Wave groupiness analysis of the process of 2D freak wave generation in random wave trains

2015 ◽  
Vol 104 ◽  
pp. 480-488 ◽  
Author(s):  
Jinxuan Li ◽  
Jiqing Yang ◽  
Shuxue Liu ◽  
Xinran Ji
Keyword(s):  
Wave Generation ◽  
Random Wave ◽  
Freak Wave ◽  
Wave Trains ◽  
Wave Groupiness

scholarly journals Numerical Investigation into Freak Wave Effects on Deepwater Pipeline Installation

2020 ◽  
Vol 8 (2) ◽  
pp. 119
Author(s):  
Pu Xu ◽  
Zhixin Du ◽  
Shunfeng Gong
Keyword(s):  
Structure Design ◽  
Random Wave ◽  
Offshore Structure ◽  
Transient Wave ◽  
Engineering Project ◽  
Freak Waves ◽  
Offshore Pipelines ◽  
Freak Wave ◽  
Wave Effects ◽  
Wave Trains

Freak waves are an extreme marine environment factor in offshore structure design and become a potential risk, particularly for laying oil-gas pipelines in deep waters. The objective of this study was to reveal the freak wave effects on dynamic behaviors of offshore pipelines for deepwater installation. Thus, a dedicated finite element model (FEM) for deepwater pipeline installation by the S-lay method was developed with special consideration of freak waves. The FEM also took pipelay vessel motions, pipe–stinger roller interactions, and the cyclic contacts between the pipeline and seabed soil into account. Real vessel and stinger data from an actual engineering project in the South China Sea were collected to obtain an accurate simulation. Moreover, an effective superposition approach of combined transient wave trains and random wave trains was introduced, and various types of freak wave trains were simulated. Extensive numerical analyses of a 12 inch gas pipeline being installed into a water depth of 1500 m were implemented under various freak wave conditions. The noticeable influences of freak waves on the pipeline and seabed responses were identified, which provides significant awareness of offshore pipelines for deepwater installation design and field operation monitoring.

Numerical Investigation of Deepwater S-Lay Pipeline Under Freak Waves

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Pu Xu ◽  
Shunfeng Gong
Keyword(s):  
Structure Design ◽  
Dynamic Responses ◽  
Random Wave ◽  
Superposition Method ◽  
Random Waves ◽  
Transient Wave ◽  
Freak Waves ◽  
Freak Wave ◽  
Offshore Pipeline ◽  
Wave Trains

Abstract Freak wave is an extreme sea state with unexpected and huge wave height, which becomes a potential risk for lay barge and offshore pipeline during deepwater installation. In order to investigate the dynamic responses of deepwater S-lay pipeline induced by freak waves, this study developed a comprehensive numerical model with the particular consideration of the freak wave effect. An enhanced superposition method of combined transient wave trains and random wave trains was presented, and a series of freak wave trains were generated. The induced pipelay vessel motions were simulated by the use of displacement response amplitude operators (RAOs). The pipe–stinger roller interactions in the overbend and the cyclic contacts between the pipeline and seabed soil in the touchdown zone (TDZ) were fully taken into consideration. The developed S-lay model was subsequently utilized to calculate the dynamic responses of the pipelay vessel and offshore pipeline under random waves and freak waves for a comparison. The results illustrated the remarkable influence of freak waves on the systematic behaviors of deepwater S-laying pipeline, which offer a significant theoretical basis for the pipe structure design and pipelay operation safety.

