A Numerical Study on the Evolution of Random Seas With the Occurrence of Rogue Waves

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Zhuowei Zhou ◽  
Ningchuan Zhang ◽  
Guoxing Huang
Keyword(s):  
Numerical Study ◽  
Wave Model ◽  
Rogue Waves ◽  
Experimental Investigations ◽  
Random Wave ◽  
Initial State ◽  
Incoming Wave ◽  
Spectral Parameters ◽  
Excess Kurtosis ◽  
Wave Trains

Abstract Numerous numerical and experimental investigations show that rogue waves present much larger probabilities of occurrence than predicted by the linear random wave model, i.e., Gaussian distributed waves. The deviation from normal statistical events excites a continuous concern about rogue wave research. In this study, rogue waves under long-crested and narrow-banded wave trains are checked using the high-order spectral (HOS)-NST model. The JONSWAP wave spectra with random phases are selected as the initial state of the incoming wave trains. Different values of spectral parameters are chosen to reproduce different random sea states with different Benjamin–Feir index (BFI). Numerical results are compared with the classical experimental study and show good agreements. Statistical properties of rogue waves are recounted again within the analysis of exceedance distribution function (EDF) of wave heights and wave crests. Spectral changes are examined, and the monotonic increases with BFI are stressed. However, no bifurcations are observed for BFI near 1. For large BFI, quasi-resonance interactions dominate the wave nonlinearities, and the resulted dynamic excess kurtosis involves initially monotonic enhancement along with space, peaking at around 20–30 wavelengths, but stays at stably high-level values. The quasi-steady-state of dynamic excess kurtosis after full interaction of wave nonlinearities in time and space demonstrates a continuous emergence of rogue waves much more frequent than normality. The changes of excess kurtosis along x are complicated where BFI near 1 and the occurrence of rogue waves might be enhanced even for BFI slightly inferior to 1.

A Numerical Study on the Evolution of Random Seas With the Occurrence of Rogue Waves

2020 ◽  
Author(s):  
Zhuowei Zhou ◽  
Ningchuan Zhang ◽  
Guoxing Huang
Keyword(s):  
Numerical Study ◽  
Experimental Studies ◽  
Wave Model ◽  
Rogue Waves ◽  
Experimental Investigations ◽  
Random Wave ◽  
Initial State ◽  
Incoming Wave ◽  
Energetic State ◽  
Wave Research

Abstract Numerous numerical and experimental investigations show that rogue waves present a much larger probability of occurrence than expected from the linear random wave model, i.e., Gaussian distributed waves. The deviation from normal statistical events excites a continuous concern about rogue-wave research. In this study, rogue waves under random wave seas are addressed within the framework of the horizontal 1-D fully nonlinear Euler equations. The JONSWAP wave spectra with a different set of random phases are selected as the initial state of the recurrences of incoming wave trains. Different values of spectrum parameters (i.e., enhancement factor γ and significant wave height Hs) for JONSWAP spectra are chosen in order to reproduce different random sea states with different BFI values. The results of the numerical method using in this study are compared with classical experimental studies of rogue waves and show good agreements. Nonlinear wave interactions and the evolution of simulated waves are investigated in order to study the emergence of rogue waves. Statistics analysis is applied to the simulating results to find the deviations with normal distributions. Numerical results reveal that the initial unstable waves need some space to evolve, i.e., around 20 wavelengths, and will keep in an energetic state for the formation of rogue waves.

scholarly journals A NUMERICAL STUDY ON SURFACE WAVE EVOLUTION OVER VISCOELASTIC MUD

2018 ◽  
pp. 64
Author(s):  
Elham Sharifineyestani ◽  
Navid Tahvildari
Keyword(s):  
Surface Wave ◽  
Numerical Study ◽  
Current Model ◽  
Resonance Effect ◽  
Wave Model ◽  
Form Solution ◽  
Random Wave ◽  
Complex Frequency ◽  
Wave Evolution ◽  
Domain Phase

A numerical modeling approach is applied to investigate the combined effect of wave-current-mud on the evolution of nonlinear waves. A frequency-domain phase-resolving wave-current model that solves nonlinear wave-wave interactions is used to solve wave evolution. A comparison between the results of numerical wave model and the laboratory experiments confirms the accuracy of the numerical model. The model is then applied to consider the effect of mud properties on nonlinear surface wave evolution. It is shown that resonance effect in viscoelastic mud creates a complex frequency-dependent dissipation pattern. In fact, due to the resonance effect, higher surface wave frequencies can experience higher damping rates over viscoelastic mud compared to viscous mud in both permanent form solution and random wave scenarios. Thus, neglecting mud elasticity can result in inaccuracies in estimating total wave energy and wave shape.

