Numerical Simulations of Breaking Waves and Steep Waves Past a Vertical Cylinder at Different Keulegan–Carpenter Numbers

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai
Keyword(s):  
Dynamic Pressure ◽  
Vertical Cylinder ◽  
Breaking Waves ◽  
Numerical Results ◽  
Wave Forces ◽  
Breaking Wave ◽  
Wave Loads ◽  
Time Step ◽  
Two Phase ◽  
Steep Waves

A three-dimensional (3D) numerical two-phase flow model based on solving unsteady Reynolds-averaged Navier–Stokes (URANS) equations has been used to simulate breaking waves and steep waves past a vertical cylinder on a 1:10 slope. The volume of fluid (VOF) method is employed to capture the free surface and the k–ω shear–stress transport (k–ω SST) turbulence model is used to simulate the turbulence effects. Mesh and time-step refinement studies have been conducted. The numerical results of wave forces on the structure are compared with the experimental data (Irschik et al., 2004, “Breaking Wave Loads on a Slender Pile in Shallow Water,” Coastal Engineering, Vol. 4, World Scientific, Singapore, pp. 568–581) to validate the numerical model, and the numerical results are in good agreement with the measured data. The wave forces on the structure at different Keulegan–Carpenter (KC) numbers are discussed in terms of the slamming force. The secondary load cycles are observed after the wave front past the structure. The dynamic pressure and velocity distribution, as well as the characteristics of the vortices around the structure at four important time instants, are studied.

CFD Simulations of Spilling Breaking Waves and Steep Waves Past a Monopile Structure at Different KC Numbers

2018 ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai
Keyword(s):  
Breaking Waves ◽  
Numerical Results ◽  
Navier Stokes ◽  
Wave Forces ◽  
Time Step ◽  
Two Phase ◽  
Secondary Load ◽  
Turbulence Effects ◽  
Sst Turbulence Model ◽  
Steep Waves

A 3D numerical two-phase flow model based on solving Unsteady Reynolds-averaged Navier-Stokes (URANS) equations has been used to simulate spilling breaking waves and steep waves past a monopile structure at a 1:10 slope. The volume of fluid (VOF) method is employed to capture the free surface and the k–ω Shear-Stress Transport (k–ω SST) turbulence model is used to simulate the turbulence effects. Mesh and time-step refinement studies have been conducted. The numerical results of wave forces on the structure are compared with the experimental data from Irschik et al. (2004) to validate the numerical model, and the numerical results are in good agreement with the measured data. The wave forces on the structure at different KC numbers are discussed in terms of the generation of the slamming force. The secondary load cycles are observed after the wave front past the structure. The pressure and velocity distribution, as well as the characteristics of the vortices around the structure at four important instants, are studied.

scholarly journals Numerical Simulation of Breaking Wave Loading on Standing Circular Cylinders with Different Transverse Inclined Angles

2020 ◽  
Vol 10 (4) ◽  
pp. 1347
Author(s):  
Sen Qu ◽  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Shuzheng Sun ◽  
Huilong Ren
Keyword(s):  
Experimental Data ◽  
Vertical Cylinder ◽  
Wave Force ◽  
High Order ◽  
Numerical Results ◽  
Circular Cylinders ◽  
Wave Forces ◽  
Breaking Wave ◽  
Time Step ◽  
Inclined Angle

The purpose of this paper is to numerically simulate the breaking wave past a standing cylinder with different transverse inclined angles. The numerical simulations are carried out by solving the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with the k − ω S S T turbulence model. The air–water interface is captured using the Volume of Fluid (VOF) method. The convergence studies on the grid and time-step are performed by examining the total horizontal breaking wave forces on the vertical cylinder. The present numerical results have been validated with the published experimental data. A good agreement is obtained between the present numerical results and the experimental data in terms of the surface elevation and the horizontal breaking wave force. Moreover, the total horizontal breaking wave force is decomposed into low-order and high-order wave forces through Fast Fourier Transform (FFT). It is observed that the free surface elevations in front of the cylinder and the normalized high-order wave force have a minimum value when the transverse inclined angle of the cylinder is 45°. The secondary load causing the higher-harmonic ringing motion of structures is not observed when the cylinder is placed with the transverse inclined angles of 30° and 45°.

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°.

