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New Ship Will Remain Stable By Creating Its Own Inner Waves

Soulskill posted about 7 months ago | from the wave-of-the-future dept.

Transportation 43

Zothecula writes "When offshore oil drilling rigs are being installed, serviced or dismantled, the workers typically stay in cabins located on adjacent floating platforms. These semi-submersible platforms are towed into place (or travel under their own power) and then their hulls are partially filled with water, allowing them to remain somewhat stable in the pitching seas. Now, a ship is being built to serve the same purpose, but that will be a much more mobile alternative. It will keep from rolling with the waves by generating its own waves, inside its hull."

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43 comments

It's about time (4, Funny)

Anonymous Coward | about 7 months ago | (#44778953)

I used to do that in my bathtub. It's nice to see someone finally upscaled it like this.

Re:It's about time (1)

K. S. Kyosuke (729550) | about 7 months ago | (#44779385)

It's nice to see someone finally upscaled it like this.

I'm trying to imagine an ocean-going ship stabilized by upscaled ACs rolling in tubs and the first thing that comes to my mind is "it's 1912 all over again!"

Kerry, Obama fallater (-1)

Anonymous Coward | about 7 months ago | (#44779071)

I don't expect you are trying to assert that in such a case a spokesman of the administration telling us that the reason we are planning to engage in an act of war is something he cannot speak of. Is he a) telling us we cannot know the reason? b) lying? c) telling us he does not know the reason? or what? None of these cases are even remotely acceptable. We aren't talking here about raising taxes or birth certificates you know, people are going to die based on this.

And Kerry, good grief.

Wait, wait, wait...

Kerry's new defense for action in Syria is that if we DON'T intervene, MORE extremists will be attracted to the cause.

LOLWUT?!

Old and Busted: Intervention Incites Extremism

New Hotness: Nonintervention Incites Extremism

BEYOND. PARODY.

Carbon is an chemical element. (-1)

Anonymous Coward | about 7 months ago | (#44779087)

Carbon is an chemical element.

Smoke is made of carbon.

Chris Stevens died of smoke inhalation.

I guess Pres. Obama doesn't care when our enemies use chemicals to kill Americans.

He must have drawn his Red Line at YouTube videos.

Need that for my water bed (1)

JoeyRox (2711699) | about 7 months ago | (#44779147)

To helps me gets my grooves on without losing my babe inside the folds of my water bed.

Re:Need that for my water bed (0)

Anonymous Coward | about 7 months ago | (#44779321)

You're gonna fill your inflatable doll with water???

Re:Need that for my water bed (4, Funny)

gsgriffin (1195771) | about 7 months ago | (#44779503)

I'm glad you clarified 'folds' as being a part of your bed and not you.

Re:Need that for my water bed (0)

Anonymous Coward | about 7 months ago | (#44779959)

I need it for the other reason. I wonder if it would work?

HER own waves (0)

Anonymous Coward | about 7 months ago | (#44779177)

Where I come from, we still refer to ships with the feminine pronoun.

Power requirements? (5, Informative)

danceswithtrees (968154) | about 7 months ago | (#44779215)

The system pushes water from side to side using compressed air to counteract rolling from ocean waves. Granted this is for use in drilling rigs (read big money), but I wonder how much power is required to run the air compressors. The compressors have to be high flow to rapidly move a lot of water, albeit at relatively low pressures-- only 4.4 psi required to generate 10ft difference in seawater (this does not take into account viscosity and inertia).

Re:Power requirements? (2, Informative)

Anonymous Coward | about 7 months ago | (#44779287)

The system pushes water from side to side using compressed air to counteract rolling from ocean waves.

The two articles linked above both say the waves move the water and air valves are used to control that movement. I read that as this is a passive system fine tuned by controlling the rate air can escape and reenter at the ends of the U shaped tubes. I don't see any links to more details.

Re:Power requirements? (1)

Charliemopps (1157495) | about 7 months ago | (#44779601)

It doesn't take a lot of power. Aquarium guys do it all the time.
http://www.youtube.com/watch?v=QHfDh4eqYPs [youtube.com]

I doubt the system can make quick changes though so a violent storm or rouge wave couldn't be compensated for. But steady constant waves would be easy.

Re:Power requirements? (3, Informative)

danceswithtrees (968154) | about 7 months ago | (#44780097)

That is a different problem and not a fair comparison. The wave in an aquarium is being stimulated at the natural resonant frequency. If you slosh the water in a tank without the wave device, it will go back and forth at its natural frequency losing a little bit of energy with each slosh. In much the same way that you can maintain the swinging of a heavy pendulum with very little energy, the wave thingy you reference is energizing the wave at the natural frequency of the tank. If you were to try to make waves at 70% or 124% of the natural frequency, I think it would take MUCH more energy.

You can't reasonably expect the ocean to rock the boat at the resonant frequency of the internal water tanks. Therefore the ship's internal wave system is going be expending a considerable amount of energy. Ships weigh tons. To counteract the rolling motion of a several ton ship, you are going to have to move several tons of water several times per minute.

