Breaking Wave on a Slender Cylinder: Comparison of Experimental Data and Numerical Results

2012 ◽  
Author(s):  
Jorge Ramirez ◽  
Peter Frigaard ◽  
Thomas Lykke Andersen ◽  
Erik Damgaard Christensen
Keyword(s):  
Target Location ◽  
Experimental Tests ◽  
Offshore Structures ◽  
Breaking Wave ◽  
Linear Wave ◽  
Wave Loads ◽  
Cfd Models ◽  
Focused Wave ◽  
Harmonic Components ◽  
Run Up

CFD models are promising in predicting non-linear wave loads on fixed and floating offshore structures. The NS3 model is described in this paper and it has been validated by means of model test such as wave run-up on monopiles in regular waves. The goal for the use of the NS3 model is to make a detailed investigation of the effect of 2D waves on the run-up height. The focused wave is designed by choosing the phases of the linear harmonic components such that they are in phase at a certain target location. The aim of this paper is the approach on the ability of NS3 model to reproduce these focused wave groups and compare with the results of the experimental tests carried out at Grossen WellenKanal (GWK).

scholarly journals Modelling of Tsunami Due to Submarine Landslide by Smoothed Particle Hydrodynamics Method

2018 ◽  
Vol 203 ◽  
pp. 01001 ◽  
Author(s):  
Vo Nguyen Phu Huan ◽  
Indra Sati H. Harahap ◽  
Wesam Salah Alaloul
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Experimental Tests ◽  
Offshore Structures ◽  
Submarine Landslide ◽  
Tsunami Waves ◽  
Numerical Predictions ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamics Method ◽  
Run Up

Submarine landslide is the most serious threat on both local and regional scales. By way of addition to destroying directly offshore structures, slope failures may also generate destructive tsunami waves. This study has developed a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method to predict four stages of generation, propagation, run-up, and impact of tsunami phenomenon. The numerical predictions in the research were validated with results in the literature and experimental tests. The results of the physical and numerical results presented in this study effort to develop these rule of thumbs to clearly understand some of the mechanics that may play a role in the assessment of tsunami waves.

Non-Linear Wave Diffraction Around a Moored Ship

2004 ◽  
Author(s):  
J. Zang ◽  
R. Gibson ◽  
P. H. Taylor ◽  
R. Eatock Taylor ◽  
C. Swan
Keyword(s):  
Wave Diffraction ◽  
Scattering Problem ◽  
Wave Interaction ◽  
Wave Structure ◽  
Second Order ◽  
Linear Wave ◽  
Wave Impact ◽  
Non Linear ◽  
Focused Wave ◽  
Run Up

The objective of this research, part of the FP5 REBASDO Programme, is to examine the effects of directional wave spreading on the nonlinear hydrodynamic loads and the wave run-up around the bow of a floating vessel (FPSO) in random seas. In this work, the non-linear wave scattering problem is solved by employing a quadratic boundary element method. An existing scheme (DIFFRACT developed in Oxford) has been extended to deal with uni-directional and directional bi-chromatic input wave systems, calculating second-order wave diffraction under regular waves and focused wave groups. The second order wave interaction with a floating vessel in a unidirectional focused wave group is presented in this paper. Comparison of numerical results and the experimental measurements conducted at Imperial College shows excellent agreement. The second-order free surface components at the bow of the ship are very significant, and cannot be neglected if one requires accurate prediction of the wave-structure interaction; otherwise a major underestimation of the wave impact on the structure could occur.

Propagation of Steep and Breaking Short-Crested Waves: A Comparison of CFD Codes

2018 ◽  
Author(s):  
Øystein Lande ◽  
Thomas Berge Johannessen
Keyword(s):  
Wave Propagation ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Offshore Structures ◽  
Practical Reasons ◽  
Breaking Wave ◽  
Linear Wave ◽  
Wave Groups ◽  
Irregular Wave ◽  
Highly Nonlinear

Using the computational fluid domain for propagation of ocean waves have become an important tool for the calculation of highly nonlinear wave loading on offshore structures such as run-up, wave slamming and non-linear breaking wave kinematics. At present, there are many computational fluid dynamics (CFD) codes available which can be employed to calculate water wave propagation and wave induced loading on structures. For practical reasons, however, the use of these codes is often limited to the propagation of regular uni-directional waves initiated very close to the structure, or to investigating the properties and loading due to measured waves by fitting a numerical wave to a measured wave profile. The present paper focuses on the propagation of steep irregular and short crested wave groups up to the point of breaking. Indeed, this is challenging because of the highly nonlinear behavior of irregular wave groups as steepness increases and they approach the point of breaking. The complexity further increases with the introduction of short-crestedness requiring computation in a large 3-dimentional domain. Two CFD codes are used in this comparison study which are believed to be well conditioned for wave propagation, the commercial code ComFLOW (available through the ComFLOW JIP project) and the open-source code BASILISK. The primary objective of this paper to show the two CFD codes capability of recreating measured irregular wave groups, using the known linear wave components from the model test as input to fluid domain. Wave elevation is measured at several locations in the close vicinity of the focus point. The comparison is carried out for a selection of events with variation in steepness, wave spreading and wave spectrum.

