Future Ships Could Float On Bubbles

MattSparkes writes, "Creating a layer of bubbles underneath a ship's hull could improve fuel efficiency by 20%. When you consider that 90% of the world's goods are transported by sea, the importance of this discovery is obvious. 'Conjured up from thin air at the flick of a switch, this slippery blanket will help transport a fully laden tanker or container ship across the ocean at higher speed, and using far less fuel, than ever before... There is currently no other technique in naval architecture that can promise such savings.'" The article looks in some detail at the engineering problems that will need to be overcome before this technique is practical.

Comments

But how will it affect buoyancy?

[with_him]

Since methane hydrates releases are still suspected in the sinking of ships, how do the researchers account for the loss of buoyancy? Since this research calls for redesign of current ship building know-how, how are they planning on addressing the buoyancy part of the equation? To read more check out this http://www.newscientist.com/article.ns?id=dn1350 and http://jbj.wordherders.net/archives/000992.html someone trying to weaponize the buoyancy concept. http://www.nexusresearchgroup.com/fun_science/buoy ant1.htm A fun science experiment for the kiddies, or others that want to understand it better.

In case anyone is interested

[noewun]

In what

The idea of air cavities has much in common with supercavitation, in which a submerged object such as a torpedo creates a single large bubble around itself. This slashes skin friction, bringing remarkable speeds within reach (New Scientist, 22 July 2000, p 26). Perhaps not surprisingly, Russian engineers who first developed supercavitating torpedoes have not only done plenty of research on air-cavity lubrication for ships, but have also put their ideas to work.

refers to: Shkval. Scared the bejesus out of the U.S. Navy.

This works best at slow speeds

[nels_tomlinson]

I haven't yet read the fine article. I do know just a bit about naval architecture. This should help with skin friction, which is the big deal at low speeds. For higher speeds, the resistance which comes from making the wake is the big deal, since the wave-making resistance increases roughly as the square of the speed.

So, what's ``low speed?'' That's probably going to be any speed much below sqrt(waterline length in feet), with units of knots. So, for a 400-foot long ship, anything less than 20 knots is in the speed range where this is likely to matter. For a 900 footer, anything less than 30 knots. Most ships travel in that low speed range, so this could be practical.

Yes and it has been in use for a while

[LWATCDR]

http://www.fas.org/man/dod-101/navy/docs/swos/stu2 /NEWIS9_7.html
Some people will confuse the idea of bubbles with cavitation. Cavitation is loud and is avoided but it is caused when a screw manages to cause a phase change. The water turns to vapor and the the bubble collapses making a lot of sound and can even erode the metal on the screw.
The bubble of air that the navy uses don't collapse so no noise instead it acts like an insulator.

I wonder if you could use the exhaust gases of the ship for the bubbles for shipping application? You would have to cool the gas first but it might be a bit if a free lunch.

Re:Not really the same.

[PWNT]

The supercavitation bubble negates the need for torpedoes that can steer.

Ships move slower than traditional torpedoes, however the relative difference is not huge, so a ship can attempt to evade the torpedo.

These new torpedoes travel so fast, that any amount of evasion is useless! IIRC the new torps are travelling at 200 knots, like 400 km/hr or something. This is a huge difference compared to older slow torpedoes travelling at 50 knots.

These very fast torpedoes would be used to sink the larger fleet carriers from submarines. Get under or anywhere near the carrier, shoot 3 at the carrier and go on a silent run to creep away.

Re:Not really the same.

[Anonymous Coward]

These new torpedoes travel so fast, that any amount of evasion is useless!

They are so fast you can't "see" them coming on sonar. LIDAR doesn't have very good range under water and RADAR doesn't work at all. If it was fired from enough below the surface that the shock wave doesn't hit the surface before you're hit, you'll never know it was coming.

Flapping Tails

[Garrett Fox]

It's also worth looking at MIT's RoboTuna and RoboPike, robotic fish, and the penguin boat Proteus. These projects demonstrate that fish-like fins or flippers substantially improve propulsion efficiency vs. propellers, because they generate vortices of water that actually push a vehicle forward. MIT sees these vortices as the answer to Gray's paradox, which said that a dolphin would have to be stronger than it is to swim as fast as it does. (That article disagrees.)

A flapping drive would also have the advantage of looking cool.