Re:Power requirements? (2)

jbengt (874751) | about 7 months ago | (#44780483)

You can't reasonably expect the ocean to rock the boat at the resonant frequency of the internal water tanks. Therefore the ship's internal wave system is going be expending a considerable amount of energy.

You can if you tune the resonant frequency of the tanks to the general frequency of the waves and use the air valves TFA talks about to fine tune the resonance. I know, for example that tuned water tanks are sometimes used to dampen swaying of high-rise buildings.

Re:Power requirements? (0)

Anonymous Coward | about 7 months ago | (#44781601)

The tuned dampeners in buildings though are tuned to the swaying frequency of the building, which doesn't vary much and has a lot more to do with the construction of the building and the stuff around it. The waves a ship is exposed can vary over a much wider scale of frequencies.

Re:Power requirements? (1)

jbengt (874751) | about 7 months ago | (#44844587)

Thus the ability to tune the resonant frequency against the waves using the air valves.

Re:Power requirements? (0)

Anonymous Coward | about 7 months ago | (#44782671)

You can't reasonably expect the ocean to rock the boat at the resonant frequency of the internal water tanks.

Yes, we can. A boat has a natural frequency of its own. That's the resonant frequency at which it rolls from side to side. Any ship is a resonant band-pass filter. And obviously you tune your internal water tanks to band-stop that exact frequency. That frequency is the source of all trouble - all other frequencies are dampened sufficiently by the ship as it is - no resonance.

Re:Power requirements? (1)

SirCowMan (1309199) | about 7 months ago | (#44783015)

The volume of water will be on order of 2% of the vessels overall weight, so yes it will be a massive amount of weight. Most of the roll-dampening is provided by the hull's natural resistance to roll and the center of mass of the vessel typically being low. This system itself works not by moving the water per-se, but by controlling the natural roll of the water within the U-shaped tank to counteract that motion. By adjusting the air valves, the natural frequency of the tank can be modified (the response curve flattens out). Otherwise, the tanks or combination of tanks are selected to match the natural roll period of the vessel.

Re: Power requirements? (0)

Anonymous Coward | about 7 months ago | (#44786341)

Rouge waves? I fail to see how the color of the wave makes a difference.

SWATH doesn't require power (4, Informative)

CanadianRealist (1258974) | about 7 months ago | (#44780563)

Small Waterplane Area Twin Hull (SWATH) [wikipedia.org] is a design that minimizes the effect of the waves. Most of the volume that supports the ship is below the level of the waves, making it very stable. The stability comes from the hull design, so it doesn't require any power and the stabilization isn't prone to failure like an active system.

Here's a short video [youtube.com] of a SWATH ship in rough seas, with a regular hull ship for comparison. I'm pretty sure this is the one that I saw in a documentary about the design. They showed a glass of water sitting on a table in the SWATH ship, not spilling. I'm pretty sure that the glass would go flying in the other ship.

Re:SWATH doesn't require power (1)

DerekLyons (302214) | about 7 months ago | (#44781565)

OTOH, SWATH hulls are more expensive than conventional hulls and offer less volume per displacement ton.

Re:SWATH doesn't require power (1)

SirCowMan (1309199) | about 7 months ago | (#44783035)

SWATH's make nice boats. The tradeoff is in the narrow hulls down to the pontoons - it's limiting not only from a tankage perspective, but also in terms of arranging the driveline and providing sufficient access. They require a wide footprint to provide adequate stability, and like an oil rig, must be very carefully considered for safety when damaged.

Mercury Pots (4, Interesting)

Lev13than (581686) | about 7 months ago | (#44779221)

Reminds me of the chapter in Neal Stephenson's The Confusion (part of The Baroque Cycle [wikipedia.org]). Japanese mercury vendors try to disable the Minerva (an armed merchant vessel) by filling its cargo hold with half-filled pots of mercury, rather than filling them to the brim. The idea is that the sloshing in the hull would resonate with the waves at the entrance to the harbour and slow the ship enough to be captured (or something to that effect). There's a discussion of whether Stephenson got the science correct here [blogspot.ca].

Re:Mercury Pots (0)

Anonymous Coward | about 7 months ago | (#44780367)

Interesting reference to some physics that will hopefully find its way to Myth Busters.

Compressed air?, surely there is a way to do this with some counter weighted system?

Re:Mercury Pots (0)

Anonymous Coward | about 7 months ago | (#44782687)

The water in the tanks is the counterweight. But left to its own, the counterweight would resonate with the ship and only make things worse. With some controls (compressed air) you phase shifts it and cancel out all movement.

A counterweight with a different resonant frequency might work well as a passive dampener, but it would not stop the rocking completely. To make the ship stand still, you need an active system.

Re:Mercury Pots (1)

SirCowMan (1309199) | about 7 months ago | (#44783039)

Rather than weights, gyroscopes are sometimes used.. the ship will be mostly still, there will still be a small bit of motion and if not done right the non-linear response of the dampened vessel can lead to sea-sickness. Also, it will still heave.

Re:Mercury Pots (0)

Anonymous Coward | about 7 months ago | (#44785141)

You might also be interested in nickel ore, which is prone to liquefaction during shipping [bloomberg.com]. The resulting instability is why nickel ore ships represent about 25% of all dry bulk ship losses, despite accounting for only 0.1% of dry bulk cargoes.

