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Fluids passing over objects can set up vortices- with potentially disastrous consequences. Technology can capture energy from the turbulence and convert it into clean, cheap electricity.
THE EXPERIMENTAL SET-UP WAS SOLID, BUT IT DIDN'T LOOK EARTHSHATTERING. My graduate students had built four matched cylinders, each 36 inches long and 3.5 inches in diameter. All four were attached to support structures and immersed in a flow tank in the Marine Renewable Energy Laboratory at the University of Michigan in Ann Arbor.
When the impeller was turned on and water flowed through the tank, however, something amazing happened. The cylinders started to move up and down through the water, and then they began to move in sequence, almost as if they were part of a four-piston reciprocating engine. The motion, first up, then down, was so forceful that it was evident that the cylinders were tapping into some large supply of energy.
All this in water flowing at just 2.6 knots.
The experiment, which was conducted this winter, was the latest in a series at the University of Michigan to help prove the value of a novel, environmentally compatible, and potentially important energy harvesting technology. The cylinders in the tank are being moved by vortices in the water that form and then shed. We don't have data yet for this experiment but according to our calculations, a matrix of such columns in a steadily flowing ocean current or a river could generate hundreds, even thousands of watts per cubic meter depending on the flow velocity. In an area far smaller than a typical wind farm, an array of these cylinders could produce 1 gigawatt of power, enough to light a medium-size city.
ENGINEERS HAVE BEEN AWARE OF VORTEX-INDUCED VIBRATIONS FOR CENTURIES. In fact, Leonardo da Vinci first observed VIVs some five hundred years ago, in the form of "Aeolian Tones," the sound made as wind passes over a wire of the correct diameter and tension, and in the vortices that swirl behind the piers of a bridge. At the latter half of the 19th century and the beginning of the 20th, researchers such as John Strutt (Lord Rayleigh) and Theodore von Karman discovered that strings in a wind move perpendicular to the flow of air, and...