Boats that Swim

Receiving a single Multidisciplinary University Research Initiative (MURI) grant from the Department of Defense is a mark of distinction. The competition for them is fierce. In a recent year, 361 teams of researchers submitted preliminary proposals; of those, 88 were selected to provide more-detailed proposals. Only 24 projects were funded.

That’s why receiving two MURIs — as Associate Professor Hilary Bart-Smith has done — is extraordinary. A mechanical engineer, Bart-Smith is using nature as her inspiration for developing new, high-performance methods to propel underwater vehicles.

During her first MURI, Bart-Smith and her colleagues studied batoid rays, which include manta rays and cownose rays. Their work produced a better understanding of issues that affect their movements through the water, including wake structure, structural dynamics and kinematics.

For the second MURI, Bart-Smith and her colleagues, who include faculty members from Princeton, West Chester, Harvard and Lehigh universities and the University of Virginia, have chosen trout, tuna and dolphin to study. They each are fast, efficient swimmers, but have differences in their fin structures, mechanical properties and swimming mechanisms that make them a group ideal for study. “We want to be able to make a connection between performance and structure,” Bart-Smith says.

For each animal, Bart-Smith and her colleagues are determining the physics of the fluid-structure interaction between the body and fin/fluke and the water that produces efficient, high-speed motion. They also intend to move beyond the basic science, suggesting ways to improve on nature in next-generation human-made propulsors. “Biology finds the optimal solution based on its requirements,” Bart-Smith says. “An animal needs to find food, avoid becoming food for some other creature and mate successfully. We would like to determine a basis for maximizing characteristics like speed, maneuverability and stealth.”

Thanks to her work, Bart-Smith now knows much more about aquatic animals than she ever thought possible. “When I was growing up, I watched David Attenborough’s nature programs on the BBC,” she says. “At the time I was much more interested in chemistry and physics than biology. Thanks to my work on the MURI grants, I have a whole new appreciation for marine biology.”