Rogue wave theory to save ships

Rogue wave theory to save ships

Physicists have found an explanation for rogue waves in the ocean and hope their theory will lead to devices to warn ships and save lives.

"A device on the mast of a ship analysing the surface of the sea could perhaps give a minute's warning that a rogue wave is developing," said Professor Nail Akhmediev, leader of the research at the Research School of Physics and Engineering.

"Even seconds could be enough to save lives."

Rogue waves develop apparently out of nowhere over the course of about a minute and grow to as much as 40 metres in height before disappearing as quickly as they appeared.

Ships unlucky enough to be where appear can capsize or be seriously damaged, as happened in the Mediterranean Sea to the Cypriot ship Louis Majesty, which was struck by a rogue wave in 2010 that left two passengers dead and fourteen injured.

The research by Professor Akhmediev and the team at the ANU Research School of Physics and Engineering, Dr Adrian Ankiewich and PhD student Amdad Chowdury, is published in Proceedings of Royal Society A.

Professor Akhmediev said that there are about 10 rogue waves in the world's oceans at any moment.

"Data from buoys and satellites around the world is already being collected and analysed. Combined with observations of the surrounding ocean from the ship this would give enough information to predict rogue waves," said Professor Akhmediev.

The theory may also explain that wash away people from beaches, as the rogue waves can sometimes transform into travelling waves known as solitons, that travel through the ocean like mini-tsunamis until they hit the coastline.

Rogue wave theory to save ships

Professor Akhmediev's theory also applies to other chaotic phenomena such as light travelling in optical fibres, atoms trapped in a Bose-Einstein condensate and the ionosphere in the upper atmosphere.

The rogue wave is a special solution of the non-linear Schrodinger equation which is localised in time and space. The solutions were derived by adding terms to cover dispersion to the non-linear Schrodinger equation, forming the Hirota equations.

Professor Akhmediev said that he next plans to add more terms to account for the influence of the wind on waves.


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More information: "General high-order rogue waves and their dynamics in the nonlinear Schrödinger equation." Proc. R. Soc. A 2012 468 1716-1740; DOI: 10.1098/rspa.2011.0640
Citation: Rogue wave theory to save ships (2015, July 29) retrieved 18 July 2019 from https://phys.org/news/2015-07-rogue-theory-ships.html
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Jul 29, 2015
Pretty cool if they can detect it in advance. I wonder what a ship can do in a minute, though, to escape it.

Jul 29, 2015
Point up into the wave or directly away from it. Even a big ship can change its heading substantially in a minute if it is moving at transit speeds, and taking a big wave head- or stern-on instead of broadside can make the difference between a bit of a roller-coaster ride and a VERY bad day indeed.

Er, trolls: cut me some slack on this one, I've driven everything from a sailing dinghy to an aircraft carrier.

Jul 29, 2015
Point up into the wave or directly away from it. Even a big ship can change its heading substantially in a minute if it is moving at transit speeds, and taking a big wave head- or stern-on instead of broadside can make the difference between a bit of a roller-coaster ride and a VERY bad day indeed.

Er, trolls: cut me some slack on this one, I've driven everything from a sailing dinghy to an aircraft carrier.


ah but did you ever close the barn doors on an Iowa class battleship?

Jul 29, 2015
So many experienced and educated people here...wow!

They can clear the decks.

Jul 29, 2015
ah but did you ever close the barn doors on an Iowa class battleship?


HAH! Now that's an old-guy question...

On the Iowa-class BB you'd have to turn two rudders against the other two AND take them all the way to the stops (inboard to the skegs) in order to accomplish that. Not sure whether you could pull that one off from the pilot house--certainly never had independent rudder control from the bridge on any of MY ships--so my guess is that anybody who actually DID that (as opposed to issuing the order from the bridge) probably did it manually from after steering.

Which is salty as hell and beats any true story I ever told. Dang.

Jul 29, 2015
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Jul 30, 2015
Point up into the wave or directly away from it.

I wonder if that works for large ships (container ships or oil tankers) from a structural point of view. At the very peak of the wave the bow and stern are 'in the air'. IIRC then that's the best way to break a ship.
Going side-on is certainly a recipe for disaster. But there may be a sweet spot regarding the realtive heading?
Would be interesting to model this via FEM and see what the best course of action is.

Jul 30, 2015
This comment has been removed by a moderator.

Jul 30, 2015
This comment has been removed by a moderator.

Jul 30, 2015
This comment has been removed by a moderator.

Jul 30, 2015
This comment has been removed by a moderator.

Jul 30, 2015
I wonder if that works for large ships (container ships or oil tankers) from a structural point of view. At the very peak of the wave the bow and stern are 'in the air'. IIRC then that's the best way to break a ship.


