| WMU News
KALAMAZOO, Mich.—Figuring out how the weather on Earth works is difficult enough. Now try deciphering atmospheric processes hundreds of millions of miles away on Jupiter, Saturn, Uranus and Neptune—the solar system's giant gas planets.
Shawn R. Brueshaber, a doctoral candidate at Western Michigan University, is trying to do just that, and his efforts earned him a NASA Earth and Space Science Fellowship. Brueshaber is one of only 28 applicants to be awarded a $30,000 award for 2016-17 from the fellowship's planetary science research division.
He's investigating polar vortices, large patches of air circulating near the pole. These circulations are sometimes bounded by a jet stream and tend to change shape over time, just as the Earth's polar vortex did in January 2014 when it plunged a broad area of Canada and the United States into a bitter deep freeze.
Profs provide extra support
Receiving the fellowship is a coup for the veteran engineer, who's taught thermodynamics, materials science and graduate-level fluid mechanics at WMU and earned a bachelor's degree in aerospace engineering from Embry-Riddle Aeronautical University and a master's degree in mechanical engineering from WMU.
During the past two decades, he's worked for several Michigan companies in a variety of roles—none of them related to weather or astronomy. But he's been fascinated by these subjects since childhood, and while gaining professional expertise in fluid mechanics, computational software and other traditional aspects of engineering, he kept studying and reading about them.
"I decided that after I finished the coursework for my Doctor of Philosophy in mechanical engineering, I wanted to study something of serious interest to me," he says. "My engineering background and self-study of weather and astronomy were good fits for a research topic using computational methods."
So, for his doctoral dissertation titled "Accumulation of Polar Vorticity in a Forced-Turbulence 3D Model," Brueshaber chose to investigate polar vortices on the solar system's gas planets. But it took extra support from his dissertation committee members to make such a project viable.
When he began work on his dissertation, WMU didn't have an academic department or program that focused on weather, climate or planetary studies. It also didn't have a related research lab or team that he could join. Undaunted, his doctoral committee chair, Dr. William Liou, worked with Brueshaber to meld his engineering skills with his personal interests.
Liou and fellow committee member Dr. Tianshu Liu, both professors of mechanical and aerospace engineering at WMU, also happened to know working planetary science and atmosphere researchers at other universities. In fact, Liu introduced Brueshaber to Dr. Kunio Sayanagi, assistant professor of atmospheric and planetary sciences at Hampton University, who's now on his doctoral committee and works closely with him on his research.
"The motion of fluids ranging from the very small to the very large—like an atmosphere—is governed by physical laws and fairly well understood. But the turbulent nature of fluids is the last remaining branch of classical physics that still defies a complete understanding," Brueshaber says. "WMU's mechanical and aerospace department understood that there was a nice connection between computational methods and weather if we could find the right folks to help out, and we did. I give a lot of credit to Drs. Liou and Liu for being willing to help in this endeavor, and to Dr. Sayanagi."
Enigmas still stymie scientists
Armed with his NASA fellowship funding, Brueshaber is continuing to delve into what influences a polar vortex. He notes that the research fits with NASA's interest in expanding both basic and applied science about atmospheric phenomena on Earth and all other planets.
Brueshaber says polar vortices are seen on Earth, Mars and Venus, our terrestrial worlds, as well as Saturn's moon Titan, which is the only moon in the solar system with a thick atmosphere. Except for Venus, they're seasonal features that come in the fall and winter and disappear in the spring. Polar vortices are harder to understand on Jupiter, Saturn, Uranus and Neptune, which he says are really just big balls of fluids.
"Turbulence is one of those problems in physics, engineering and meteorology that doesn't have a comprehensive theory yet. We can make some remarkable and accurate predictions of atmospheric motion and fluid motion in engineering devices such as pumps, airplane wings and heat exchangers, but we're still a bit in the dark on a comprehensive understanding," Brueshaber says. "Turbulence plays very much into the mechanisms behind the formation of vortices, storms and jet streams. By studying the giant planets, we learn about weather and climate without a lot of complicating factors. There are no mountains, no oceans, no land or ice caps. In some ways, they're simpler than our world."
Still, Brueshaber says, that doesn't mean gas planets are well understood. For instance, scientists learned this past summer that Jupiter doesn't have a polar vortex at all. Saturn, on the other hand, has a vortex at both the north and south poles but unlike any others known to date, these vortices remain even when the seasons change. Meanwhile, Neptune has a vortex at its south pole, but it changes shape for unknown reasons.
Simulations delve into differences
To figure out what's causing such differences, Brueshaber is using numerical simulations that take into account key variables. By modeling their effect, he hopes to gain a better understanding of the fluid-dynamic characteristics of polar vortices and determine which variables favor and suppress vortices.
"I have a hypothesis of why these storms exist, and my work to date shows similar results to a previous researcher who predicted that Jupiter wouldn't have a polar vortex," he says.
Brueshaber is doing a preliminary set of computational experiments that examines the influence of a planet's size and rotational speed, strength of small-scale storms, and spin direction of small-scale storms. Do these variables favor emergence of a polar vortex and if so, how big and strong is the vortex?
He'll start the next phase of his work this spring, when he looks at how the temperature at different depths of an atmosphere affect any polar vortex.
"If we can close the gaps of our understanding of turbulence in general, we may not only increase our predictive power of Earth's climate and weather, we might even make some breakthroughs that could help us design better fluid mechanic devices and help develop fusion power," he says. "Fusion powers the sun and is a wonderfully green energy source. Right now, turbulence in the fusing plasma is preventing us from keeping a sustained reaction from occurring for more than a second or so."
Brueshaber says he eventually wants knowledge of weather and climate to span additional worlds.
"We're on the threshold of starting to study climate on a number of the newly discovered planets in other solar systems," he says, "so we're going to learn even more, and the mysteries will deepen."
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