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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.
Creating a layer of bubbles underneath a ship's hull could improve fuel efficiency by 20%
But have they tried rainbows and/or fairie dust?
The theory of relativity doesn't work right in Arkansas.
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.
have courage
Have they factored in the amount of energy required to create the layer of bubbles? Seems like creating a layer of bubbles around the hull of a giant ship would take quite a bit of energy.They are moderately intellegent people. They do think of these obvious things...
(For reference: It is a major problem for one of the approaches being researched, but only one. Another approach already has a 40% reduction in friction by diverting 3% of the ship's power. Well worth the expendeture.)
'Sensible' is a curse word.
When you consider that 90% of the world's goods are transported by sea
Bzzzt. The submitter misstated the article, so this statement is flat out wrong.
From the article (emphasis mine):
in 2003 more than 90 per cent of all goods that were sent around the globe went by ship
So in the context of global shipping, 90% of goods are transported by sea. Obviously far, far less than 90% of the world's goods are transported globally in the first place.
Dan East
Better known as 318230.
refers to: Shkval. Scared the bejesus out of the U.S. Navy.
I am a believer of momentum and curves.
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.
See what I've been reading.
The Russians already use it, but mostly for speed. It isn't all that usefull for stealth. (As already mentioned.)
So it's not useful for submarines, but for many surface ships it is very useful. And for torpedos it is killer. IIRC, they have a couple of rocket-powered supersonic torpedos that panicked the US Navy when first demonstrated...
'Sensible' is a curse word.
Uh, creating bubbles by cavitation is entirely different, happens for an entirely different reason, and has nothing whatsoever to do with this. YOU WIN TEH PRIZE!
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
What they ought to do is replace the oceans with frictionless liquid helium. That would be way more effective.
Reality has a conservative bias: it conserves mass, energy, momentum...
Believe you are taking about the Prairie-Masker system http://en.wikipedia.org/wiki/Prairie-Masker
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.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
"Junior! What are those bubbles in the bathtub?"
"Just reducing drag, Ma."
This is my post. There are many others like it. If you don't like what you read here, go try one of the others.
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.
To sink lower, the ship would have to move [the bubbles] aside - which it is already doing - but are limited in their ability to move by the resistance of the surrounding water. Meanwhile they are continuously replaced from the air source.
To make it clearer: If the boat sinks further the layer of air goes with it and stays about the same thickness. What is displaced is water. So the craft remains bouyant, as if the layer of air were part of its own structure, rather than part of the supporting water.
In fact, because the layer of air is "part of its own structure" and displaces its own volume of water, the craft itself will float HIGHER by about the thickness of the layer of air. (The air will be somewhat compressed and thus denser than the atmosphere, so it will raise the ship by a smidgeon less than its own thickness.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
The idea, while novel, is not new. The idea of a "100 knot Torpedo" has been around for awhile. The idea was to basically blow compressed air through a nozzle in the nose of the torpedo enveloping the torpedo in a "shroud" of air, as opposed to water, thus drastically reducing drag resulting from moving through the water.
The idea, when applied to a ship, has nothing to do with bouyancy(although it would certainly effect it) but rather reducing drag by displacing the water around the hull with air. While impossible to entirely remove the contact with water, even small decreases will reduce drag enough to make the whole idea worthwhile in terms of fuel consumption.
The problem with BOTH ideas is the interference with propulsion. A propeller does not work as efficiently in the same mass of air bubbles. Unless some means of keeping the prop out of the bubble cloud is devised, the resulting loss of propulsion will offset the gains made by the reduction of drag. This is the main reason the "100 knot Torpedo" is not used.
As far as noise reduction in submarine warfare, it is NOT quieter. Its simply different. It is akin to a propeller "cavitating", and in submarine warfare, that is like sending up a signal flare.
What they are talking about here us just surrounding the hull with a thin layer of bubbles.....maybe the ship sits a couple inches (to pull a guess out of my rear) lower in the water....but there's not going to be any danger of sinking a ship...
Actually it floats HIGHER - by about the thickness of the air film. (It would float higher by EXACTLY the thickness of the air film except that the film is compressed slightly by the higher water pressure at the bottom of the boat.)
To understand it:
- The film displaces water, just like the hull.
- If the hull sinks marginally, the film stays about the same thickness and it's the water below that is displaced.
- So the film of air acts like part of the hull.
- The total amount of water displaced is the amount displaced by the hull PLUS the amount displaced by the air.
- But the air under the boat is about the same density as the air above the boat. So only the craft's weight (plus any surplus weight of air from its compression by the higher pressure below the hull) is supported by the displaced water.
- Thus, to displace its own weight the hull plus air system must have the hull higher than the hull-only system by about the thickness of the air barrier.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
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.
Revive the Constitution.
FTFA linked by grandparent:
Gas. Not vacuum. The first thing I thought when I heard about the Shkval is "I wonder if the technology could be useful at ship-sized scales?", the first thing I thought when I saw the article here on slashdot was "Woo, supercavitating!"
j'ai découvert une démonstration vraiment admirable (de ce théorème général) que cette si