Also known as killer waves, rogue waves swell up seemingly out of nowhere and can be eight times higher than the surrounding sea. They can strike in otherwise calm waters with virtually no warning, causing untold devastation even to large ships and ocean liners.
Now, MIT has developed a predictive tool it says can give ships and their crews a two- to three-minute advanced warning, allowing them to shut down essential operations on a ship or offshore platform.
In the past, scientists have approached the problem by trying to simulate every individual wave in a body of water to produce a high-resolution picture of the sea state. It's proven computationally expensive and time-consuming.
In this case, the MIT researchers took a different tack based on their observation that waves sometimes cluster together in a group, rolling through the ocean together. Certain wave groups, they found, end up “focusing” or exchanging energy in a way that eventually leads to a rogue wave.
“These waves really talk to each other,” said Themis Sapsis, the American Bureau of Shipping Career Development assistant professor of mechanical engineering at MIT. “They interact and exchange energy. It’s not just bad luck. It’s the dynamics that create this phenomenon.”
Combining ocean-wave data available from measurements taken by ocean buoys with a nonlinear analysis of the underlying water wave equations, Sapsis' team quantified the range of wave possibilities for a given body of water. They then developed a simpler and faster way to predict which wave groups will evolve into rogue waves.
The resulting tool is based on an algorithm that sifts through data from surrounding waves. Depending on a wave group’s length and height, the algorithm computes a probability that the group will turn into a rogue wave within the next few minutes.
“It’s precise in the sense that it’s telling us very accurately the location and the time that this rare event will happen,” Sapsis said. “We have a range of possibilities, and we can say that this will be a dangerous wave, and you’d better do something.”
A paper describing the tool was published this week in the Journal of Fluid Mechanics.