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Rogue waves

bentilly.blogspot.com

53 pointsbtilly9 comments

If anyone is interested in a more tractable experimental platform for the study of this effect - it has also been observed for light propagating in an optical fiber. There is an interesting analogy between the nonlinear wave propagation effects believed to be responsible for ocean rogue waves and those responsible for optical effects like supercontinuum generation.

Here's a recent nature paper where researchers observed "optical rogue waves" in the light propagating through a microstructured optical fiber.

http://www.ee.ucla.edu/~oecs/comp_pub/intr_opt/Optics154.pdf

This follows the pattern of solitons - they were first observed in a boat canal, and later found in optics.

So wait a minute... you're telling me that:

1) Ships are built to withstand normal waves, and have a high likelihood of sinking if hit by a rogue wave.

2) Rogue waves are a regular feature of the ocean, frequent enough that a number of ships every year will be hit by rogue waves.

3) These rogue waves can effectively occur anywhere in the ocean.

4) Despite this, commercial liners, cruise ships, tankers, etc, continue to go out to sea, taking sometimes hundreds of people with them.

Is this basically saying that this common mode of transportation is inherently unsafe and to be avoided? It's one thing to say that "shit happens, and if something goes wrong with the plane, you're fucked", and another altogether to say "we know that this will happen, for sure, one out of X times, no matter how well we may prepare, and it will most likely sink the ship". X may be rather large, but the point is it could be prepared against, but it's not.

These wave sound like Black Swan events - real events whose probabilities don't fit our current understanding and models. On one hand of course it's unsafe to send ships out on the ocean, but on the other hand, there are tens (hundreds?) of thousands of ships at sea every day and these waves weren't even measured until 1995. Right now they need to figure out X and then shipbuilding and insuring will adjust accordingly.

from what I've heard (I cannot remember where, but it's likely some discovery channel gumph about the "10 000 year wave") it's the best kept maritime secret that one large boat a month goes under...

... keeping in mind that these ships are most likely shipping containers, and that all things involved are likely covered by some insurance policy that has evolved over hundreds of years of industrial experience (where rogue waves need not be known or even measured to be a factor). I don't think it's too unreasonable to carry on regardless, however misguided. I've always found it strange though.... especially since I've always wanted to do the banana boat "cruise" thing!

That's not unlike the situation with airliners and downbursts in the 70s and 80s. A not-uncommon atmospheric effect, rumored, then known, then studied, led to one out of X planes falling out of the sky.

But we still put people on planes.

The unsettling difference, that you hit on, is: when Fujita finally got through to the FAA, planes and pilots were quickly brought up to speed; but the sea transport industry has seen the rogue wave research and doesn't seem to be particularly interested in changing anything.

Probably because they ship many more goods than people, and goods don't care if they drown, so long as their owners' insurance claims are paid.

> "we know that this will happen, for sure, one out of X times, no matter how well we may prepare, and it will most likely sink the ship". X may be rather large, but the point is it could be prepared against, but it's not.

The cost of "prepared against" matters as does the value of X.

Some risks are worth protecting against while others aren't. While the right answer for a given risk may change over time, the latter group is never empty.

Of course, you may value your safety differently than the folks making that call for ships. If so, ....

Can a ship be built to withstand a 100 foot rogue wave? I don't know if it's even possible. It's probably possible to design a ship to take 100 feet of water at the bow, but what happens if you have to design for a wave hitting the stern or the sides as well? Do you end up with a giant brick of steel that doesn't even float? Then throw on top the economics where the vast majority of ships won't encounter a wave of that magnitude in their lifetimes.

The solution probably isn't better ships, but better mapping of wave conditions and routing around more dangerous areas.

The ship doesn't need to withstand the wave without any damage - that would be unnecessarily expensive. But they should at least be designed to withstand such a wave without sinking.

If I climb on a ship and you tell me "well, there's a 1 in 100'000 chance that we'll be hit by a freak wave and then it's quite likely that everyone on board will die, since the ship will be broken in half and sink", that's a very different thing to say than "well, there's a 1 in 100'000 chance that we'll be hit by a freak wave, and then the ship will sustain severe damage but should be able to limp back to shore or at least float long enough for a rescue."

The difference between those two scenarios is probably less expensive than you think.

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