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posted by martyb on Friday April 12 2019, @01:33AM   Printer-friendly
from the ship-sliding-away♩♪♫ dept.

Phys.org:

ARES ["Air-retaining Surfaces"] studies novel ship coatings, by means of which an air layer is permanently retained under water, which considerably reduces frictional resistance of surfaces. At the same time, release of toxic substances from ship paints and biofilms (fouling) and corrosion is prevented by the air envelope between the ship and the water. Coordinator Thomas Schimmel, who works at the Institute of Applied Physics (APH), the Institute of Nanotechnology (INT), and the Material Research Center for Energy Systems (MZE) of KIT[*], and his group develop air-retaining surfaces under water based on the salvinia effect.

The salvinia effect studied by physicist Professor Thomas Schimmel of KIT and botanist Professor Wilhelm Barthlott of Bonn University in close collaboration with fluid mechanics expert Professor Alfred Lederer of Rostock University enables certain plants, such as the aquatic fern Salvinia molesta, to breathe under water. For this purpose, the aquatic fern is covered with special hairs that resemble small whisks and are characterized by a special chemical heterogeneity: while the individual hairs are water-repellent, each single hair has a water-attracting tip that adheres to water and permanently stabilizes the retained air layer.

[*] KIT: Karlsruhe Institute of Technology.

The project reports the team has demonstrated a 20% reduction in friction between ships and water, an efficiency gain with large implications for global shipping.


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  • (Score: 3, Interesting) by Runaway1956 on Friday April 12 2019, @02:18AM (1 child)

    by Runaway1956 (2926) Subscriber Badge on Friday April 12 2019, @02:18AM (#828432) Journal

    "We demonstrated that the Air Coating technology reduces friction by about 20%, as friction between ship and water is replaced by friction between ship and air," Thomas Schimmel explains.

    If the craft is moving through the water, with a permanently attached bubble of air under it, then there is no friction between ship and air. The friction is between air and water. Maybe if I read the article a few more times, his phrasing will make sense, but at this point, I see no friction between ship and air, until you get up above the water line.

    • (Score: 4, Informative) by c0lo on Friday April 12 2019, @03:51AM

      by c0lo (156) Subscriber Badge on Friday April 12 2019, @03:51AM (#828465) Journal

      Friction between trapped air and water will cause the air to start moving inside the 'micro-/nano-cavities' they are trapped in.
      The movement of air will transmit part of that friction to whatever is bound to the ship's wall and defines the cavities.

      --
      https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
  • (Score: 0) by Anonymous Coward on Friday April 12 2019, @03:47AM (2 children)

    by Anonymous Coward on Friday April 12 2019, @03:47AM (#828460)

    When can I get my supercavitating submarine and supercavitating torpedoes?

    • (Score: 2) by Bot on Friday April 12 2019, @05:42AM (1 child)

      by Bot (3902) on Friday April 12 2019, @05:42AM (#828500) Journal

      Some time after the supercavitating condom. Get your priorities straight and hard.

      --
      Account abandoned.
  • (Score: 2) by Spamalope on Friday April 12 2019, @08:48AM (2 children)

    by Spamalope (5233) on Friday April 12 2019, @08:48AM (#828532) Homepage

    You'd have the hull coated with tiny hairs. Assuming they were somehow durable enough, how would you keep it clean?!? Things grow on boat hulls as soon as they hit the water... It'd have to prevent any algae and barnacle growth or the coating would fail before the ship while the ship was loaded with cargo the first time.

    • (Score: 0) by Anonymous Coward on Friday April 12 2019, @01:26PM

      by Anonymous Coward on Friday April 12 2019, @01:26PM (#828578)

      > You'd have the hull coated with tiny hairs.

      I wonder if there is any relation to the drag reduction from riblets? This
      https://www.sciencedirect.com/science/article/pii/S2405451816300484 [sciencedirect.com]
      looks like a nice overview (full text at the link).

    • (Score: 2) by Runaway1956 on Friday April 12 2019, @01:43PM

      by Runaway1956 (2926) Subscriber Badge on Friday April 12 2019, @01:43PM (#828583) Journal

      Things grow on boat hulls as soon as they hit the water

      My impression from the article was, the hull doesn't hit the water. Those things that grow on boat hulls in water, won't get the opportunity, unless they figure out a way to dangle their respiratory organs down into the water. I don't reckon microscopic critters can achieve that feat. Larger critters might, but they may not enjoy the experience, so not try. But, most larger creatures that attach themselves to hulls are microscopic when they begin life, and start searching for something to anchor themselves to.

  • (Score: 1, Interesting) by Anonymous Coward on Friday April 12 2019, @09:49AM

    by Anonymous Coward on Friday April 12 2019, @09:49AM (#828535)

    This was the motivation behind a research which ended up with invention of hovercraft. Only they intended to replenish the air bubbles by pumping compressed air through a sieve.

    IMHO, there is another, poorly investigated track of using passively rotating (they would have too flimsy traction for propulsion if they were active) floaters to reduce friction between water and a vessel.
    But then again, the bearings on such a thing would take to much punishment in high seas, and the lubrication would be a bitch.

  • (Score: 2) by ledow on Friday April 12 2019, @12:53PM (1 child)

    by ledow (5567) on Friday April 12 2019, @12:53PM (#828569) Homepage

    I'm sure I read somewhere that one of the best ways to sink a ship is to surround the water in bubbles.

    I'm sure they've done their research and stuff, but it seems that if it works to significantly reduce friction enough to bolt a system onto a ship, it also risks becoming a hazard in terms of buoyancy?

    I'm not at all certain that putting air into the sea-metal mix will reduce corrosion or algae either.

    • (Score: 4, Informative) by Runaway1956 on Friday April 12 2019, @01:51PM

      by Runaway1956 (2926) Subscriber Badge on Friday April 12 2019, @01:51PM (#828584) Journal

      Part of the thing about bubbles of water and sinking ships, is to localize the bubbles. Certain torpedoes create large bubbles, thus removing the support from beneath the ship, at one end, or in the middle. The ship's back is broken, trying to support the suddenly "heavy" portion of the ship hanging over "nothing". With a uniform film of air, support is equal all the length of the ship, so no broken keel. And, "film" is also part of the secret. There aren't any bubbles bobbing around, and floating to the surface. Each little plate has it's own permanent film of air. TFA claims that they've had some of this stuff submerged for five years, and still haven't lost the film.

      Of course, putting the stuff into real life use, we may see entirely different results than they have achieved in the lab.

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