The violent churning of river water as currents of different speeds collide over rapids. The dull thrum of air buffeting the window of a moving car. The sudden change in color when cream is stirred into coffee. The energy of these events results from the interplay of fluids with an object on the move. At the heart of each is a process called turbulence that has held the attention of Professor Bob Moser for some 30-plus years, with no java jolt required to boost his enthusiasm.
“It just amazes me that with something as simple as stirring coffee, turbulence works its magic,” says Moser, the deputy director of ICES. “You pour milk into black coffee, and maybe you see a drop of white in the middle. Then you put a spoon in for a couple of strokes and ‘boom!’ Suddenly, it’s cream colored. That’s because turbulence is so effective.”
Moser’s scientific passion is developing the analytical tools to understand turbulence, which is necessary for efficient combustion inside engines, eases the flight of golf balls and helps keep airplanes aloft. But the intricate physical interactions of turbulence have a dark side, from increasing drag on moving vehicles, to transferring the heat that scorches space vehicles re-entering the Earth’s atmosphere. To help curtail these downsides and increase the pluses, Moser has mastered the creation of numerical simulations that capture turbulence in ever-increasing detail. “In research, the devil is in the details, and we’re all about the details,” says Moser, who is the W. A. “Tex” Moncrief Jr. Chair in Computational Engineering and Sciences and professor of mechanical engineering in thermal fluid systems.
He repaired bicycles and lawnmowers as a teen, and taught himself Newtonian physics in high school. By the time Moser was pursuing a master’s degree at Stanford University, he was using his knowledge of mechanical engineering and physics as a prestigious NASA-funded fellow on computational dynamics. “You could tell Bob was very sharp right from the beginning,” says Parviz Moin, the mechanical engineering professor who became Moser’s doctoral advisor at Stanford. “He was probably the best of that fellowship group,” he adds, recalling a mistake that Moser caught on a blackboard while taking one of his math classes.
It quickly became clear that Moser’s capabilities extended to research. When his career began, turbulence experiments in wind tunnels ruled the day. While completing his doctoral degree, his mastery of numerical methods and insight into computer architecture allowed him to conduct the first study that demonstrated direct numerical simulations of wall-bounded turbulent flow, which was published in 1987 in his field's most prestigious journal. “That opened up a brand new area of research using supercomputers to study turbulent flows, which is probably the most important area now in the field,” Moin notes.
His research in turbulence continued, leading in 1999 to his publication of a simulation of turbulence in a fully developed channel flow, which added 2,000 citations to his 12,000-plus total. This was the first in a series of simulations performed in Moser's group with ever more detailed turbulent flow features. The data they produced were among the earliest of this type provided on the web for researchers globally. His colleague, Nagi Mansour, who worked with Moser at NASA’s Ames Research Center soon after he graduated from Stanford, noted his commitment to scientific advances in general. “Not only did he move the entire field of wall-bounded flow turbulence to the next level, he also introduced NASA colleagues like me to new computing technologies,” says Mansour, now the chief of the computational physics branch at Ames.
Moser remains at the creative forefront of studying direct numerical simulations, including large-scale simulations of wall-bounded flow and other phenomena requiring massively parallel computations. Along the way, his emphasis on improving the simulations has helped them represent turbulence affecting everything from autos to airplanes with 29 times more detailed flow features, allowing for more realistic representations.
He is also known for thoughtful leadership within the American Physical Society (APS), as a journal and program reviewer, and in coordinating national and international workshops. Moser’s research accolades include the NASA Medal for Scientific Achievement for contributing to the understanding of turbulent wakes and mixing layers with the potential to improve the efficiency of combustors and multi-element airfoils. He was also named an APS fellow for achievements that include his insightful, elegant analysis of the 3-D structure of turbulence.
Moser’s leadership credits include starting the Center for Predictive Engineering & Computations Sciences (PECOS) in 2008, just a few years after joining ICES. “His success at running that center helped put UT at the forefront of computational sciences,” Moin says. To honor Moser for his 60th birthday and accomplishments, ICES will hold a symposium August 16.
If you ask Moser about his contributions, the work of others comes up, such as on the Department of Energy grant that he garnered to help start PECOS. The grant addressed ways to improve computational predictions of turbulence-related heating experienced by NASA’s re-entry vehicles. “I’m proud that one of my team, over a couple of years, spent many months as a computational scientist with NASA’s experimental team really improving the reliability of their measurements,” Moser says of Dr. Marco Panesi, now a faculty member in his own right.
Colleagues note that that tendency to focus on others is par for the course. Mansour recalls of working beside Moser at NASA in the 1980s and 1990s, “He really mentored a lot of young scientists and would do that very generously.” Moin agrees. “He has a sharp mind and wit, and is a giving professional,” he says.
Moser’s leadership roles began at his first faculty position at the University of Illinois at Urbana, Champaign. His service activities there included chairing the engineering college’s executive committee and serving as interim head of the theoretical and applied mechanics department. “If people think I can contribute, I try to do that,” he says, often putting in long hours as ICES’ deputy director.
In addition to participating in many ICES committees nowadays, he has served The University of Texas at Austin in dozens of positions, such as helping select a new supercomputer center director and department chairs for mechanical engineering. But he recalls administrative work that affects people directly, such as leading the arduous task of updating mechanical engineering’s thermal-fluids curriculum for graduate students. “It’s not earth shaking, but it’s just one of those things that needs to be done so you persevere and you do it,” Moser says. “That’s the reason to be here at a university – to work with students and to mentor and help them. They teach me a lot, and I hope I teach them a little.”
Being a part of engineering advances provides a counterpoint along the way. In July, for instance, the third iteration of a device he and his CSEM Ph.D. student Nicholas Malaya helped design that captures the energy of dust devils was tested at the former proving grounds for General Motors’ cars in Mesa, Arizona. “We’re waiting anxiously to see how it works and hoping for the best,” he says, noting that the device could offer a cheap way to harvest a new energy source.
His legacy continues to grow beyond research. Both his sons are pursuing mechanical engineering degrees, despite early misgivings from one. “We thought for sure he was going to study computer science, but somehow he decided that what his mom and dad do was interesting after all.”
By Barbra A. Rodriguez