Waves

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Describing Waves

During the service life of an offshore structure, it will experience a huge number of waves, from very small wavelets to possibly giant waves. A practical way to describe these unceasingly changing waves

is to divide them into various categories (sea states), and use short-term wave statistics to depict each sea state and long-term wave statistics, usually in the form of a wave scatter diagram and rosette, to delineate the rate at which a sea state occurs.

In a similar way, there are two levels in the description of wave directionality, i.e., wave directional spectrum or wave spreading for short-term, and wave rosette for long-term, respectively. 

See Section 3 of ABS GUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR FLOATING OFFSHORE STRUCTURES . 2005 for further discussion of Wave measurement.

Map of wave heights: https://static1.squarespace.com/static/57070436f699bbcfa154423d/t/583b353b725e257a97db2cfe/1480275484044/?format=750w

Rogue Waves

"There really is no such thing as a rogue wave. These larger than normal seas are the result of two wave trains coinciding at just the right moment for their energy to combine. When this happens the higher-than-normal crest is exposed to more wind force and absorbs additional energy. And if the wave happens to be unstable and breaks - because the rotating particles within the wave can no longer make it over the top - there will be a large mass of water falling downhill."

From "Surviving the Storm" by Steve & Linda Dashew, page 241.

Rogue waves are a topic of major study due to the damage they cause to ships, platforms, etc. Recent research finds new ways to model and possibly predict them as described in a Quanta Magazine article from February 2020 titled "The Grand Unified Theory of Rogue Waves"].

See also



Ocean Environment
General · Waves · Sea state · Currents · Wind · Politics · Piracy · Biofouling