using eddy currents/vorticies to generate power in fluids/gases

Much like new fangled performance swim suits take advantage of strategically placed bumps to facilitate faster swimming, there's been some improvement related to fluid dynamics and power production.

This article points out the basics of the technology, which is under development in Michael Bernitsas' lab at the University of Michigan.

Clean Power Tapped From Swirling Currents
Emily Sohn, Discovery News

Dec. 15, 2008 -- Currents can be powerful enough to tip canoes, damage docks and even topple bridges. The force of all that moving water can also provide a clean, affordable and unobtrusive source of renewable energy, says engineer Michael Bernitsas, of the University of Michigan in Ann Arbor.

Bernitsas has invented a device, named VIVACE, that converts river and ocean currents into electricity. Like fish, the device takes advantage of powerful phenomena called vortex-induced vibrations.

These vibrations occur when water flows past a round or cylindrical object. Swirls of water form downstream from the object and in an alternating pattern on either side of it. That causes the object to oscillate, or vibrate, up and down.

Vortex-induced vibrations also occur in air. And they have been responsible for some high-profile disasters, including the 1940 collapse of the Tacoma Narrows Bridge in Washington.

(you'll have to follow the link for the rest of the article)