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| Titel |
Simulations of nonlinear harmonic generation by an internal wave beam incident on a pycnocline |
| VerfasserIn |
S. Wunsch, H. Ku, I. Delwiche, R. Awadallah |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 21, no. 4 ; Nr. 21, no. 4 (2014-08-21), S.855-868 |
| Datensatznummer |
250120934
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| Publikation (Nr.) |
 copernicus.org/npg-21-855-2014.pdf |
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| Zusammenfassung |
| Internal wave beams generated by oceanic tidal flows propagate upward and
interact with the increasing stratification found at the pycnocline. The
nonlinear generation of harmonic modes by internal wave beams incident on a
pycnocline has recently been demonstrated by laboratory experiments and
numerical simulations. In these previous studies, the harmonic modes were
trapped within the pycnocline because their frequencies exceeded that of the
stratified fluid below. Here, two-dimensional numerical simulations are used
to explore the effect of incidence angle on harmonic generation at a thin
pycnocline. At incidence angles less than 30 degrees (typical of oceanic
beams), the lowest harmonic mode freely radiates in the form of an internal
wave beam rather than being trapped within the pycnocline. The results
indicate that nonlinear refraction is the primary mechanism for harmonic
generation at incidence angles exceeding 30 degrees, but that interaction of
the incident and reflected beams is more important at smaller incidence
angles. The simulations are compared to weakly nonlinear theory based on
refraction at the pycnocline. The results yield good agreement for trapped
harmonics, but weakly nonlinear theory substantially underpredicts the
amplitude of the radiated harmonics. |
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