Modeling freak waves from the North Sea

Abstract. We present a statistical analysis of freak waves 1 measured during the 203 h of observation on sea surface elevation at a location in the coastal zone of the Baltic Sea (2.7 m depth) during June-July 2008. The dataset contains 97 freak waves occurring in both calm and stormy weather conditions. All of the freak waves are solitary waves, 63% of them having positive shape, 17.5% negative shape and 19.5% sign-variable shape. It is suggested that the freak waves can be divided into two groups. Those of the first group, which includes 92% of the freak waves, have an amplification factor (ratio of freak wave height to significant wave height) which does not vary from significant wave height and has values largely within the range of 2.0 to 2.4; while for the second group, which contain the most extreme freak waves, amplification factors depend strongly on significant wave height and can reach 3.1. Analysis based on the Generalised Pareto distribution is used to describe the waves of the first group and lends weight to the identification of the two groups. It is suggested that the probable mechanism of the generation of freak waves in the second group is dispersive focussing. The time-frequency spectra of the freak waves are studied and dispersive tracks, which can be interpreted as dispersive focussing, are demonstrated.

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“…14), which can be interpreted as a dispersive focussing. Similar analysis of freak waves in the North Sea is reported in (Slunyaev et al, 2005).…”

Section: Freak Waves Of Group II (Abnormal Freak Waves)supporting

confidence: 60%

Freak waves of different types in the coastal zone of the Baltic Sea

Didenkulova

Anderson

2010

Nat. Hazards Earth Syst. Sci.

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“…Numerical modeling performed with a higher-order nonlinear Schrödinger equation can provide more information, as shown in the comparison with real data from field experiment collected in the WACSIS JIP (WAve Crest Sensor Intercomparison Study) done in the work of Liu et al (2005), as well as in other studies that dealt with full-scale data (Slunyaev et al, 2005(Slunyaev et al, , 2013.…”

Section: H D Zhang Et Al: Modeling Extreme Wave Heights From Labormentioning

confidence: 99%

Modeling extreme wave heights from laboratory experiments with the nonlinear Schrödinger equation

Zhang¹,

Soares²,

Cherneva³

et al. 2014

Nat. Hazards Earth Syst. Sci.

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Abstract. Spatial variation of nonlinear wave groups with different initial envelope shapes is theoretically studied first, confirming that the simplest nonlinear theoretical model is capable of describing the evolution of propagating wave packets in deep water. Moreover, three groups of laboratory experiments run in the wave basin of CEHIPAR (Canal de Experiencias Hidrodinámicas de El Pardo, known also as El Pardo Model Basin) was founded in 1928 by the Spanish Navy. are systematically compared with the numerical simulations of the nonlinear Schrödinger equation. Although a little overestimation is detected, especially in the set of experiments characterized by higher initial wave steepness, the numerical simulation still displays a high degree of agreement with the laboratory experiments. Therefore, the nonlinear Schrödinger equation catches the essential characteristics of the extreme waves and provides an important physical insight into their generation. The modulation instability, resulting from the quasi-resonant four-wave interaction in a unidirectional sea state, can be indicated by the coefficient of kurtosis, which shows an appreciable correlation with the extreme wave height and hence is used in the modified Edgeworth-Rayleigh distribution. Finally, some statistical properties on the maximum wave heights in different sea states have been related with the initial Benjamin-Feir index.

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“…2006Slunyaev, et al, 2005;Grue, 2002) and the Kadomtsev-Petviashvili equation (Porubov, et al, 2005), have been used both to model single large-amplitude waves in an experimental basin and to numerically recreate full-scale ocean wave measurements.…”

Section: Administrative Informationmentioning

confidence: 99%