The ongoing mystery of the ocean’s towering rogue waves

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The ongoing mystery of the ocean’s towering rogue waves

At 3:00 p.m. on New Year’s Day in 1995, work stopped on the deck of the Norwegian Draupner oil platform, which stood isolated out in the middle of the tempestuous North Sea. The wind had grown too strong, the waves roiled below, and it was no longer safe to be outside. 

But one wave dwarfed the others. It measured 84-feet tall — about two and a half times the height of a telephone pole — and was thereafter named the “Draupner wave.” Fortunately, the monstrous swell didn’t reach the platform’s deck.

The Draupner wave was the first scientific evidence of a rare rogue or freak wave, which is a wave that appears suddenly and measures at least twice as tall as the surrounding waves. These fleeting, colossal phenomena are thought to be possible culprits for the still-unexplained sinking of ships in the open ocean. 

While there’s still considerable uncertainty about how rogue waves form, a team of engineering scientists has successfully simulated a way that freak waves can suddenly rise from the sea. The researchers recreated a (smaller version) of a Draupner wave in a simulation pool, and published their research in the Journal of Fluid Mechanics

“There’s a rather heated debate on the physical mechanisms of how these things form,” Mark McAllister, a mechanical engineer at the University of Oxford and coauthor of the research, said. “We’ve shown the conditions that can support such a wave.”

Left: Simulated wave. Right: Hokusai’s “Great Wave” (early 1830s).

Image: University of Oxford/The University of Edinburgh

This simulation, achieved at The University of Edinburgh’s 82-foot diameter test tank — which is designed to create real ocean conditions — proved that when a series of waves cross each other at large angles (around 120 degrees), a freak wave will form. 

“It’s an important piece of the puzzle,” Günter Steinmeyer, a physicist at Germany’s Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy who has researched rogue waves, said.

Still, he emphasized that there’s still much we don’t know about these little-seen waves, even over two decades after the famous Draupner event.

“Roughly 20 years later we firmly believe they exist but there are so many explanations around,” said Steinmeyer, who had no role in the study. “They are so rare.”

“If you ask three scientists in the field you will probably hear four different stories, and everybody is sure that all other explanations are completely wrong,” he added.

To create a Draupner, the engineers spent about two days sending waves into one another at varying angles, until they found the right combination. The wave looked a lot like the famous woodblock print “The Great Wave of Kanagawa” from the early 1830s by artist Hokusai. 

“The similarity to Hokusai’s Great Wave was purely coincidental, but a very nice surprise,” Samuel Draycott, an engineer at The University of Edinburgh and a study coauthor, said over email.

“Only a few months later did I read theories that Hokusai’s great wave may actually depict a so-called rogue wave,” Draycott added.

Freak waves have been reported in both the open ocean and near coastlines, Draycott said. Accordingly, understanding when a rogue wave might arise may help seafarers or people working at sea know when conditions are ripe for a rogue, such as two storms approaching from different angles. 

The simulated Draupner wave, about 1-meter high.

The simulated Draupner wave, about 1-meter high.

Image: UNIVERSITY OF OXFORD/THE UNIVERSITY OF EDINBURGH

 

“There are theories that say it’s random,” said McAllister. “And others say that if you have specific conditions, the waves will grow in height.”

Though, there’s likely still a lot of chance at play with any rogue wave, noted Steinmeyer.

The weather conditions have to be right (perhaps stormy). Waves coming from different directions also have to collide at precisely the right time, and the right angle, just like they did beside the Draupner platform.

“Statistically, it’s a quite small number,” said Steinmeyer. Though, he noted that some ship captains who have been at sea for decades have reported spotting huge Draupner waves. 

The 1995 Draupner wave, at least, left the workers hunkered down amid the stormy North Sea, but unscathed.

“Luckily the platform was high enough so the wave didn’t hit the deck,” said McAllister. “Had it been lower it could have been quite catastrophic.”

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