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.

Reconstruction and Analysis of Freak Waves Generated From Unidirectional Random Waves

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Yuxiang Ma ◽  
Changfu Yuan ◽  
Congfang Ai ◽  
Guohai Dong
Keyword(s):  
Time Series ◽  
Extreme Event ◽  
Wave Model ◽  
Rogue Waves ◽  
Random Wave ◽  
Random Waves ◽  
Long Distance ◽  
Freak Waves ◽  
Freak Wave ◽  
Wave Flume

Abstract The generation of two freak waves in a broadband and a narrowband random series registered in the experiments of Li, J. X., Li, P. F., and Liu, S. X. (2013, “Observations of Freak Waves in Random Wave Field in 2D Experimental Wave Flume,” China Ocean Eng., 27(5), pp. 659–670) is precisely reconstructed using a fully non-hydrostatic water wave model. The simulation results indicate that even when the background spectral bandwidths are different, the evolution processes of the two freak waves are similar. Both freak waves emerge quickly during the transition from normal states to extreme events. The freak waves can persist over a long distance, i.e., approximately 5 peak wavelengths. The reconstructed time series in both the backward and forward locations at which the freak waves were recorded reveal that the largest freak wave crests were not captured in the experiment. The freak waves gradually emerged from an intense wave group. The waves developed quickly during the transition from a normal state to an extreme event. Very deep troughs were also formed in the evolution process. The two freak waves were actually generated via different spectral bandwidth processes, but the generation mechanisms of the rogue waves were similar. By analyzing the time series of the freak wave groups, the formation of the freak waves is found to result from the combined effect of the dispersive focusing, the third-order resonant wave interactions, and the higher harmonics.

scholarly journals A NUMERICAL STUDY OF FREAK WAVE GENERATION IN RANDOM SEAS OVER A SUBMERGED BAR

2018 ◽  
pp. 2
Author(s):  
Yuxiang Ma ◽  
Ruili Fu ◽  
Guohai Dong ◽  
Qiannan Du
Keyword(s):  
Numerical Study ◽  
Wave Model ◽  
Rogue Waves ◽  
Generation Process ◽  
Random Waves ◽  
Freak Waves ◽  
Higher Harmonics ◽  
Severe Accidents ◽  
Random Seas ◽  
Submerged Bar

Freak waves, also called rogue waves and giant waves, are much larger and steeper than the surrounding waves, can cause severe accidents, and can be formed in both coastal and offshore regions. The past researchers on freak waves in coastal regions are mainly focused on the statistical properties, and the generation mechanism of such large waves are not yet discussed intensively. The aim of the present study is to examine the generation process of freak waves in unidirectional propagating random waves over a submerged bar using a fully nonlinear numerical wave model, SWASH. It was found that freak waves are readily formed at the seaward part of the crest of the bar and gradually emerged from an intense wave group. The enhancement of the bound higher harmonics in the shoaling process is the main reason to form such large waves in shallow water. On the crest bar of the bathymetry, the extreme wave gradually vanished, mainly due to the releasing of bound higher-harmonics to free wave components.

A Comparison of Methods for Synthesis of Directional Seas

1989 ◽  
Vol 111 (1) ◽  
pp. 43-48 ◽  
Author(s):  
M. D. Miles ◽  
E. R. Funke
Keyword(s):  
Numerical Simulation ◽  
Finite Number ◽  
Narrow Band ◽  
Numerical Models ◽  
Wave Model ◽  
Random Wave ◽  
Fundamental Wave ◽  
Comparison Of Methods ◽  
Wave Trains ◽  
Spatially Homogeneous

Numerical models for synthesis of directional seas are evaluated. Several authors have recently reported limitations associated with the commonly used double summation model which is neither ergodic nor spatially homogeneous for a finite number of terms. In order to overcome these problems, a modified double summation model is presented which uses unidirectional, narrow-band random wave trains as the fundamental components rather than plane sinusoidal waves. Various alternatives for generating the fundamental wave trains are investigated by numerical simulation and results are also compared to a simpler single summation wave model.

