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Showing papers on "Rogue wave published in 2000"


Journal ArticleDOI
TL;DR: In this article, the dynamical behavior of these giant waves is addressed as solutions of the nonlinear Schrodinger equation in both 1+1 and 2+1 dimensions, and analytical results for 1 + 1 dimensions are discussed and numerically demonstrated for certain sets of initial conditions.

349 citations


01 Jan 2000
TL;DR: In this paper, the authors present some few evidences which seem to support the existence of a separate freak wave population, which is referred to as abnormal waves, or the "one from nowhere" phenomenon.
Abstract: The possible existence of freak waves is discussed. Our aim is not to present a final answer to the question raised in the paper rifle, but rather present some few evidences which, although not scientifically documented, seem to support the idea of a separate freak wave population. Extremes to be expected within a second order model for the surface elevation will be presented. Based on this, a possible definition of freak waves is suggested. A number of references discussing observations of giant waves are briefly reviewed and commented upon in view of the selected freak wave criterion. As a follow up to the observaflons of giant waves, the paper is briefly discussing some ongoing research on the possible modeling of such events. INTRODUCTION A number of incidents of reported damages to ships and offshore platforms suggest the existence of unexpectedly large waves. Such waves are often referred to as freak waves, abnormal waves, or the "one from nowhere", indicating that observers over the years have considered these events as something beyond the extreme waves typically experienced by marine structures. Are such waves extremely rare realizations of a typical, slightly non-Gaussian population? or Are they typical realizations from a rare strongly non-Gaussian population? If the first question can be answered by "yes", then these waves are in principle accounted for by the present design practice, providing that this practice properly accounts for the typical but slight deviation from the Gaussian assumption regarding the surface process. If, on the other hand, a thorough assessment concludes that the observed giant waves most likely are realizations from a very non-Gaussian surface process, emphasis has to be given to the physical mechanisms that are governing these events. This will include a search for onset mechanisms which over a limited time and space can bring a slightly non-Gaussian surface field into an extremely non-Gaussian surface field possibly involving giant waves. Our expectations are that they will be clearly pronounced only for a rather limited time and space. The closing part of this basic work will be to correlate the possible onset mechanisms to the environmental characteristics adopted for engineering purposes. The kinematics to be associated with a freak wave are needed in order to estimate the structural loading. For a discussion of this, reference is made to e.g. TCrum and Gudmestad (1990). Since we think the phenomenon of freak waves is a rather rare one, a statistical method in combination with available data is not the right way to go. This of course is under the assumption that the physics governing possible freak waves differ from the physics governing the typical pattern. We think that there is some reason to believe that this is the case. In order to establish a proper statistical model for the freak wave characteristics, the model needs to be anchored in the underlying physics. It is therefore recommended that emphasis is given to solving the hydrodynamic equations in time and space allowing the process to behave non-stationary, i.e. realizing that the freak wave phenomenon is of a transient nature. It is important to stress, however, that the existence of such a separate "freak wave population" is far from proved. Robin and Olagnon(199t) have carried out a thorough analysis of wave data from the Frigg field in the North Sea. About 11000 wave records with nearly 2 million individual waves are analyzed. Their conclusion is that the observed extremes, wave heights as well as crest heights, are well within what should be expected when accounting properly for the inherent randomness of the extremes. PROBABILISTIC DESCRIPTION OF SURFACE WAVES Gaussian Model A linear stochastic model for the ocean surface process being in agreement with the linearized hydrodynamic equations is given by, see e.g. Jha(1997): N Re[k~l Bk exp(iogkt)] (1) El (I) =k__~l Ak COS(COk t + Ok) = Re [ ] indicates the real part of a complex number, and Bk = Ak exp(i0k) are the complex Fourier amplitudes. Furthermore, A t and Ok are Rayleigh distributed and uniformly distributed, respectively. The mean square of Ak is related to the underlying wave spectrum, s_=(m), through:

115 citations


Journal ArticleDOI
TL;DR: In this paper, a method to find the wave trains whose evolution leads to the freak wave formation is proposed based on the solution of the Korteweg-de-Vries equation with an initial condition corresponding to the expected freak wave.

100 citations



Journal ArticleDOI
TL;DR: In this article, the irrotational Green-Naghdi model for nonlinear wave propagation in deep water is developed to simulate the irregular sea surface of a given directional wave spectrum.