Breaking Wave Impacts on Offshore Wind Turbine Foundations: Focused Wave Groups and CFD

2010 ◽  
Author(s):  
Henrik Bredmose ◽  
Niels G. Jacobsen
Keyword(s):  
Breaking Waves ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Wave Loads ◽  
Simple Method ◽  
Wave Groups ◽  
Line Force ◽  
Focused Wave ◽  
Spilling Breakers

Extreme wave loads from breaking waves on a monopile foundation are computed within a 3D CFD model. The wave impacts are obtained by application of focused wave groups. For a fixed position of the monopile, the focus location of the wave group is varied to produce impacts with front shapes that varies from early stages of breaking to broken waves. The CFD results for in-line force are compared to load estimates obtained from the Morison equation. The peak loads determined with this simple method are smaller than those of the CFD solution. The computational results appear to suggest that for the impacts of spilling breakers the peak force gets smaller the more developed the breaking is. This is in qualitative agreement with a finding from shallow water impacts on vertical walls: the strongest wave loads are associated with breakers that hit the structure with slightly overturning front. Extensions of the study are discussed.

scholarly journals Analytical and Experimental Study of Focused Wave Action on a Partially Immersed Box

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Qinghe Fang ◽  
Anxin Guo
Keyword(s):  
Analytical Model ◽  
Analytical Formula ◽  
Hydrodynamic Pressure ◽  
Wave Force ◽  
Laboratory Method ◽  
Wave Forces ◽  
Linear Wave ◽  
Wave Loads ◽  
Side Plate ◽  
Focused Wave

Focused wave is a practical laboratory method for reproducing extreme waves that cause catastrophic damage to marine and coastal structures. This paper presents a simple and efficient analytical method for predicting the hydrodynamic pressure and wave forces acting on a partially immersed box when subjected to a focused wave group attack. The boundary value issue of the physical problem is first investigated to derive an analytical formula based on potential flow theory and the matching eigenfunction method. Thereafter, the test data from a hydrodynamic experiment is used to verify the accuracy of the proposed analytical model. Using the validated analytical model, a parametric analysis is conducted to gain insight into the effects of the structural configuration and wave properties on the pressure and wave forces. It is observed that the hydrodynamic pressure on the offshore side plate, horizontal wave force, and moment are notably influenced by the structure breadth and draft. A focused wave with a lower peak frequency and higher focused amplitude is found to exert greater wave forces on the partially immersed box. The paper shows the value of linear wave theory for wave loads prediction even for focused waves although with some limitations.

Dynamic Response of a Floating Cylinder Subjected to Coupled Wave and Wind Loading

2012 ◽  
Author(s):  
H. Yu ◽  
N. Srivastava
Keyword(s):  
Dynamic Response ◽  
Wind Wave ◽  
Finite Depth ◽  
Offshore Structures ◽  
Wind Loading ◽  
Linear Wave ◽  
Large Radius ◽  
Wave Loads ◽  
Offshore Structure ◽  
Radiation Theory

The broad objective of the research presented herein is to analyze dynamical interactions in offshore structures under combined wind and wave loads for enhanced power delivery and reliability of hybrid wind-wave generation systems. As an offshore structure representative, a model for an inclined floating cylinder at finite depth is developed employing linear wave theory coupled with wind-induced effects. Although detailed wave models have often been incorporated while studying the dynamics of such cylinders, wind-induced effects have been mostly modeled as an axial drag term that affects the drift of the structure along the wind direction. In this article, the effects of not only wind-induced drag, but also lift and oscillations on the structure (i.e. the floating inclined cylinder) are studied. Further, the effects of vortex shedding are considered. Cross-flow principle is used to calculate the wind loads on the cylinder. Assuming small wave steepness and a large radius of cylinder (in comparison to the wavelength), linear wave diffraction and radiation theory coupled with wind-induced effects is employed to analyze the dynamic response of the inclined floating cylinder. Numerical results on the dynamic response of an inclined floating cylinder subjected to coupled wind-wave loading system are presented and discussed while highlighting the increasing relevance of such modeling strategies for hybrid wind-wave power generation systems and their control.