Morphological characterization of bicontinuous structures in polymer blends and microemulsions by the inverse-clipping method in the context of the clipped-random-wave model

2000 ◽  
Vol 61 (6) ◽  
pp. 6773-6780 ◽  
Author(s):  
Hiroshi Jinnai ◽  
Yukihiro Nishikawa ◽  
Sow-Hsin Chen ◽  
Satoshi Koizumi ◽  
Takeji Hashimoto
Keyword(s):  
Polymer Blends ◽  
Wave Model ◽  
Morphological Characterization ◽  
Random Wave

A Numerical Study on the Evolution of Random Seas With the Occurrence of Rogue Waves

2021 ◽  
Author(s):  
Zhuowei Zhou ◽  
Ningchuan Zhang ◽  
Guoxing Huang
Keyword(s):  
Numerical Study ◽  
Rogue Waves ◽  
Random Seas

Numerical Study on Wave Attenuation of Tsunami-Like Wave by Emergent Rigid Vegetation

2021 ◽  
pp. 1-28
Author(s):  
K. Qu ◽  
G. Y. Lan ◽  
S. Kraatz ◽  
W. Y. Sun ◽  
B. Deng ◽  
...  
Keyword(s):  
Solitary Waves ◽  
Wave Energy ◽  
Wave Attenuation ◽  
Tsunami Wave ◽  
Numerical Study ◽  
Wave Model ◽  
Indian Ocean Tsunami ◽  
Vegetation Density ◽  
Rigid Vegetation ◽  
Total Wave

The extreme surges and waves generated in tsunamis can cause devastating damages to coastal infrastructures and threaten the intactness of coastal communities. After the 2004 Indian Ocean tsunami, extensive physical experiments and numerical simulations have been conducted to understand the wave attenuation of tsunami waves due to coastal forests. Nearly all prior works used solitary waves as the tsunami wave model, but the spatial-temporal scales of realistic tsunamis differ drastically from that of solitary waves in both wave period and wavelength. More recent work has questioned the applicability of solitary waves and been looking towards more realistic tsunami wave models. Therefore, aiming to achieve more realistic and accurate results, this study will use a parameterized tsunami-like wave based on wave observations during the 2011 Japan tsunami to study the wave attenuation of a tsunami wave by emergent rigid vegetation. This study uses a high-resolution numerical wave tank based on the non-hydrostatic wave model (NHWAVE). This work examines effects of prominent factors, such as wave height, water depth, vegetation density and width, on the wave attenuation efficiency of emergent rigid vegetation. Results indicate that the vegetation patch can dissipate a considerable amount of the total wave energy of the tsunami-like wave. However, the tsunami-like wave has a higher total wave energy, but also a lower wave energy dissipation rate. Results show that using a solitary instead of a tsunami-like wave profile can overestimate the wave attenuation efficiency of the coastal forest.

scholarly journals Flow Separation Control of Backward-Facing Step Airfoil NACA0015 by Blowing Technique

2019 ◽  
Vol 12 (1) ◽  
pp. 99-119
Author(s):  
Khuder N. Abed
Keyword(s):  
Flow Separation ◽  
Numerical Study ◽  
Leading Edge ◽  
Distribution Coefficients ◽  
Open Circuit ◽  
Experimental Investigations ◽  
Backward Facing Step ◽  
Ansys Fluent ◽  
Flow Separation Control ◽  
Naca 0015

The aim of this paper is to control the flow separation above backward-facing step (BFS) airfoil type NACA 0015 by blowing method. The flow field over airfoil has been studied both experimentally and computationally. The study was divided into two parts: a practical study through which NACA 0015 type with a backward -facing step (located at 44.4% c from leading edge) on the upper surface containing blowing holes parallel to the airfoil chord was used. The tests were done over two-dimensional airfoil in an open circuit suction subsonic wind tunnel with flow velocity 25m/s to obtain the pressure distribution coefficients. A numerical study was done by using ANSYS Fluent software version 16.0 on three models of NACA 0015, the first one has backward-facing step without blowing, the second with single blowing holes and the third have multi blowing holes technique. Both studies (experimental and numerical) were done at low Reynolds number (Re=4.4x105) and all models have chord length 0.27m.The experimental investigations and CFD simulations have been performed on the same geometry dimensions, it has been observed that the flow separation on the airfoil can be delayed by using  velocity blowing (30m/s) on the upper surface. The multi blowing holes with velocity improved the aerodynamics properties.The multi blowing holes and single blowing hole thesame effect onpressure distribution coefficients

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