By  Wende Whitman
Daniel Quinn

Did you know that a tuna is a super swimmer?

“They’re really fast, they’re really strong, they’re big, they’re at the top of their food chain without any natural predators. They’re a model organism for roboticists because they’re phenomenal swimmers,” said Daniel Quinn, University of Virginia assistant professor of Mechanical and Aerospace Engineering and Electrical and Computer Engineering and director of the Smart Fluid Systems Lab. “Besides being fast, tuna dart back and forth very quickly — complex, high-speed maneuvers — and we’re not sure how they do it.”

Quinn received a CAREER Award from the National Science Foundation to find out. The award is one of the nation’s most prestigious grants for early-career faculty who have the potential to serve as academic role models in research and education and to lead advances in the mission of their department or organization.

Quinn’s lab is using a tuna model rigged up to “swim” inside a tank to try to discover how liquids flow past the fish ­— a process called fluid dynamics — and govern high-speed, irregular or “asymmetric” swimming. By mapping out these flows, bio-inspired roboticists who have to rely on models of low-speed, regular or “symmetric” movements when designing and testing robots, will have the information they need to start modeling and designing fast, highly maneuverable water and aerial drones. Even though Quinn is studying swimming, the principles of fluid dynamics apply to water and air propulsion, so his research will inform both.

“We’ll be creating the first-ever flow visualizations of bio-inspired robots darting side-to-side,” Quinn said. “Our measurements could lay the groundwork for a new generation of intelligent swimming and flying machines.

“Part of the promise of these small, cheap vehicles is that they can be used en masse. Schools of tiny drones will be able to help with things like search and rescue, terrain mapping, or weather or climate tracking — all without disturbing the environment. They’ll let us study ecosystems in ways that aren’t currently possible with big, bulky propeller-driven vehicles, and they’ll help us to be better stewards of the natural world by reducing our footprint as we do our research,” he said.

Quinn’s test rig is highly sophisticated. The large, rectangular tank is a real water channel that houses a robotic tuna able to swim at a speed of 7 hertz, which means beating its tail seven times per second.

“There are two unique aspects to this rig,” Quinn said. “One, you can swim extremely fast, and two, you can move back and forth to maneuver.

“If you’re going to go super-fast, it’s really important that you can steer!” Quinn said. “In the natural world, you can’t do repeatable experiments on turning, since fish never turn the same way twice. The test rig gives us a controlled environment where we can produce and analyze turns in a repeatable way—it’s the only way to guarantee we’re uncovering the true physics of turning.”

Quinn’s team has also created artificial tendons for the tail fin of the robotic test fish so they can discover why and how “tail tensioning” affects swimming.  

robotic tuna in water

Testing Tuna Robots to Discover How They Maneuver

UVA Smart Fluids Lab team builds extensive testing rig to study and replicate a tuna's skillfull maneverability--especially darting back and forth.

If that weren’t enough, the project integrates educational activities, too, including virtual tours during which students from rural high schools teleconference into the lab and remotely control a robotic swimming rig. Quinn believes that outreach to high school students who may not be able to physically visit a lab in person is important, whether it’s because they live too far away or because of the coronavirus.

Quinn first got the remote-control idea last year when the coronavirus caused a cessation of in-person classes and briefly closed labs on UVA’s Grounds. He and his team were able to meet via Zoom and conduct tests remotely.

“Since the second half of the semester was supposed to be a hands-on robotics final project, I thought COVID would ruin the whole class. Instead, one student volunteered to take one of the robotics rigs back to her apartment and set up a webcam and remote access so that other students could run tests remotely. It was pretty cool."

When asked what attracts him to this research, Quinn said, “I think of myself first and foremost as a teacher, a mentor. What gets me out of bed in the morning is encouraging other people to be curious about the world around them.

“I think fluid dynamics is a really rich area for applying science to the natural environment. It uses a lot of abstract math and physics, but it also has direct applications—you can use it to build machines that impact people’s lives.”

He also said he is fascinated by the intersection of the cyber and physical worlds.

“I came to UVA to join colleagues in my department and at the UVA Link Lab who were interested in the same thing,” he said. “I want to explore how the old science of fluid dynamics can inform the new science of cyber-physical systems.”

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