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BOXFISH AN INSPIRATION FOR ODU PROFESSOR

At first glance, the boxfish looks prehistoric and about as sleek as a brick. But Old Dominion University marine biologist Ian Bartol has found the tropical fish to be an efficient swimmer with maneuverability and stability that may make it the shape of things to come.

When German engineers-whose affiliation he was never sure of-contacted Bartol several years ago, he gladly shared information about his work. So he couldn't help but feel proud this summer when Mercedes-Benz unveiled a concept car that was developed in Germany and is inspired by the boxfish. With a 140-horsepower diesel engine, the four-passenger concept car has delivered more than 80 miles per gallon in steady highway travel, according to the automaker.

An article about the new vehicle in The Scientist magazine this summer relied heavily upon Bartol's explanation of what is so special about the design of the fish.

"It's exciting that Mercedes-Benz has used the boxfish, but understandable, because it expresses so well the design constraints of a car: rigid, low drag and a big cross-section," Bartol told The Scientist. He said the concept car is a good example of "how some of nature's solutions together with human ingenuity and creativity can help advance technology."

As the article notes, Bartol has done boxfish research for the Office of Naval Research that could influence the Navy's design of small, unmanned submarines. He is an assistant professor of biological sciences who joined the ODU faculty in 2003.

Boxfish became a focus of Bartol's professional interests when he was doing postdoctoral research from 2000-03 at UCLA, Cal Tech and Woods Hole Oceanographic Institution. "We noted that it could swim in smooth trajectories, even in highly energetic, turbulent waters," he explained. A typical boxfish environment includes coral reefs and shallow waters where there are wave-generated perturbations.

Building on earlier research that characterized the awkward-looking boxfish as a fast and nimble swimmer, Bartol and several colleagues took on the task of finding out what it is about the fish's morphologies that keep it stable during quick movements, even in turbulent water.

In two papers published in 2002 and 2005 in The Journal of Experimental Biology, the team led by Bartol showed how unusual contouring and other physical characteristics produce self-correcting forces for four species of boxfish. When swimming maneuvers or perturbations threaten to toss the fish topsy-turvy, their contours develop spiral vortices-like tiny whirlpools-alongside them as they swim and the resulting pressure differences bring about the self-corrections.
Whereas design principles in nature and engineering usually require trade-offs between stability and maneuverability, the boxfish design does not gain one at the expense of the other, Bartol said.

The shape of the Mercedes-Benz concept car is faithful to the boxfish, with very similar overall shape and flow channels. Bartol said fish have long been used as models for sleek, low-flow-resistance vehicles, but that most fish shapes are not boxy enough to allow for passenger compartments. Also, most fish have soft, flexible bodies, whereas the boxfish has a rigid outer shell that makes it more practical for use as a model for a rigid automobile. (Mercedes-Benz engineers reported that they increased the concept car's rigidity and decreased its weight by taking construction tips from the boxfish skeleton.)

Bartol said he hopes Mercedes-Benz produces the boxfish concept car, but that he has heard nothing about the automaker's plans. "I'm wondering when I'll get my free car," he added with a smile.

Early efforts of the young scientist to create precise replicas of spotted boxfish forced him to make some interesting trips to medical computer tomography laboratories that normally produce the three-dimensional CT scans (similar to the original CAT scans) on humans. "I went there with my fish and I got lots of strange looks from patients sitting with me in the waiting room," he said.

Recently he acquired a state-of-the-art Defocusing Digital Particle Image Velocimetry (DDPIV) device that uses laser illumination, reflective particles and a sophisticated, three-lens camera to capture a three-dimensional image of water flow over the exterior of a boxfish model or actively swimming fishes and squids.
Current research by Bartol in his field of marine-organism biomechanics includes studies of how squid of various sizes move through the water. He is looking in this National Science Foundation-funded project at the relationship of squid size to efficiency of jet propulsion.

Bartol said word of the DDPIV capabilities quickly reached the aeronautical engineers at ODU's Frank Batten College of Engineering and Technology, whose research can be very similar to his. He presented a seminar on his boxfish and squid swimming research to the engineers, in which he introduced the DDPIV technique. "They are excited about it and it has gotten us to talking more" about interdisciplinary projects, he said.

This article was posted on: October 2, 2006

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