Comparison of Breaking Wave Kinematics From Numerical Simulations With PIV Measurements

2017 ◽  
Author(s):  
Bülent Düz ◽  
Rene Lindeboom ◽  
Jule Scharnke ◽  
Joop Helder ◽  
Henry Bandringa
Keyword(s):  
Numerical Simulations ◽  
Wave Model ◽  
Breaking Waves ◽  
Research Area ◽  
Breaking Wave ◽  
Strongly Nonlinear ◽  
Wave Kinematics ◽  
Image Velocimetry ◽  
Measurement Results ◽  
Spilling Breakers

Breaking waves have been a popular research area among scientists and engineers since they present a strongly nonlinear and turbulent phenomenon. When these waves encounter an offshore or coastal structure, they exert significant amount of loads and stresses, which may result in a catastrophic consequence. Therefore, it is of utmost importance to study breaking waves and associated phenomena. Inspired by this need, in a recent MARIN experiment kinematics of breaking waves were measured with Particle Image Velocimetry (PIV). Among different types of breaking waves, spilling breakers were selected in this initial campaign. First, a summary of the measurement results will be given. These results will then be used for validation of a Computational Fluid Dynamics (CFD) tool. In numerical simulations two methods were followed in order to reproduce the focused wave: in the first method, the CFD tool was coupled to a nonlinear wave model, and in the second method an iterative scheme was used with the CFD tool. Results from these methods were then compared with the measurements.

scholarly journals NON-BREAKING AND BREAKING WAVE LOADS ON A COOLING WATER OUTFALL

1978 ◽  
Vol 1 (16) ◽  
pp. 148
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Water Level ◽  
Cooling Water ◽  
High Water ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Scale Model ◽  
Breaking Wave ◽  
Wave Loads ◽  
Eastern Canada ◽  
Spilling Breakers

Cooling water from a power generating station in Eastern Canada is pumped to an outfall and distributed into the ocean through discharge ports in the sidewalls of a diffuser cap. The cap is essentially a shell-type structure consisting of a submerged circular cylinder 26.5 ft in diameter and 14 ft high. It is located in 25 ft of water at low water level and 54 ft at high water level. Horizontal forces, vertical forces and overturning moments exerted by waves on a 1:36 scale model of the diffuser cap were measured with and without cooling water discharging from the outfall. Tests were run with regular and irregular waves producing both non-breaking and breaking wave loads on the diffuser cap. The overturning moments measured on the diffuser cap were up to 150 percent greater than those on a solid submerged cylinder sealed to the seabed. Unlike sealed cylinders, all of the wave loads measured on the relatively open structure reached maximum values at approximately the same time. The largest wave loads were measured on the diffuser structure when it was subjected to spilling breakers at low water level. For a given wave height, the spilling breakers caused wave loads up to 100 percent greater than those due to non-breaking waves.

Wave-in-Deck Impact Loads in Relation With Wave Kinematics

2017 ◽  
Author(s):  
Jule Scharnke ◽  
Rene Lindeboom ◽  
Bulent Duz
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Impact Load ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Small Scale ◽  
Impact Loads ◽  
Piv Measurements ◽  
Wave Kinematics ◽  
Image Velocimetry

Breaking waves have been studied for many decades and are still of interest as these waves contribute significantly to the dynamics and loading of offshore structures. In current MARIN research this awareness has led to the setup of an experiment to determine the kinematics of breaking waves using Particle Image Velocimetry (PIV). The purpose of the measurement campaign is to determine the evolution of the kinematics of breaking focussed waves. In addition to the PIV measurements in waves, small scale wave-in-deck impact load measurements on a fixed deck box were carried out in the same wave conditions. To investigate the link between wave kinematics and wave-in-deck impact loads, simplified loading models for estimating horizontal deck impact loads were applied and compared to the measured impact loads. In this paper, the comparison of the model test data to estimated loads is presented.

Breaking Wave Kinematics and Resulting Slamming Pressures on a Vertical Column

2012 ◽  
Author(s):  
Carl Trygve Stansberg ◽  
Kjetil Berget ◽  
Mateusz Graczyk ◽  
Chittiappa Muthanna ◽  
Csaba Pakozdi
Keyword(s):  
Breaking Waves ◽  
Full Scale ◽  
Breaking Wave ◽  
Offshore Platforms ◽  
Scaled Model ◽  
Vertical Column ◽  
Wave Kinematics ◽  
Annual Probability ◽  
Column Wall ◽  
Particle Velocities

