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Rogue Wave Behavior Affected by Crossing Angle

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By MarEx 2018-01-09 09:04:45

New understanding of rogue indicate that they increase in size when they are produced by two sets of waves crossing at a particular angle, a study has found. 

Rogue waves are unusually large surface waves that occur in the ocean. 

The increase related to crossing angle, which has been demonstrated in an experiment for the first time, is believed to have played a part in producing a 25-meter wave, known as the Draupner wave, which struck a North Sea oil platform in 1995.

Experiments carried out at the University of Edinburgh have shown for the first time how large waves are affected by the angle at which they intersect. Researchers used a 25-meter circular testing tank to show that when waves intersect at an angle greater than approximately 60 degrees, they cause the surface level of the ocean to rise. This adds to the overall height of the combined wave that results.

Last year, University of Miami scientist Professor Mark Donelan demonstrated that rogue waves aren’t as rare as previously thought. He captured new information about extreme waves as a result of information gained when one of the steepest ever recorded passed by the North Sea Ekofisk platforms in the early morning hours of November 9, 2007.

The Andrea wave passed by a four-point square array of ocean sensors designed by the researchers to measure the wavelength, direction, amplitude and frequency of waves at the ocean surface. Using the information from the sensors they found that rogue waves are not rare as previously thought and occur roughly twice daily at any given location in a storm. The findings showed that the steeper the waves are, the less frequent their occurrence.

In 2016, a researcher from Aalto University in Finland developed a laboratory method for generating rogue waves under realistic oceanic conditions. Also that year, a prediction tool was developed by MIT engineers that may give sailors a two to three minute warning of an incoming rogue wave, hopefully providing them with enough time to shut down essential operations on a ship or offshore platform. The tool, in the form of an algorithm, sifts through data from surrounding waves to spot clusters of waves that may develop into a rogue wave. 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.