Distributions of nonlinear wave amplitudes and heights from laboratory generated following and crossing bimodal seas
This paper presents an analysis of the distributions of nonlinear crests, troughs and heights of deep water waves from mixed following sea states generated mechanically in an offshore basin and compares with previous results for mixed crossing seas from the same experiment. The random signals at the...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-05-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | http://www.nat-hazards-earth-syst-sci.net/14/1207/2014/nhess-14-1207-2014.pdf |
| Summary: | This paper presents an
analysis of the distributions of nonlinear crests, troughs and heights of
deep water waves from mixed following sea states generated mechanically in an
offshore basin and compares with previous results for mixed crossing seas
from the same experiment. The random signals at the wavemaker in both types
of mixed seas are characterized by bimodal spectra following the model of
Guedes Soares (1984). In agreement with the Benjamin–Feir mechanism, the
high-frequency spectrum shows a decrease in the peak magnitude and downshift
of the peak with the distance, as well as reduction of the tail. The observed
statistics and probabilistic distributions exhibit, in general, increasing
effects of third-order nonlinearity with the distance from the wavemaker.
However, this effect is less pronounced in the wave systems with two
following wave trains than in the crossing seas, given that they have
identical initial characteristics of the bimodal spectra. The relevance of
third-order effects due to free modes only is demonstrated and assessed by
excluding the vertically asymmetric distortions induced by bound wave effects
of second and third order. The fact that for records characterized by
relatively large coefficient of kurtosis, the empirical distributions for the
non-skewed profiles continue deviating from the linear predictions,
corroborate the relevance of free wave interactions and thus the need of
using higher-order models for the description of wave data. |
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| ISSN: | 1561-8633 1684-9981 |