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Breakthrough Could Lead to Faster Ships
Friday, November 8, 2002
By Rudi Williams
American Forces Press Service

She said, today, the average speed for transit from the United States to Saudi Arabia, for example, is about 20 to 25 knots. "The carriers, for example, can go faster, but they don't because you can only go as fast as your slowest ship. So if you can raise everybody else's speed to the carrier's, you've actually accomplished something."

WASHINGTON -- AFIS
The idea's not ready for prime time, but Defense Advanced Research Projects Agency researchers here have made a breakthrough that could mean faster, longer-range ships and millions of dollars in fuel savings.

DARPA program manager Lisa Porter said 14 teams are working on reducing "friction drag" as ships sail through water. Program participants include teams from, the universities of Michigan, Delaware, Illinois and Washington (St. Louis, Mo.); Stanford, Pennsylvania State, and Brown universities; Texas A&M; and the Office of Naval Research.

There are different components of drag, but the program Porter is leading focuses on "friction drag." "It's the friction between the water and the ship's surface," she explained. "As you move through the water, your ship is dragging along a certain volume of water with it. That's because you have friction between the water and the ship's hull. And that's slowing you down."

As ships move through water, they create vortices that cause drag. "When you think of a vortex, you might think of a tornado and that's exactly analogous," Porter said. "We're talking about little, tiny swirling motions that mix up the flow and make it what we call turbulent."

Making ship's surfaces smoother was once considered as a way to reduce friction drag. In practice, Porter said, "It doesn't work too well because fouling and microorganisms keep the surface from remaining smooth enough to make a difference."

Decades of lab testing revealed that polymers and "microbubbles" were promising technologies that might reduce friction drag by as much as 80 percent. Up until now, however, no one had figured out how to apply the technologies to full-size ships, she said.
(More: DoD News Source)
2002 © The United States Department of Defense.

Dan