INFRINGEMENT!!! (0)

Anonymous Coward | about 7 months ago | (#44779413)

I claim patent infringement. Now give me money so I may pay my lawyers.

Wow! Just like ... (2)

PPH (736903) | about 7 months ago | (#44780155)

... lots of high end yachts.

This has been done for a few years now. Fuel and potable water tanks in the ships sides connected via pipes with computer controlled valves. Some sailboats include pumps to actively move liquid to the windward side tanks to decrease heeling.

It's much older than that... (1)

DerekLyons (302214) | about 7 months ago | (#44780775)

More than just a few years now... try a few decades. (More like a century in fact.) They're called anti-roll tanks [wikipedia.org], and were first used around the turn of the 20th century.

(Naval architecture geek FTW!)

Re:It's much older than that... (0)

Anonymous Coward | about 7 months ago | (#44781443)

But "generating its own waves" seems to indicate an active system, no? The wikipedia article you link says those were investigated in the 1960s, and implies they've never been used practically, so if that's the case, it might be news. (Can't be arsed to RTFA, sorry.)

Re:It's much older than that... (2)

SirCowMan (1309199) | about 7 months ago | (#44782985)

They certainly are used used today and practical, though the are also somewhat dangerous if not operated with due regard to their ability to increase a ships chance of capsize. In addition to the anti-roll tanks in the Wikipedia article, there are also 'heeling tanks' - large ballast tanks with oversized bilge pumps used primarily in icebreakers to rock them as they transit through ice, though they are not intended to offset a rolling motion. For a vessel where motion control is imperative, such as a research vessel, two controlled tanks might be fitted to react to a larger range of ships self-displacement and wave frequencies. This can be in addition to what you're more like to see on a yacht - active fin control - as fins require forward speed to be effective, anti-roll tanks do not. The basics of this concept were hashed out pretty well by the 1960's ... though today's control systems are more advanced, can be predicted (rather than reactive) by monitoring the oceans surface, and the reaction of the tank can be better modelled through CFD programs as there is inevitably structural elements through the duct which affect the tanks operation. Having just read the article, no, this is not news. There are commercial outfits who will provide the entire system, turn-key, if the tanks are accounted for in the vessels design.

Re:Wow! Just like ... (0)

Anonymous Coward | about 7 months ago | (#44782847)

Fuel and potable water tanks in the ships sides connected via pipes with computer controlled valves.

Pah! Haven't these guys learned you shouldn't mix water and fuel?

Re:Wow! Just like ... (1)

SirCowMan (1309199) | about 7 months ago | (#44783059)

In the old days, yes, fuel tanks would be afterwards filled with water and used as ballast, with obvious environmental consequence. There will be a bit of water in ships which use residual fuel, it goes through a seperator before use. Some modern vesssels still mix use fuel and ballast in the same tank to maintain a constant displacement, i.e., naval vessels, though where still done they are seperated by a rubber bladder inside the tank.

How to sink a ship. (2, Interesting)

Anonymous Coward | about 7 months ago | (#44780439)

They had better get it right. When I use to drive a tractor/tanker, if you didn't get your 1st an 2nd gear shifting just right, the chemicals in the tank would shift with such extreme force, that it would almost knock your head off. You can easily hurt your back driving a tanker. I can just see a ship getting the wave out of sink and bursting a hold in the hull.

Re:How to sink a ship. (0)

Anonymous Coward | about 7 months ago | (#44782639)

Uhu. They might achieve resonance and make you extremely seasick, but they're not going to "burst" anything. (Think about the physics for a few seconds, and then slap yourself for even suggesting that.)

Cheaper Solution (0)

Anonymous Coward | about 7 months ago | (#44780475)

Traditionally sailors accomplish this by slowly filling the ships bilge with vomit.

Well known system, with well known dangers. (0)

Anonymous Coward | about 7 months ago | (#44781517)

Yep. These anti-roll or flume tanks have been around for a very long time, both passive systems and active ones like this. Basically they use the free surface effect in reverse by slowing down the sloshing of water in a tank so it counteracts rolling instead of adding to it.

However, if the roll period of the ship and the movement of water in the tank synchronize, you have only second to act before it can roll the ship to a dangerous degree or capsize it outright. They're fitted with dump valves to the port and starboard, just in case...

The more things change (0)

Anonymous Coward | about 7 months ago | (#44785949)

See Den Hartog (1956) 'Mechanical Vibrations" for description of ship stabilization using this method a century ago. It was supplanted by the Sperry system in the 1930s.

Not inner waves. Two actions at work. (2)

advid.net (595837) | about 7 months ago | (#44796207)

This isn't inner waves, but water moving back and forth in a U shaped tank (water is pushed by compressed air on the tops of the U shape, alternatively).
So there's no wave at all in the tank.

I just wonder:

Is the counter-reaction mainly cause by the counter-weight of the water which fills only one side of the U tank, or by the momentum (acceleration) given to the water rolling in the tank ?
In either case, it could be more easily done with some solid weight on rails, with less energy lost (air compression and fluid displacement).

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