Slashdot Mirror
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.
Layer of Bubbles? How can Michael Jackson decrease fuel consumption.
With this knowledge, no one will be able to touch my son's boat at the next Boy Scout's boat race!!!
Why bother reinventing the wheel when they could just glue a bunch of air hockey tables to the outside of a boat?
have courage
It is a good way to hide something, except of course that a huge unaccounted for cloud of bubbles is fairly unusual, especially if it's steaming towards King's Bay Georgia at 15 knots.
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...
The first I ran across a similar concept (and one mentioned in TFA) was, in fact, on slashdot. It might have been this article, though that references earlier stories I couldn't find in a quick googling. Of course, the Scientific American article the /. writeup links to is MIA, so I can't be sure that's the blurb I'm thinking of.
/. for long enough, you've seen something like this before.
But yeah, if you've been reading
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 supercavitational bubble is vacuum, not air. This is also the reason why the torpedo cannot be manoeuvred with traditional means once fired (since there is no water anywhere around it).
Send email from the afterlife! Write your e-will at Dead Man's Switch.
Putting bubbles around a ship will decrease its displacement, thus making it sink more to compensate for the loss of displacement, it will sink until it displaces exactly the same weight in water as the ships weight.
A thin layer of bubbles will not do that. They will be at the pressure of the surrounding water and provide the necessary force to support the ship. To sink lower, the ship would have to move them 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.
Now if you have a DEEP foam of bubbles beneath and around the ship - allowing the air to move sideways rapidly - the ship would indeed drop as if it were in midair - or (if the foam is only partly air) attempting to "float" on something less dense than itself. But a layer of bubbles against the hull will not do that.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
TFA says the most promising method of getting the air cushion is to build cavities on the underside of the ship. It takes some energy to maintain the cavities full of air, but it's a lot less than the energy required for the other methods.
However, the Vikings used the same principle centuries ago. Their way of building ships creates longitudinal grooves along the bottom of the hull, which form cushions of air at higher speeds. The overall shape of the hull also contributes to low resistance. I don't have any proper references, as I only saw this in a documentary once, but for example here is a brief mention of the idea.
Escher was the first MC and Giger invented the HR department.
There has been a lot of theorizing that this is how some of the viking longships were so fast. Essentially the way the planks were laid out allowed the ship to catch air from in front of it and shove it underneath the boat, guiding it along its length. Look up the Gokstad ship for details.
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
More idiots adding more sh!t to the environment. We've already seen how the ocean provides the particulates and the water vapor for the clouds that keep the planet from going supernova...
I dislike greenies as much as the next guy, but adding polymer ejaculates to ships - battleships, ships of war, or just ships that have to go fast, to make them go faster or use less fuel.... ffs wtf are the thinking!?
From TFA: "The polymers probably won't damage the environment"
Let's start a famous quotes page, here are a few to kick things off:
Qld gov't: "The cane toads probably won't damage the environment"
B Gates: "You probably won't ever need more than 640k"
Local Dr: "This might sting a little bit"
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
then add some soap and La Voila!
Excuse me, but please get off my Pennisetum Clandestinum, eh!
IIRC, they have a couple of rocket-powered supersonic torpedos that panicked the US Navy when first demonstrated...
You're probably referring to the "Shkval" torpedo http://en.wikipedia.org/wiki/VA-111_ShkvalWhile certainly fast it's nowhere near supersonic, and furthermore it utilizes supercavitation http://en.wikipedia.org/wiki/Supercavitation
which is someting quite different from this technology.