Non-Gaussian Extreme Waves in the Central North Sea

1997 ◽  
Vol 119 (3) ◽  
pp. 146-150 ◽  
Author(s):  
J. Skourup ◽  
N.-E. O. Hansen ◽  
K. K. Andreasen
Keyword(s):  
Wave Height ◽  
North Sea ◽  
Upper Bound ◽  
Wave Crest ◽  
Extreme Waves ◽  
Freak Waves ◽  
Freak Wave ◽  
Wave Trains ◽  
Central North Sea ◽  
Crest Height

The area of the Central North Sea is notorious for the occurrence of very high waves in certain wave trains. The short-term distribution of these wave trains includes waves which are far steeper than predicted by the Rayleigh distribution. Such waves are often termed “extreme waves” or “freak waves.” An analysis of the extreme statistical properties of these waves has been made. The analysis is based on more than 12 yr of wave records from the Mærsk Olie og Gas AS operated Gorm Field which is located in the Danish sector of the Central North Sea. From the wave recordings more than 400 freak wave candidates were found. The ratio between the extreme crest height and the significant wave height (20-min value) has been found to be about 1.8, and the ratio between extreme crest height and extreme wave height has been found to be 0.69. The latter ratio is clearly outside the range of Gaussian waves, and it is higher than the maximum value for steep nonlinear long-crested waves, thus indicating that freak waves are not of a permanent form, and probably of short-crested nature. The extreme statistical distribution is represented by a Weibull distribution with an upper bound, where the upper bound is the value for a depth-limited breaking wave. Based on the measured data, a procedure for determining the freak wave crest height with a given return period is proposed. A sensitivity analysis of the extreme value of the crest height is also made.

scholarly journals VERIFICATION OF KIMURA's THEORY FOR WAVE GROUP STATISTICS

1984 ◽  
Vol 1 (19) ◽  
pp. 43 ◽  
Author(s):  
J.A. Battjes ◽  
G.Ph. Van Vledder
Keyword(s):  
Wave Motion ◽  
Random Phase ◽  
Wave Generation ◽  
Original Form ◽  
Wave Group ◽  
Sea Waves ◽  
Wave Groups ◽  
Wave Groupiness ◽  
Active Wave ◽  
Sea Wave

North Sea wave records, obtained in conditions of active wave generation, have been analyzed with respect to the distribution of the length of wave groups. The results are compared to a theory by Kimura, in its original form as well as with the addition of a new spectral wave groupiness parameter, based on the theory of Gaussian processes. The results lend support to the validity of Kimura's theory, this in turn implies further evidence that the phenomenon of wave groups in sea waves can by and large be explained, both qualitatively and quantitatively, in terms of the linear, random phase model for the wave motion, even in conditions of active wave generation.

Freak Wave Generation in a Wave Basin With HOSM-WG Method

2015 ◽  
Author(s):  
Hidetaka Houtani ◽  
Takuji Waseda ◽  
Wataru Fujimoto ◽  
Keiji Kiyomatsu ◽  
Katsuji Tanizawa
Keyword(s):  
Control Method ◽  
Irregular Waves ◽  
Frequency Bandwidth ◽  
Freak Waves ◽  
Freak Wave ◽  
Wave Basin ◽  
Wave Trains ◽  
Directional Wave ◽  
Wave Maker ◽  
The Difference

A method to produce freak waves with arbitrary spectrum in a fully directional wave basin is presented here. This is an extension of Waseda, Houtani and Tanizawa at OMAE 2013[1], which used “HOSM-WG” based on the higher-order spectral method (HOSM). We used the following three methods to improve the HOSM-WG in [1]: “separation of free waves from bound waves,” “using Biesel’s transfer function in wavenumber space” and “using Schaffer’s 2nd-order wave maker control method.” Modulational wave trains, freak waves in unidirectional irregular waves and freak waves in short-crested irregular waves were generated in a wave basin. The experimental results using the improved HOSM-WG were compared to the HOSM simulation, and good agreements were found. The effectiveness of the improved HOSM-WG was ascertained. We showed that the difference between HOSM-WG and HOSM simulations became larger as wave steepness, frequency bandwidth of the spectrum or directional spreading became larger.