A need has been identified to improve the knowledge about extreme slamming loads from breaking waves on vertical columns, such as offshore platforms and wind turbine foundations. Due to strongly nonlinear physical mechanisms and large statistical variability, more and improved experimental data are needed, as well as better qualified design procedures. In this paper, model test data and CFD simulations from a recent study with a fixed vertical column are compared and investigated in more detail. Selected individual extreme slamming events due to energetic breaking waves in 1:40 and 1:125 scaled model tests are presented and considered. Waves correspond approximately to extreme breaking wave occurrences in steep energetic sea states with 10-4 annual probability in the Norwegian sector. Slamming pressures on the column wall are measured in time and space by means of a 7 × 7 pressure sensor array covering 19m2 (full scale). Significant spatial variations are observed. When spatially averaged over the array, the observed highest pressures are typically in the range 1MPa–3MPa (full scale), while smaller measuring areas give higher values. This compares roughly to levels found from recent results in the literature; although exact comparison is difficult due to statistical uncertainty issues. Experiences obtained from parallel CFD and PIV activities are also compared to the experiments, from which free-surface particle velocities up to 25m/s (full scale) are estimated in the worst cases. Finally, a simple empirical formula for a slamming coefficient depending on the actual pressure integration area is suggested based on the results.

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.

Experimental Study of Breaking Wave Impinging and Overtopping a Deck Structure

2016 ◽  
Author(s):  
Yun-Ta Wu ◽  
Kuang-An Chang
Keyword(s):  
High Speed ◽  
Bubbly Flow ◽  
Wave Interaction ◽  
Wave Structure ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Floating Platform ◽  
Wave Flume ◽  
Image Velocimetry ◽  
Physical Insight

This paper presents an experimental work on a breaking wave impinging and overtopping a deck structure. Because the Particle Image Velocimetry (PIV) technique is known of unsuitable of applying in highly aerated flows such as breaking waves, a technology named Bubble Image Velocimetry (BIV) is adopted to quantify the turbulent velocity characteristics in the bubbly region. A high-speed camera is used to capture images during the wave-structure interaction event in the framework of BIV methodology and the images are subsequently processed using cross-correlation for velocity determination. A wave focusing method is employed to generate plunging breaker in a laboratory-scale wave flume, and the model structure is a horizontal, flat and rigid deck that can be considered as a representative of a coastal bridge or an offshore floating platform. The goal is to gain physical insight from the breaking wave interaction with a simplified structure through measuring the kinematics of the bubbly flow.

scholarly journals Electromagnetic Scattering Analysis of the Sea Surface with Single Breaking Waves

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jingjing Wang ◽  
Lixin Guo ◽  
Yiwen Wei ◽  
Shuirong Chai ◽  
Ke Li ◽  
...  
Keyword(s):  
Electromagnetic Scattering ◽  
Grazing Angle ◽  
Wave Model ◽  
Breaking Waves ◽  
Sea Surface ◽  
Breaking Wave ◽  
Frequency Method ◽  
Em Scattering ◽  
Rough Sea Surface ◽  
Rough Sea

A new electromagnetic (EM) scattering model of the sea surface with single breaking waves is proposed based on the high-frequency method in this paper. At first, realistic breaking wave sequences are obtained by solving the fluid equations which are simplified. Then, the rough sea surface is established using the linear filtering method. A new wave model is obtained by combining breaking waves with rough sea surface using a 3D coordinate transformation. Finally, the EM scattering features of the sea surface with breaking waves are studied by using shooting and bouncing rays and the physical theory of diffraction (SBR-PTD). It is found that the structure that is similar to a dihedral corner reflector between the breaking wave and rough sea surface exhibits multiple scattering, which leads to the sea-spike phenomenon that the scattering result of horizontal (HH) polarization is larger than that of vertical (VV) polarization, especially at low-grazing-angle (LGA) incidents with upwind. The sea-spike phenomenon is also closely related to the location of strong scattering.

scholarly journals The Velocity Field Underneath a Breaking Rogue Wave: Laboratory Experiments Versus Numerical Simulations

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 68 ◽  
Author(s):  
Alberto Alberello ◽  
Alessandro Iafrati
Keyword(s):  
Velocity Field ◽  
Numerical Simulations ◽  
Wave Breaking ◽  
Ad Hoc ◽  
Breaking Waves ◽  
Navier Stokes ◽  
Wave Crest ◽  
Driving Mechanisms ◽  
Image Velocimetry ◽  
Particle Image Velocimetry Method

