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| Titel |
Direct measurement of nonlinear dispersion relation for water surface waves |
| VerfasserIn |
Tore Magnus Arnesen Taklo, Karsten Trulsen, Harald Elias Krogstad, Odin Gramstad, José Carlos Nieto Borge, Atle Jensen |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079291
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| Zusammenfassung |
| The linear dispersion relation for water surface waves is often taken for granted for the
interpretation of wave measurements. High-resolution spatiotemporal measurements
suitable for direct validation of the linear dispersion relation are on the other hand
rarely available. While the imaging of the ocean surface with nautical radar does
provide the desired spatiotemporal coverage, the interpretation of the radar images
currently depends on the linear dispersion relation as a prerequisite, (Nieto Borge et al.,
2004).
Krogstad & Trulsen (2010) carried out numerical simulations with the nonlinear
Schrödinger equation and its generalizations demonstrating that the nonlinear evolution of
wave fields may render the linear dispersion relation inadequate for proper interpretation of
observations, the reason being that the necessary domain of simultaneous coverage
in space and time would allow significant nonlinear evolution. They found that
components above the spectral peak can have larger phase and group velocities than
anticipated by linear theory, and that the spectrum does not maintain a thin dispersion
surface.
We have run laboratory experiments and accurate numerical simulations designed to have
sufficient resolution in space and time to deduce the dispersion relation directly. For a
JONSWAP spectrum we find that the linear dispersion relation can be appropriate for the
interpretation of spatiotemporal measurements. For a Gaussian spectrum with narrower
bandwidth we find that the dynamic nonlinear evolution in space and time causes the directly
measured dispersion relation to deviate from the linear dispersion surface in good agreement
with our previous numerical predictions.
This work has been supported by RCN grant 214556/F20.
Krogstad, H. E. & Trulsen, K. (2010) Interpretations and observations of ocean wave
spectra. Ocean Dynamics 60:973-991.
Nieto Borge, J. C., Rodríguez, G., Hessner, K., Izquierdo, P. (2004) Inversion of marine
radar images for surface wave analysis. J. Atmos. Ocean. Tech. 21:1291-1300. |
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