Nonlinear and Dissipative Characteristics of a Combined Random-Cnoidal Wave Field

2017 ◽  
Author(s):  
James M. Kaihatu ◽  
John T. Goertz ◽  
Samira Ardani ◽  
Alex Sheremet
Keyword(s):  
Wave Spectrum ◽  
Leading Edge ◽  
Dissipation Function ◽  
Indian Ocean Tsunami ◽  
Random Wave ◽  
Cnoidal Wave ◽  
State University ◽  
Large Wave ◽  
Wave Flume ◽  
Wave Trains

Images of the 2004 Indian Ocean tsunami at landfall shows a leading edge marked by short waves (“fission” waves). These waves appear to be cnoidal in shape and of a temporal and spatial scale in line with the longest swell present in the region, and may interact with the longer waves in the background random wave spectrum. As part of a comprehensive series of experiments, the Large Wave Flume at Oregon State University (USA) was used to generate and measure the properties of cnoidal, random, and combined cnoidal-random wave trains. Both the nonlinear energy transfer characteristics (via bispectral analysis) and dissipation characteristics (via a proxy dissipation function) are studied for all generated wave conditions. It is generally determined that the characteristics of the cnoidal wave dominate the combined cnoidal-random wave signals if the energy of the cnoidal wave is at least equal to that of the random wave.

scholarly journals RANDOM BREAKING WAVES HORIZONTAL SEABED

1986 ◽  
Vol 1 (20) ◽  
pp. 68 ◽  
Author(s):  
Hans Peter Riedel ◽  
Anthony Paul Byrne
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Breaking Waves ◽  
Random Wave ◽  
Random Waves ◽  
Flume Experiments ◽  
Depth Ratio ◽  
Wave Trains ◽  
Monochromatic Waves

According to wave theories the depth limited wave height over a horizontal seabed has a wave height to water depth ratio (H/d) of about 0.8. Flume experiments with monochromatic waves over a horizontal seabed have failed to produce H/d ratios greater than 0.55. However designers still tend to use H/d 0.8 for their design waves. Experiments have been carried out using random wave trains in the flume over a horizontal seabed. These experiments have shown that the limiting H/d ratio of 0.55 applies equally well to random waves.

Numerical Simulation of Rogue Waves Based on the Fourth-Order NLS Equation for Laboratory Experimental Investigation

2010 ◽  
Author(s):  
Hanhong Hu ◽  
Ning Ma ◽  
Xuefeng Wang ◽  
Xiechong Gu
Keyword(s):  
Experimental Investigation ◽  
Fourth Order ◽  
Rogue Waves ◽  
Structure Design ◽  
Domain Model ◽  
Random Wave ◽  
Offshore Structure ◽  
Nls Equation ◽  
Transient Wave ◽  
Wave Trains

The main purposes of investigating the generation of the rogue waves in offshore engineering include: 1) prediction of its occurrence to protect the offshore structure from attacking; 2) the experimental investigation of rogue waves/structure interaction for the structure design. The latter one calls high requirement of wave generation and calculation. In this paper, we establish a spatial domain model of fourth order nonlinear Schro¨dinger (NLS) equation for describing deep-water wave trains in moving coordinate system. For the first purpose mentioned above, this paper presents the evolution of random wave trains in real sea state described by the Joint North Sea Wave Project (JONSWAP) power spectrum numerically, which is governed by the NLS equation. The parameters of the spectrum are evaluated to discuss their effect on the occurrence of rogue waves. For the second purpose to generate rogue waves in experimental tank efficiently, the transient wave is focused for its allowance of precise determination of concentration place/time. First we simulate the three-dimensional transient waves in the numerical tank modeling the deepwater basin with double-side multi-segmented wave-maker in Shanghai Jiao Tong University (SJTU) with linear superposing theory. To discuss its nonlinearity for the guidance of experiment, the transient wave is set as the initial condition of the NLS equation and the difference from the linear simulation is presented, which could be given as the suggestion to the preparation of experiment.

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