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| Titel |
Modulation depth and breaking strength for deep-water wave groups. |
| VerfasserIn |
Alina Galchenko, Alexander Babanin, Dmitry Chalikov, Ian Young, Tai-Wen Hsu |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250031743
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| Zusammenfassung |
| Progression of nonlinear wave groups to breaking was studied numerically and
experimentally. Evolution of such wave group parameters as distance to breaking and
modulation depth was described. The wave modulation depth R is a height ratio
of the highest Hh and the lowest Hl waves in the group: R = Hh-Hl (Babanin
et al. 2009). This parameter, together with distance to breaking, was studied by
means of the fully-nonlinear Chalikov-Sheinin (CS) model (Chalikov and Sheinin,
2005). Subsequent experiment demonstrated a good qualitative agreement with the
numerical results. In the present study, both in numerical simulations and laboratory
experiments, a wave group was initially generated as a superposition of two waves with
primary and secondary wave steepnesses and close wave numbers, and allowed
to evolve. It was shown that the modulation depth decreases as a function of the
primary wave steepness, that distance to breaking also decreases with primary wave
steepness, but grows as a function of the ratio of the primary and secondary wave
steepnesses.
Babanin et al (2007) investigated initially monochromatic wave trains, where the side
bands necessary for the Benjamin-Feir (BF) modulation (Benjamin and Feir 1967) grew
naturally from the background noise. These monochromatic waves experienced
self-modulation, and developed into strongly modulated wave groups. In the subsequent
study, Babanin et al. (2009) noticed that the depth of this modulation is essentially affected
by the wind and, in turn, influences the breaking severity. In the present study, in
order to achieve different modulation depths and investigate this connection of
wave groups with the breaking strength, but to avoid the complicating action of the
wind, the wave groups were initially imposed. It was shown that energy loss, i.e.
the breaking severity is a function of modulation depth. Energy loss grows with
modulation depth up to a certain level of the latter. It was also found that breaking
probability for wave groups with modulation depth R |
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