News coverage:
http://news.yahoo.com/s/livescience/20110618/sc_livescience/freakwavescouldspringfromclashofwavepatterns
Towering walls of water blamed for taking out huge ships and helicopters alike have remained a mystery. What would cause a single wave among many others to reach 100 feet high? New computer simulations suggest that a freak, or rogue, wave may result when two wave systems meet while traveling perpendicular to each other.
“No one really has an adequate explanation as to why you would get freak waves in the middle of the ocean,” study researcher Thomas Adcock, of the University of Oxford, told LiveScience. “Our real objective in studying these is eventually we would say, ‘This particular sea state is particularly susceptible to freak waves.’ “
A rogue wave is defined as any open-ocean wave that is abnormally larger than the waves around it.
[...]
The study was published today (June 14) in the journal Proceedings of the Royal Society A: Mathematical, Physical & Engineering Sciences.
Here’s a link to the paper’s abstract:
http://rspa.royalsocietypublishing.org/content/early/2011/06/09/rspa.2011.0049.abstract
Did the Draupner wave occur in a crossing sea?
T. A. A. Adcock 1,*,
P. H. Taylor 1,
S. Yan 2,
Q. W. Ma 2 and
P. A. E. M. Janssen 3
1 Department of Engineering Science, University of Oxford, Oxford, UK
2 School of Engineering and Mathematical Sciences, City University, London, UK
3 European Centre for Medium-Range Weather Forecasts, Reading, UK
*.Author for correspondence (thomas.adcock{at}st-peters.oxon.org).
Abstract
The ‘New Year Wave’ was recorded at the Draupner platform in the North Sea and is a rare high-quality measurement of a ‘freak’ or ‘rogue’ wave. The wave has been the subject of much interest and numerous studies. Despite this, the event has still not been satisfactorily explained. One piece of information that was not directly measured at the platform, but which is vital to understanding the nonlinear dynamics is the wave’s directional spreading. This paper investigates the directionality of the Draupner wave and concludes it might have resulted from two wave-groups crossing, whose mean wave directions were separated by about 90 [degrees] or more. This result has been deduced from a set-up of the low-frequency second-order difference waves under the giant wave, which can be explained only if two wave systems are propagating at such an angle. To check whether second-order theory is satisfactory for such a highly nonlinear event, we have run numerical simulations using a fully nonlinear potential flow solver, which confirm the conclusion deduced from the second-order theory. This is backed up by a hindcast from European Centre for Medium-Range Weather Forecasts that shows swell waves propagating at approximately 80 [degrees] to the wind sea. Other evidence that supports our conclusion are the measured forces on the structure, the magnitude of the second-order sum waves and some other instances of freak waves occurring in crossing sea states.
Seasteads and a location search for them may want to avoid places with a tendency towards crossing seas, if it reduces the chances of rogue waves there.
Seasteader- 1 year, 11 months ago.
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