Yah that situation is called "hogging" (as opposed to "sagging", with a wave peak at each end and midships in the trough). Definitely to be avoided, but takes a pretty big wave to hog a big ship & break its back. That's what torpedos are for. :)

You aren't wrong, though. The most comfortable way to take a really big wave is actually a couple of points off the bow or stern. You get more control and a softer landing.

Jul 31, 2015
Idiots that get their jollies off buggering their own arse will not cease and desist until you ignore them and do not even mention the trolls. Just think about it. You suffer from mental illness and you sit around buggering yourself all day, waiting for a chance to spew because that's the only thing that makes you feel alive. We *owe* it to them to extinguish the behavior.

I'm going to use my new data to give the two on here a bit of a surprise. I'd rather beat the living shit out of them, but as that's not practical one thinks some trolling where they aren't anonymous cowards is in order. Rule #1 of trolling: don't do it on a site with 11 tracking cookies and poor data security. I know every site those two have been to in 6 months. lol, Denglish, what's with NAMBLA? I think even they would cringe at the sight of you. Docile, "crush video" sites are a symptom of a deeply disturbed mind. Yeah, we knew, but that's surprising even by your standards.

Jul 31, 2015
Denglish, what's with NAMBLA?


Idiots that get their jollies off buggering their own arse will not cease and desist until you ignore them


Apropos

KBK
Aug 03, 2015
Idiots that get their jollies off buggering their own arse will not cease and desist until you ignore them and do not even mention the trolls. Just think about it. You suffer from mental illness and you sit around buggering yourself all day, waiting for a chance to spew because that's the only thing that makes you feel alive. We *owe* it to them to extinguish the behavior. (cut)


Actually, no. Not at all. People should spew, as that how things get shared, how we advance. Some may not like it, this out with the old (pain) in with the new (confusion).

All the greats and not greats share(d) and blather(ed) on. Incessantly.

It is a very simple thing: life.. is motion and change. Comfort and routine --- is death.

KBK
Aug 03, 2015
By the way, Docile. Very good. Spot on. You're getting it.....

As above, so below. Scaling follows through in all things. (global scaling theory)

KBK
Aug 03, 2015
To add, the man who 'created' global scaling theory was charged with..whatever. I don't know the specifics.

However, conspiracy and secretive control mechanisms are alive and well in all areas, most especially in academia and science, which has the power to shift entire planets as much -or more than- religion or war.

Ignorance and a childlike mental state, or a desire to shill to that mentality of crowd (maintenance of ignorance and control)....would be the origin of any disbelief or verbal rancor thrown at this comment.

Aug 03, 2015
Definitely to be avoided, but takes a pretty big wave to hog a big ship & break its back. That's what torpedos are for. :)

Heh...that's exactly where I got the idea.

a couple of points off the bow

Could you explain what this means? I've heard this nautical term before (I guess it means a few degrees off to the side?)...but what do 'points' exactly refer to in this context?
(I just love trivia like that)

Aug 03, 2015
"but what do 'points' exactly refer to in this context?"
Compass points, you guessed right :) You're looking to (sort of) slide up and over, rather than crashing straight through, remember, both ship and wave are moving.
Never sailed anything bigger than a 40' yacht, but it's a technique that scales from dinghy to battleship I guess.

Aug 11, 2015
A "point" on a compass rose is just one of a number of even divisions of arc: https://en.wikipe..._compass

Different compasses have different numbers of points, but 16 or 32 is typical. So "a couple of points" is a hand-wavy expression, equivalent to "a few degrees".

While you can generally set a ship's course to within a degree or so of a particular heading and keep it there, maneuvering a big ship in real time just isn't that precise. So while I could issue the order "come right 17 degrees" in order to take a wave just right, in practice by the time the helmsman stabilizes on that course the wave would be long past. So I'm more likely just to tell him to ease the helm a couple of points and let him use his judgement from there.

Aug 11, 2015
Never sailed anything bigger than a 40' yacht, but it's a technique that scales from dinghy to battleship I guess.


It does... but with some surprising differences. Your typical 40' yacht has got a heavy keel slung well below its center of mass and not much mass above decks. Even with a full sail plan this configuration results in very "stiff" handling: when the boat rolls, it tries very hard to right itself. Even in heavy seas, the balance of forces between the keel and the sails result in a remarkable degree of stability.

A warship, on the other hand, carries heavy weapons and sensor systems above the main decks that tend to make it far more top heavy and liable to roll.

The bottom line: 25' seas that might cause a bit of a clench aboard a 50' racing yacht will injure people and break things aboard a 450' frigate. Been there, NOT an experience I'd care to repeat.

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