Investigation on Breaking Focused Wave-Induced Loads on a Monopile With CFD Models

2018 ◽  
Author(s):  
Pietro D. Tomaselli ◽  
Ankit Aggarwal ◽  
Erik Damgaard Christensen ◽  
Hans Bihs
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Circular Cylinder ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Experimental Measurements ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
Focused Wave ◽  
Wave Induced

The design of new offshore structures requires the calculation of the wave-induced loads. In this regard, the Computational Fluid Dynamics (CFD) methodology has shown to be a reliable tool, in the case of breaking waves especially. In this paper, two CFD models are tested in the reproduction of an experimental spilling wave impacting a circular cylinder. The numerical results from the models are shown together with the experimental measurements.

scholarly journals Assessment of Numerical Methods for Plunging Breaking Wave Predictions

2021 ◽  
Vol 9 (3) ◽  
pp. 264
Author(s):  
Shanti Bhushan ◽  
Oumnia El Fajri ◽  
Graham Hubbard ◽  
Bradley Chambers ◽  
Christopher Kees
Keyword(s):  
Solitary Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Wave Crest ◽  
Breaking Wave ◽  
Rans Turbulence Models ◽  
Run Up ◽  
Better Than

This study evaluates the capability of Navier–Stokes solvers in predicting forward and backward plunging breaking, including assessment of the effect of grid resolution, turbulence model, and VoF, CLSVoF interface models on predictions. For this purpose, 2D simulations are performed for four test cases: dam break, solitary wave run up on a slope, flow over a submerged bump, and solitary wave over a submerged rectangular obstacle. Plunging wave breaking involves high wave crest, plunger formation, and splash up, followed by second plunger, and chaotic water motions. Coarser grids reasonably predict the wave breaking features, but finer grids are required for accurate prediction of the splash up events. However, instabilities are triggered at the air–water interface (primarily for the air flow) on very fine grids, which induces surface peel-off or kinks and roll-up of the plunger tips. Reynolds averaged Navier–Stokes (RANS) turbulence models result in high eddy-viscosity in the air–water region which decays the fluid momentum and adversely affects the predictions. Both VoF and CLSVoF methods predict the large-scale plunging breaking characteristics well; however, they vary in the prediction of the finer details. The CLSVoF solver predicts the splash-up event and secondary plunger better than the VoF solver; however, the latter predicts the plunger shape better than the former for the solitary wave run-up on a slope case.

A CFD Study of Focused Extreme Wave Impact on Decks of Offshore Structures

2014 ◽  
Author(s):  
Xin Lu ◽  
Pankaj Kumar ◽  
Anand Bahuguni ◽  
Yanling Wu
Keyword(s):  
Real World ◽  
Offshore Structures ◽  
Air Gap ◽  
Irregular Waves ◽  
Linear Wave ◽  
Extreme Wave ◽  
Wave Impact ◽  
Loading Test ◽  
Wide Range ◽  
Wave Maker

The design of offshore structures for extreme/abnormal waves assumes that there is sufficient air gap such that waves will not hit the platform deck. Due to inaccuracies in the predictions of extreme wave crests in addition to settlement or sea-level increases, the required air gap between the crest of the extreme wave and the deck is often inadequate in existing platforms and therefore wave-in-deck loads need to be considered when assessing the integrity of such platforms. The problem of wave-in-deck loading involves very complex physics and demands intensive study. In the Computational Fluid Mechanics (CFD) approach, two critical issues must be addressed, namely the efficient, realistic numerical wave maker and the accurate free surface capturing methodology. Most reported CFD research on wave-in-deck loads consider regular waves only, for instance the Stokes fifth-order waves. They are, however, recognized by designers as approximate approaches since “real world” sea states consist of random irregular waves. In our work, we report a recently developed focused extreme wave maker based on the NewWave theory. This model can better approximate the “real world” conditions, and is more efficient than conventional random wave makers. It is able to efficiently generate targeted waves at a prescribed time and location. The work is implemented and integrated with OpenFOAM, an open source platform that receives more and more attention in a wide range of industrial applications. We will describe the developed numerical method of predicting highly non-linear wave-in-deck loads in the time domain. The model’s capability is firstly demonstrated against 3D model testing experiments on a fixed block with various deck orientations under random waves. A detailed loading analysis is conducted and compared with available numerical and measurement data. It is then applied to an extreme wave loading test on a selected bridge with multiple under-deck girders. The waves are focused extreme irregular waves derived from NewWave theory and JONSWAP spectra.

Experimental study of breaking wave loads on elevated pile cap with rectangular cross-section

2021 ◽  
Vol 227 ◽  
pp. 108878
Author(s):  
Jie Hong ◽  
Kai Wei ◽  
Zhonghui Shen ◽  
Bo Xu ◽  
Shunquan Qin
Keyword(s):  
Experimental Study ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Breaking Wave ◽  
Wave Loads ◽  
Pile Cap
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