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The Grand Unified Theory of Rogue Waves
- gshubert17 7y ago> [a better model] paving the way for machinery that could, for instance, scan the ocean and notify ship captains that they face a 13% chance of running into a 30-meter wave in the next 15 minutes. What sorts of actions would captains take under these circumstances? Rogue waves are so large and powerful--would any action be enough to prevent losing a ship?
- eloff 7y agoYou'd want to orient the ship to hit it bow first probably, rather than on the side where it could roll or punch a hole in the ship. But what Captain in a serious storm is not going bow first through the waves anyway? I don't know much about the industry, so that's an honest question - maybe deadlines and route optimization still plays a role and they will often sail at an angle to the waves, I doubt they would ever sail near 90 degrees in any case, but maybe you could change a 30 degree angle to closer to 0 if you had warning.
- i_am_proteus 7y agoIt's absolutely normal to steam with little regard to wave direction in mild seas. Merchant ships typically follow great circle routes with as little deviation as possible.
- eloff 7y agoRight, but in a serious storm?
- mark-r 7y agoI think the point of a rogue wave is that it can form even when there's not a storm. They seemingly come out of nowhere.
- eloff 7y agoNot really, they're still proportional to the average wave height. So while you could always be at risk for rogue waves, the sea has to be quite rough before a large vessel need be worried about them.
- mark-r 7y agoI didn't see anything in the article that implied the rogue waves were proportional to the average. In fact the thing that makes them rogue is that they are many standard deviations away from the average.
- eloff 7y agoThis is not the first article I've read on the subject, it's my understanding that rogue waves are built from regular waves, therefore they're proportional - just many standard deviations away as you say. You can get a 20 meter wave in the midst of 10 meter waves, but you're not going to find that in 2 meter waves, rounded to an appropriate number of decimal places.
- gamblor956 7y agoThe whole point of the article is that rogue waves aren't just built from regular waves syncing together...
- 7y ago
- slavik81 7y agoIf the wave is big enough, bow-first won't save you. If you go over the wave, half your ship ends up cantilevered over the peak. A ship isn't built to hold half its weight in the air like that. It will break. If you go through the wave, the upper decks get hit by a wall of water. The windows blow out, the bridge is destroyed, the computers are toast and the ship is swamped.
- HenryKissinger 7y agoForce shields it is then.
- eloff 7y agoAgreed, that if the wave is big enough you're toast anyway, but bow-first still gives your best chance as I understand it. So if you had warning you'd want to get your crew into less vulnerable positions where they can evac more easily, and ensure you're facing bow-first into the waves.
- irrational 7y agoAll that is left is to go under the wave.
- gamegoblin 7y agoFWIW, this is exactly what surfers do ("duck diving").
- echelon 7y agoWhy don't we design submersible container ships? Are the energy costs of displacement while moving entirely underwater too expensive?
- learn_more 7y agoPerhaps the density of the cargo is, on average, too low. The amount of ballast needed would make it impractical.
- 7y ago
- btilly 7y agoYou'd want to orient the ship to hit it bow first probably, rather than on the side where it could roll or punch a hole in the ship. But what Captain in a serious storm is not going bow first through the waves anyway? Hitting the swell bow first will not necessarily help you. See https://www.youtube.com/watch?v=A2KqofR05TE https://www.youtube.com/watch?v=A2KqofR05TE for a video of a boat actually hit by a rogue wave. They are riding the swell correctly - but the wave hits from the side. Note that a swell and a current are known conditions that make rogue waves more likely. And it is not uncommon for rogue waves to be moving in a different direction than the swell.
- eloff 7y agoSomeone else also commented that it won't save you if the wave is big enough. I'm not contesting that. I'm just saying that gives you your best chance.
- btilly 7y agoYou ignored the point that rogue waves often move in a different direction than the swell. So orienting by the swell doesn't help you with a rogue wave.
- eloff 7y agoI'm not sure if I just missed it because I was busy, or if you edited the comment afterwards, but that's a good point. If the rogue wave comes from a different direction then orienting with the rest of the waves won't save you. In that case maybe if you could get some warning in time it could help. You might not be able to get to 90 degrees, but maybe you won't get caught flat out on the side either. Still even that may not be enough to save you. The ship that went down in the North Atlantic was hit front on and sunk.
- emmelaich 7y agoIn the sort of seas that produce rogue waves, the direction of the rogue wave is also less predictable.
- deleted 7y ago[deleted]
- tkahnoski 7y agoBatten down the hatches. Or maybe a herd strength thing where one ship detects and can send out an alert for others to redirect around the path.
- andrewflnr 7y agoYou could make sure all your people are awake and ready to get in the lifeboats if the ship breaks up. Definitely make sure no one is way down in the hold where they'll drown before they get on deck.
- jschwartzi 7y agoDoes this have anything to do with Markov Chains? Because it's smelling like that type of problem. The verbiage in the article is a little too "wanky" for me to tell.
- mturmon 7y agoIf you had to reach into your bag of probability concepts to pick the most closely related one, it would be "Large Deviations", which comes up for engineers in the context of information theory. Basically, as explained in the article, many kinds of rare events (like, averages attaining values far from the population mean) can be characterized without knowing a lot of problem-specific details. For instance, if the typical value for an average of 1000 positive numbers is 10, and you want to know the chance of an outcome greater than 100 (a "large deviation"), you can pretty much just calculate the chance of the outcomes very near 100, without caring about 120 or greater. That is, it turns out that the larger outliers carry very little probability, although that's not obvious. This phenomenon comes up a lot and goes by several names. It was known to Laplace and there's an approximation used commonly in that area bearing his name. It's also related to the notion in information theory of the "typical set". Similarly, you can, in some ways, characterize the realizations that cause these extreme values. (As opposed to just computing their probabilities.) For instance, if I remember right, the typical realization that gives rise to a large average has just a few larger-than-expected values and a vast majority of about-average values, rather than every value being slightly too large. This is a highly general property.
- ishtanbul 7y agothis seems like an insurance problem, rather than a technical one. rogue waves appear to be rare enough that spending money on prediction or detection might outweigh the cost of simply insuring against catastrophic loss
- HeyLaughingBoy 7y agoTell that to the people on the ship that it happens to! Granted, it's usually survivable. Decades ago a friend of mine on a containership experienced a rogue wave with no more harm than being terrified by "either the last thing I was ever going to see or the most majestic thing I'd ever see" but it doesn't always end that way.
- btilly 7y agoIt is both. Ships used to be built to the largest waves that were conceivable. We underestimated the forces in a rogue wave by a factor of more than 5. Ships today are built stronger, we are careful about seas where rogue waves are more common, and insurance now knows to take rogue waves into account in their policies. Better predictions as well would be good.
- Ono-Sendai 7y agoIf anyone wants to see a clear video of a rogue wave in the wild: https://www.youtube.com/watch?v=uK_4V3zqAvg https://www.youtube.com/watch?v=uK_4V3zqAvg
- killjoywashere 7y agoI wish people walking around with personal video cameras in their pockets were a thing at the turn of the millennium. I was on the bridge of an aircraft carrier going around Cape Horn, taking green water over the bow. Not once, but many, many times.