 |
| Titel |
Sporadic wind wave horse-shoe patterns |
| VerfasserIn |
S. Yu. Annenkov, V. I. Shrira |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1023-5809
|
| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 6, no. 1 ; Nr. 6, no. 1, S.27-50 |
| Datensatznummer |
250003274
|
| Publikation (Nr.) |
 copernicus.org/npg-6-27-1999.pdf |
|
|
|
|
|
| Zusammenfassung |
| The work considers three-dimensional crescent-shaped
patterns often seen on water surface in natural basins and observed in wave tank
experiments. The most common of these 'horse-shoe-like' patterns appear to be sporadic,
i.e., emerging and disappearing spontaneously even under steady wind conditions. The paper
suggests a qualitative model of these structures aimed at explaining their sporadic
nature, physical mechanisms of their selection and their specific asymmetric form. First,
the phenomenon of sporadic horse-shoe patterns is studied numerically using the novel
algorithm of water waves simulation recently developed by the authors (Annenkov and
Shrira, 1999). The simulations show that a steep gravity wave embedded into widespectrum
primordial noise and subjected to small nonconservative effects typically follows the
simple evolution scenario: most of the time the system can be considered as consisting of
a basic wave and a single pair of oblique satellites, although the choice of this pair
tends to be different at different instants. Despite the effective low-dimensionality of
the multimodal system dynamics at relatively sho ' rt time spans, the role of small
satellites is important: in particular, they enlarge the maxima of the developed
satellites. The presence of Benjamin-Feir satellites appears to be of no qualitative
importance at the timescales under consideration. The selection mechanism has been linked
to the quartic resonant interactions among the oblique satellites lying in the domain of
five-wave (McLean's class II) instability of the basic wave: the satellites tend to push
each other out of the resonance zone due to the frequency shifts caused by the quartic
interactions. Since the instability domain is narrow (of order of cube of the basic wave
steepness), eventually in a generic situation only a single pair survives and attains
considerable amplitude. The specific front asymmetry is found to result from the interplay
of quartic and quintet interactions and non-conservative effects: the growing and grown
satellites have a specific value of phase with respect to the basic wave that corresponds
to downwind orientation of the convex sides of wave fronts. As soon as the phase relation
is violated, the satellite's amplitude quickly decreases down to the noise level. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|