Wave breaking is the most characteristic feature of the ocean surface. Physical investigations (in the field and at laboratory scale) and numerical simulations have studied the driving mechanisms that lead to wave breaking and its effects on hydrodynamic loads on marine structures. Despite computational advances, accurate numerical simulations of the complex breaking process remain challenging. Validation of numerical codes is routinely performed against experimental observations of the surface elevation. However, it is still uncertain whether simulations can accurately reproduce the velocity field under breaking waves due to the lack of ad-hoc measurements. In the present work, the velocity field recorded with a Particle Image Velocimetry method during experiments conducted in a unidirectional wave tank is directly compared to the results of a corresponding numerical simulation performed with a Navier–Stokes (NS) solver. It is found that simulations underpredict the velocity close to the wave crest compared to measurements. Higher resolutions seem necessary in order to capture the most relevant details of the flow.

scholarly journals KINEMATICS OF BREAKING WAVES IN COASTAL REGIONS

1988 ◽  
Vol 1 (21) ◽  
pp. 65
Author(s):  
William J. Easson ◽  
Matthew W.P. Griffiths ◽  
Clive A. Greated
Keyword(s):  
Analytical Solutions ◽  
Breaking Waves ◽  
Coastal Regions ◽  
Wave Flume ◽  
Wave Kinematics ◽  
Spilling Breakers

Waves breaking on various slopes in a wave flume are examined. Plunging and spilling breakers are considered. The parametric results show the consistency of the measurement and the independence of scale. A method is given for predicting the maximum breaking height for a wave of known period in a known depth. The velocity is measured to the crest of the wave and comparisions with numerical and analytical solutions demonstrate the shortcomings of many of the established methods of predicting wave kinematics.

On Modelling Kinematics of Steep Irregular Seaway and Freak Waves

2008 ◽  
Author(s):  
Gu¨nther F. Clauss ◽  
Florian Stempinski ◽  
Robert Stu¨ck
Keyword(s):  
Water Waves ◽  
Wave Train ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Coupling Mechanism ◽  
Fast Method ◽  
Freak Waves ◽  
Irregular Wave ◽  
Wave Kinematics ◽  
Stokes Waves

The realistic modelling of velocity and pressure fields in steep, irregular seaways is still a challenging task, especially when extreme events such as freak waves are under investigation. Conventional wave theories provide fast and reliable results while CFD-codes based on RANSE or potential theory are gaining more acceptance for simulating water waves even though they are still considerably time consuming. This paper presents an approach to approximate irregular wave trains with known surface elevations by interacting Stokes waves of up to third order. This is a fast method to determine the wave potential of wind generated waves for long lasting wave registrations with arbitrary origin. The technique is applied to a steep breaking wave package as well as to a realization of a wave train in a wave tank (scale 1:120) which contain a measured extreme wave sequence. Here, special attention is paid to the distinction between the kinematics of the wave crests in extremely high waves and their surrounding irregular wave field. The predicted wave kinematics are validated by experiments employing particle velocity measurements (by Laser Doppler Velocimetry) as well as by pressure recordings. Kinematics of breaking waves are not covered by concurrent analytical wave theories. To address this deficiency a coupling mechanism between a conventionally determined velocity field with a RANSE/VoF-method is applied.

scholarly journals Characteristics of Breaking Wave Forces on Piles over a Permeable Seabed

2021 ◽  
Vol 9 (5) ◽  
pp. 520
Author(s):  
Zhenyu Liu ◽  
Zhen Guo ◽  
Yuzhe Dou ◽  
Fanyu Zeng
Keyword(s):  
Wave Breaking ◽  
Stokes Equations ◽  
Slope Angle ◽  
Wave Force ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Secondary Wave ◽  
Wave Forces ◽  
Breaking Wave ◽  
Breaking Wave Forces

Most offshore wind turbines are installed in shallow water and exposed to breaking waves. Previous numerical studies focusing on breaking wave forces generally ignored the seabed permeability. In this paper, a numerical model based on Volume-Averaged Reynolds Averaged Navier–Stokes equations (VARANS) is employed to reveal the process of a solitary wave interacting with a rigid pile over a permeable slope. Through applying the Forchheimer saturated drag equation, effects of seabed permeability on fluid motions are simulated. The reliability of the present model is verified by comparisons between experimentally obtained data and the numerical results. Further, 190 cases are simulated and the effects of different parameters on breaking wave forces on the pile are studied systematically. Results indicate that over a permeable seabed, the maximum breaking wave forces can occur not only when waves break just before the pile, but also when a “secondary wave wall” slams against the pile, after wave breaking. With the initial wave height increasing, breaking wave forces will increase, but the growth can decrease as the slope angle and permeability increase. For inclined piles around the wave breaking point, the maximum breaking wave force usually occurs with an inclination angle of α = −22.5° or 0°.

Sign in / Sign up

Export Citation Format

Share Document