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Famous Japanese "Freak Wave" recreated in the lab



  Famous Japanese

The famous Japanese artist Katsushika Hokusai, known as "Under the Wave before Kanagawa" and "The Great Wave", is considered a so-called Freak Wave. 19659003] Photo credits: Katsushika Hokusai; Henry L. Phillips Collection, Estate of Henry L. Phillips, 1

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It takes a perfect storm to create an unusual wave, a water wall that is so unpredictable and colossal that it can easily destroy and sink ships a new study.

Take, for example, the Draupner Freak Wave, which arrived on January 1, 1995 near the Draupner oil platform off the coast of Norway. This wave reached an incredible height of 84 feet (25.6 meters), or about the height of four adult giraffes stacked on top of each other. Another famous rogue wave is portrayed by Japanese artist Katsushika Hokusai in his 19th century woodcut entitled "The Great Wave," which shows a tremendous rise in water moments from an inevitable crash.

To find out why these unusual waves are so suddenly and without warning, an international team of researchers from England, Scotland and Australia reproduced a scaled summit of the Draupner wave in a laboratory tank. [In Photos: Check Out These Monster Waves]

The team has successfully decoded the recipe of the rogue wave: it only needs two smaller wave groups that intersect at an angle of about 120 degrees, they found.

  A rogue wave breaks, as does Véronique Sarano in the Southern Ocean.

A breakwater wave as seen by Véronique Sarano in the Southern Ocean.

Credit: Copyright V. Sarano

The discovery shifts scientists' understanding of unusual waves "from mere folklore to a credible phenomenon in the real world," said study lead investigator Mark McAllister at the Department of Engineering Science at the University of Oxford in England, said in a statement. "By restoring the Draupner wave in the lab, we have come one step closer to understanding the possible mechanisms of this phenomenon."

When sea waves break under typical circumstances, the liquid velocity (the velocity and direction of the water) increases. The tip of the wave, called the crest, exceeds the speed of the tip itself, McAllister said in an email to Live Science , This causes the water in the crown to overtake the shaft and then break off when the shaft breaks.

However, when waves intersect at a large angle (120 degrees in this case), the wave breaking behavior changes. As waves criss-cross, the horizontal fluid velocity under the wave crest is removed, and the resulting wave can get bigger and bigger without falling. "So breaking does not break anymore and there is a jet-like breaking up, as illustrated in our video [see below]and apparently this second way of breaking does not limit the wave height in the same way," McAllister said. [19659005] In other words, when waves intersect at large angles, they can produce monster waves like the Draupner Freak Wave and Hokusai's Great Wave.

Wave groups do not necessarily have to meet at an exact angle of 120 degrees to become dishonest.

"In the case of the Draupner wave, the angle of 120 degrees was required to support such a wave," McAllister said. "More generally, any intersection in the oceans will support steeper waves."

The finding illustrates "a previously unobserved wave breaking behavior that differs significantly from the current state of the art on the waves of the oceans." The lead author of the study, TS van den Bremer, associate professor at the Faculty of Engineering at Oxford University, said in the statement.

The team hopes that their work will form the basis for future studies They help scientists Predicting these potentially catastrophic waves, they said.

The wet and wild animal experiments were conducted at the University of Edinburgh's FloWave Ocean Energy Research facility.

  The Laboratory Rehabilitation of the Draupner Wave.

The Renewal of the Draupner Wave in the Laboratory.

Credit: McAllister, ML et al., J. Fluid Mech. (2019); CC BY 4.0

"The FloWave Ocean Energy Research Facility is a circular combined wave-flow basin with the entire circumference attached Wave makers, "said Sam Draycott, a research associate at the University of Edinburgh's School of Engineering statement This ability enables the generation of waves from all directions. This has allowed us to experimentally recover the complex directional wave conditions that we believe are associated with the Draupner wave event. "

The study will be published on February 10, issue of the Journal of Fluid Mechanics.

Originally published on Live Science .


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