Anti-Wave Tech Tricks Ocean Water Into Standing Still, Making Ships Efficient and Invisible

By Rebecca Boyle Posted 08.12.2011 at 1:27 pm 13 Comments

U.S. Navy Ships at Sea Wikimedia Commons

We’ve already seen how future ships can be cloaked against sonar, and maybe someday even space and time. Now researchers say they can cloak the ships’ wakes, tricking water itself into acting as though nothing is there.

A new metamaterial cloaking system can trick water into standing still as an object moves through it, by eliminating the shear force and reducing water displacement, Duke University researchers say. This in turn reduces the amount of energy required to move an object — say, a ship — through the water, theoretically saving fuel.

Yaroslav Urzhumov, assistant research professor in electrical and computer engineering at Duke, envisions covering the hull of a ship with a three-dimensional lattice of porous metallic materials that would be embedded with tiny pumps. The pumps could force flowing water through at variable rates, Urzhumov says in a news release. “The goal is make it so the water passing through the porous material leaves the cloak at the same speed as the water surrounding by the vessel,” he says.

The water surrounding the hull would appear to be still, relative to the movement of the vessel, which would reduce the amount of energy the vessel needs to get through it. When moving through a fluid, a solid object displaces a greater volume of fluid than its own total volume — think of how much effort it requires to drag a thin fishing line through water. So if these shear forces could be eliminated or mitigated, a moving vessel would displace less fluid.

We’ve seen other examples of ship-efficiency water interference tech lately, including a proposal to harness the Leidenfrost effect, wherein a liquid produces an insulating vapor layer when it comes in contact with a solid object that is hotter than its boiling point. That vapor layer could reduce drag, researchers say. But superheating hulls would likely require lots of energy input, lessening any energy savings from the drag reduction.

A lattice-pump system would conceivably be better, because the micropumps wouldn’t need that much power, Urzhumov says — certainly not as much energy as you would need to push an un-cloaked ship through the seas. The research is reported in the online version of Physical Review Letters.

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13 Comments

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Prbsolver

08/12/11 at 1:41 pm

Wonder how they plan on keeping the "Pumps" clean of barnacles.. Maybe a lil Medetomidine

http://www.popsci.com/science/article/2011-06/barnacles-destroy-boats-getting-rid-them-destroys-sea%E2%80%94until-now

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3ddraft

08/12/11 at 2:25 pm

I'm pretty sure that given the chance to make their ships harder to detect, the military of any nation would do what it takes to keep those pumps clean. It's amazing what they're doing with the meta-materials.

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-my name here-

08/12/11 at 2:43 pm

if the ship displaces less water, than it would also have to be made of lighter materials than the currently used steel, as it would be less buoyant.

why learn from your own mistakes, when you could learn from the mistakes of others?

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canterol

08/12/11 at 3:57 pm

@my name here

I think they mean the water displaced outward away from the ship (it does not come back to its original position after the boat passes.)

It would still displace the same volume of water, but the water near the surface would have the same velocity after the ship passed then it did before the ship disturbed it.

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canterol

08/12/11 at 4:18 pm

Edit...
Macroscopically, the water does go back to it's original position (Wake is energy translating through the water... not so much the water itself). But as the water fills in the gap the boat left, it flows differently than the surrounding water and creates all sorts of fun hydrodynamic effects. The metamaterial, I would assume, stops that "rush" of water trying to return to equilibrium by introducing a counterflow that tricks the water into thinking it was never disturbed.

Still, the boat displaces the same volume of water.

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jefro

08/12/11 at 5:46 pm

OH, I get it. Teflon coating the bottom of the hull.

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aarontco

08/13/11 at 6:46 pm

The array of pumps, however, may substantially add to the noise signature of the vessel, making it more detectable via acoustic means. Let's face it, if you really want to find a slow-moving ship these days, you can find them via satellite. As far as the Leidenfrost effect, that sounds beyond ridiculous, and would add to the heat signature of the vessel.

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RobWiki

08/15/11 at 2:25 pm

While the Leidenfrost effect seems like a bad idea for a full ship, has anyone thought of using it for a torpedo? I think it could make counter measures more difficult and you're talking about heating a much smaller "vessel" for a shorter amount of time.

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sunsnow

08/17/11 at 4:02 am

Why is it that all I can think about is water skiing behind a wakeless ski boat now?

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drchuck1

08/17/11 at 4:35 pm

that would be no fun, a moving boat forces water away from its hull, effectively displacing more water than is actually needed to float, energy transfers to the water that reduces efficency

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zaggy123

08/20/11 at 12:05 pm

Has Anyone thought about potential technology, similar to this for canceling out noise? Say if you could have a constant input of data translating into the sound waves needed to cancel out noise, say in a crowd or in a football stadium?

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