left window and out through the front right window and helps create a barrier between the driver and the passenger.

“It’s like an air curtain,” Mathai said. “It flushes out all the air that’s released by the passenger, and it also creates a strong wind region in between the driver and the passenger.”

Richard Corsi, an air quality expert at Portland State University, praised the new study. “It’s pretty sophisticated, what they did,” he said, although he cautioned that changing the number of passengers in the car or the driving speed could affect the results.

Read | Consumers prioritising car ownership post-coronavirus lockdown, 74% want own vehicle: Survey

Corsi, a co-author of the op-ed with Allen last year, has since developed his own model of the inhalation of coronavirus aerosols in various situations. His results, which have not yet been published, suggest that a 20-minute car ride with someone who is emitting infectious coronavirus particles can be much riskier than sharing a classroom or a restaurant with that person for more than an hour.

“The focus has been on superspreader events” because they involve a lot of people, he said. “But I think what sometimes people miss is that superspreader events are started by somebody who’s infected who comes to that event, and we don’t speak often enough about where that person got infected.”

In a follow-up study, which has not yet been published, Mathai found that opening the windows halfway seemed to provide about the same benefit as opening them fully, while cracking them just one-quarter of the way open was less effective.

Mathai said that the general findings would most likely hold for many four-door, five-seat cars, not just the Prius. “For minivans and pickups, I would still say that opening all windows or opening at least two windows can be beneficial,” he said. “Beyond that, I would be extrapolating too much.”

Ride-sharing companies should be encouraging this research, Mathai said. He sent a copy of his study to Uber and Lyft, he said, but has not received a response.