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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.
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.
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.
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.
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).
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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.
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
How large of a sail would it take to provide worthwhile trust to a 100,000 ton container ship, I wonder?
c hooner
A 170 ton Schooner uses 700 square feet of sail...
Assuming a linear sail:weight relation, that'd mean 400,000 sq feet of sail. Over 600 feet square. I wonder how your average sail material would hold up when scaled that large; additionally, what sort of mast and rigging would be required? How would you adjust the sails, anyway, when the deck is covered in thousands of 40 foot containers? Would all of this merit the additional weight?
Oh, and on top of that, a container ship travels twice as fast as a schooner.
http://en.wikipedia.org/wiki/Shenandoah_Topsail_S
http://en.wikipedia.org/wiki/Emma_M%C3%A6rsk
Were sticking a sail on a container ship practical, they'd probably have done it by now.
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.