# Waves

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WhisprWave breakwater

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

## Rogue Waves

Rogue waves are unusually tall waves that appear spontaneously on the open ocean. Their source remains somewhat of a mystery, but rogue waves are a topic of significant scientific and mathematical study due to the damage they cause to ships, platforms, etc. Rogue waves are capable of sinking, and have sunken even very large ships.

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". The article summarizes both Linear Addition and Nonlinear Focusing theories and describes a new way to combine both into a new theory.

The Dashews describe a Linear Addition theory:

"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.
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