CU-Boulder Study Of Vortex Rings Leads To Design Of Better Vehicle Propulsion Systems

November 29, 2004

A University of Colorado at Boulder engineering professor may have found the key to developing more accurate and efficient propulsion systems by studying the formation of vortex rings, such as those made by squid and jellyfish to move themselves underwater.

Kamran Mohseni, an assistant professor of aerospace engineering sciences, says the results have several possible applications ranging from small, highly maneuverable, unmanned vehicles to steering mechanisms for miniaturized capsules that can travel back and forth through the human digestive tract to diagnose and treat disease.

Mohseni's research and collaboration on biomedical applications are described in the cover story, "Search for the Perfect Vortex," published in the Oct. 23-29 issue of New Scientist magazine.

Vortex rings are created when a burst of fluid shoots out of an opening. The fluid moves in one direction and then spreads out and curls back, like the rings blown by a smoker. Squid and jellyfish are natural experts at this, creating large vortex rings by squirting water out of their mouths to propel themselves quickly in the opposite direction.

Intrigued by the relationship between thrust and vortex rings, Mohseni built a computer simulation to model the way these rings form. By doing so, he wanted to learn how a thruster could best be designed to take advantage of this natural phenomenon.

"There are basically two ways to do this," Mohseni said. "One is to accelerate the piston during the ring's formation and the other is to increase the exit diameter as a function of time." The optimal design precisely matches the speed of the fluid emerging from the opening to the speed of the growing vortex ring.

Mohseni's research group is now incorporating the new vortex thruster design into various types of underwater vehicles. CU students already have built several prototype vehicles, which combine a sleek design with multiple small vortex thrusters, offering greater maneuverability at lower speeds than any other vehicles currently available. Possible applications include underwater scientific research and search and rescue operations where maneuverability and precise changes in direction are required.

Mohseni also is collaborating with Dr. Yang Chen at CU-Denver and Health Sciences Center on applications in medicine. Mohseni has applied for a patent on a device to improve endoscopy by creating remote-controlled capsules with miniature vortex ring thrusters that would allow the capsules to maneuver within the digestive track, recording images and dispersing medication at precise locations as needed.

Another possible application of the technology is for vertical takeoffs and landings of micro-air vehicles, which could be used to carry sensors for the investigation of environmental hazards and conditions, Mohseni said.

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