36 citations




Patent
24 Oct 2000
TL;DR: In this paper, the authors describe a boat with a small profile and a small part of its total structure to the most dynamically active part of all ocean waves, their surface and crests.
Abstract: In operation for wave avoidance the WAY presents only a small profile and a small part of its total structure to the most dynamically active part of all ocean waves, their surface and crests. This includes all storm and rogue waves. In this mode the bulk of the vessel is distributed through lower more quiescent water and spans differentiated deep wave effect. In this mode the WAY has low above-surface reserve buyoancy-able-to-induce unwanted motion. In wave avoidance mode when not underway, the WAY is stabilised by low reserve buoyancy of its wave piercing causeways (12). Underway the WAY behaves as a hydrodynamic flying body and does not rely on wings or hydrofoils which receive undesirable acceleration forces and motion from deep wave effect. Flight path is controlled by orientation which is controlled by a large separation between center of volume and a moveable center of mass. A WAY has a surface or shallow water mode of operation. The word yacht in the title is to suggest a preferred embodiment of size lying between boat and ship; a size that in conventional vessels is subject to particularly nauseating sea motion. The WAY can be configured for passage making with internal motors and without sails.

16 citations


Book ChapterDOI
01 Jul 2000

10 citations


Marc Prevosto1
01 Jan 2000
TL;DR: In this paper, a survey of the statistics of the elevation and kinematics of waves in real seas have been greatly based for specific site studies on in-situ measurements (North-Sea and Gulf of Mexico-ico oil fields).
Abstract: for Rogue Waves 2000 workshop - Brest, 29-30/11/2000 In-situ measurements. The statistics of the elevation and kinematics of waves in real seas have been greatly based for specific site studies on in-situ measurements (North-Sea and Gulf of Mex- ico oil fields). The incomparable great quality of a measurement is that it includes all the physical phenomena, but unfortunately also those which corrupt the actual observation of waves (mooring behavior and transfer function for buoys, fouling effect for plunged or underwater probes, sea foam or spray effect). To this list will be added the problems of spatial integration, calibration and data transformation and transmission. So it becomes difficult to clean the measurements without degrading the extreme or unexpected events. Moreover the wave instruments furnish point mea- surements and so the instrumentation might be very expensive and long to build accurate statis- tics, making cost and duration time not always compatible with the constraints of the project on the site. Apart for some very rich data base, measurements will be used to analyze typical situa- tions and to (in)validate models. Power spectra versus Wave by wave. More and more information on waves are restricted to information on energy. The hindcast models use better wind fields and assimilate larger amount of data (e.g. satellite). They use better models of generation, interaction and dissipation and profit by the always increasing power of the computers. The satellites, too, furnish spectral information with the SAR (directional spectrum) or the altimeters (Hs). The so-called "Wave forecast" of the Meteorological Offices consists in the forecast of sea states (Hs, main direction or directional spectrum) and the step to forecast the corresponding stochastic information on the wave kinematics, is a giant step if we know that we have to introduce informa- tion on the local currents and winds and to take into account complex phenomena, nonlinearities and breaking. To take such a giant step, the addition of small steps will be necessary, some of them have been already taken that we describe hereafter. Methodologies for Statistics. The methodologies to furnish statistics of waves inside a sea state starting from spectral information are of different kinds. They can be based on Monte Carlo tech- niques and development of simulators (Forristall, Prevosto), or derived from theoretical consider- ations: Transformed Gaussian process method (Rychlik), First Order Reliability Method (FORM) (Tromans).

5 citations



01 Jan 2000
TL;DR: In this paper, a wavelet transform analysis of continuous wave recordings in the Sea of Japan during 1986 1990 was carried out to study the incidents of freak waves, and the results showed that a well-defined freak wave can be readily identified from the wavelet spectrum where strong energy density in the spectrum is instantly surged and seemingly carried over to the high frequency components at the time the freak wave occurs.
Abstract: This paper presents a wavelet transform analysis of continuous wave recordings in the Sea of Japan during 1986 1990. The analysis is carried out to study the incidents of freak waves. The results show that a well-defined freak wave can be readily identified from the wavelet spect rum where strong energy density in the spectrum is instantly surged and seemingly carried over to the high frequency components at the ins tant the freak wave occurs. Thus for a given freak wave, there appears a clear corresponding signature shown in the time-frequency wavelet spectrum. Since freak waves are primarily transient events occurring unexpectedly, wavelet transform analysis on continuous, long duration wave measurements clearly represents the most ideal approach to discern the localized characteristics of freak waves for further exploration. 1 I n t r o d u c t i o n Coasta l and open oceans are known to have occasionally observed waves of unusually large size, generally known as the freak waves, which can be hazardous to mariners . As the occurrence of freak waves has been mostly during unknown and unexpec ted conditions, available measurement and analysis are extremely rare. Because of i ts rareness and lack of measurement , nei ther the cause of the occurrence nor a specific definition of freak waves have been sufficiently