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Davis

Davis, California

Tuesday, November 30, 2021

Column: Breaking wind

Everyone’s got a wind god. The Aztecs had Ehecatl, the Norse had Njord. The Greeks had Zephyrus, who fanned the city of Elysium with pleasant breezes. But we don’t need any wind gods in Davis.

We can make our own wind.

We have several man-made wind tunnels on the UC Davis campus. One is called the Saltation Wind Tunnel, and it’s used to test particle flow. Another is the Aeronautical Wind Tunnel. It tests airflow over objects like airplane wings.

The coolest wind tunnel in town, though, is the Atmospheric Boundary Layer Wind Tunnel (ABLWT) behind Bainer Hall.

The ABLWT sits in a room surrounded by tiny foam models of the world. There’s the UC Davis School of Veterinary Medicine complex and San Francisco Bay’s Treasure Island all made out of pink and blue foam. You can walk over to a scale model of San Francisco and tower over skyscrapers.

I felt like Godzilla.

Grey Taylor, an aeronautical and mechanical engineering major and wind tunnel technician at UC Davis, gave me a tour of the tunnel. He explained that the models are used to test for safe wind speeds. When a scale model is in the wind tunnel, a robot arm holds a tiny strip of wire over a specific location. An electrical current runs through the wire to make it hot, but when wind hits the wire, it cools down.

“We measure wind speed by measuring how much voltage [the wire] needs to stay at its temperature,” Taylor said.

Back in 2000, research at the ABLWT changed the San Francisco skyline. The builders of AT&T Park had UC Davis test wind speeds around the stadium. Tests showed that with the park facing south – the original plan – fans sitting near left field would have been hit by harsh wind. But if the field turned just 90 degrees, the fans would be happy. The builders changed the design with the recommendations of UC Davis, and the wind has been carrying home runs out of the stadium ever since.

Maybe Barry Bonds can thank UC Davis, not steroids.

“He should have contacted us if he wanted some help with his defense,” Taylor joked.

The ABLWT is 70 feet long with a huge fan that sucks up air from one side. When the air enters, it hits a honeycomb screen that breaks up eddies. The air then hits four vertical pillars that create turbulence. There are metal nuts along the floor of the tunnel which help slow down wind close to the ground. All these obstacles create a natural wind pattern called a boundary layer.

The boundary layer is the height where wind speeds get powerfully high and turbulent. Wind speeds get lower as you get closer to the ground. This dynamic is why winds on top of a mountain (or a hill in San Francisco) can be unbearable. When you put obstacles like metal nuts or buildings in the path of the wind, wind patterns closer to the ground change.

Alex Neigher, an atmospheric science major and member of The Aggie weather team, explained in an e-mail interview that extreme weather conditions often affect the boundary layer.

“Right before or after a big storm,” he said, “there is a lot of turbulence in the lower atmosphere. The turbulence can extend up to where the higher winds are in the atmosphere and mix these really high winds down to the surface where we interpret them as really high gusts.”

If you understand the boundary layer, the TV weather forecaster makes a lot more sense.

San Francisco is famously gusty, but high winds in Davis have also led to projects for the ABLWT. Taylor showed me a model of a building in the Vet Med center where high winds damaged an outward-facing door and risked employee injuries. Researchers at the ABLWT discovered that the funnel shape of the building combined with a second-story walkway created high winds on the ground level. The recommended solution: Plant a tree to block the wind.

With the search for alternative energy, wind turbines have become more popular. In September, San Francisco mayor Gavin Newsom revealed plans to install wind turbines on rooftops across the city. Wind is a renewable source of energy, so we mortals should strive to harness it.

Take that, wind gods.

MADELINE McCURRY-SCHMIDT blames all her bad hair days on the wind. E-mail her column ideas at memschmidt@ucdavis.edu.

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