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.

scholarly journals Efficient Wave Modeling Using Nonhydrostatic Pressure Distribution and Free Surface Tracking on Fixed Grids

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Hans Bihs ◽  
Arun Kamath ◽  
Ankit Aggarwal ◽  
Csaba Pakozdi
Keyword(s):  
Stokes Equations ◽  
Wave Model ◽  
Offshore Structures ◽  
3D Simulation ◽  
Wave Forces ◽  
Wave Loads ◽  
Two Phase ◽  
New Approach ◽  
2D Simulation ◽  
Numerical Wave

For the estimation of wave loads on offshore structures, relevant extreme wave events need to be identified. In order to achieve this, long-term wave simulations of relatively large scales need to be performed. Computational fluid dynamics (CFD) based numerical wave tanks with an interface capturing two-phase flow approach typically require too large computational resources. In this paper, a three-dimensional (3D) nonhydrostatic wave model is presented, which solves the Navier–Stokes equations and employs an interface tracking method based on the continuity of the horizontal velocities along the vertical water column. With this approach, relatively fewer cells are needed in the vicinity of the air–water interface compared to CFD-based numerical wave tanks. The numerical model solves the governing equations on a rectilinear grid, which allows for the employment of high-order finite differences. The capabilities of the new wave model are presented by comparing the wave propagation in the tank with the CFD approach in a two-dimensional (2D) simulation. Further, a 3D simulation is carried out to determine the wave forces on a vertical cylinder. The calculated wave forces using the new approach are compared to those obtained using the CFD approach and experimental data. It is seen that the new approach provides a similar accuracy to that from the CFD approach while providing a large reduction in the time taken for the simulation. The gain is calculated to be about 4.5 for the 2D simulation and about 7.1 for the 3D simulation.

Wave Load and Structural Analysis for a Jack-Up Platform in Freak Waves

2007 ◽  
Author(s):  
Ould el Moctar ◽  
Thomas E. Schellin ◽  
Milovan Peric
Keyword(s):  
Structural Model ◽  
Stokes Equations ◽  
Nonlinear Effects ◽  
Breaking Waves ◽  
Wave Loads ◽  
Wave Load ◽  
Two Phase ◽  
Freak Waves ◽  
Highly Nonlinear ◽  
Jack Up

The paper analyzed effects of freak waves on a mobile jack-up drilling platform stationed in exposed waters of the North Sea. Under freak wave conditions, highly nonlinear effects, such as wave run-up on platform legs and impact-related wave loads on the hull, had to be considered. Traditional methods based on the Morison formula needed to be critically examined to accurately predict these loads. Our analysis was based on the use of advanced CFD techniques. The code used here solves the Reynolds-averaged Navier-Stokes equations and relies on the interface-capturing technique of the volume-of-fluid type. It computed the two-phase flow of water and air to describe the physics associated with complex free-surface shapes with breaking waves and air trapping, hydrodynamic phenomena that had to be considered to yield reliable predictions. Lastly, the FEM was used to apply the wave-induced loads onto a comprehensive finite element structural model of the platform, yielding deformations and stresses.

Characteristics of the Wave Slamming Forces on Jacket Structures Under Plunging Breaking Waves Based on Experimental Data

2017 ◽  
Author(s):  
Jithin Jose ◽  
Olga Podrażka ◽  
Ove Tobias Gudmestad ◽  
Witold Cieślikiewicz
Keyword(s):  
Energy Demand ◽  
Clean Energy ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Wave Forces ◽  
Breaking Wave ◽  
Jacket Structures ◽  
Wave Slamming ◽  
Wave Properties

Due to increased energy demand and thrive for clean energy, offshore wind energy has become popular these days. A large number of offshore wind turbines supported by fixed type substructures have been installed, among which jacket structures are getting popular in recent times. The forces from breaking waves are a major concern in the design of offshore structures installed in shallow waters. However, there are only limited studies available regarding breaking wave forces on jacket structures and still there exist many uncertainties in this area. During the WaveSlam experiment carried out in 2013, a jacket structure of 1:8 scale was tested on a large number of breaking wave conditions. Wave properties and the forces on the structure were measured during the experiment. The total wave slamming forces are being filtered from the experimental measured force using the Empirical Mode Decomposition method and local slamming forces are obtained by the Frequency Response Function method. Based on these results, the peak slamming force and slamming coefficients on the jacket members are estimated. The wave parameters (wave height and period) and wave front asymmetry are obtained from measured wave properties. The variation of slamming forces and slamming coefficients with respect to these parameters are also investigated.

On the Occurrence of Strong Higher Harmonic Wave Forces and Induced Ringing Loads on Vertical Cylinders

2002 ◽  
Author(s):  
John Grue ◽  
Morten Huseby
Keyword(s):  
Harmonic Wave ◽  
Vertical Cylinder ◽  
Offshore Structures ◽  
Load Cycle ◽  
Wave Forces ◽  
Wave Elevation ◽  
Secondary Load ◽  
Steep Waves ◽  
Acceleration Of Gravity ◽  
Vertical Cylinders

Experimental observations of a secondary load cycle in the force acting on a vertical cylinder exposed to long and steep waves are discussed. A complementary discussion of the occurrence of ringing of models of offshore structures is given. The height of the secondary load cycle is typically up to about 0.1–0.15 times the peak to peak force on the cylinder. The load cycle is observed for a nondimensional wavenumber kR in the range 0.1–0.33 and for a Froude number Fr = ωζm/gD exceeding about 0.4. Pronounced ringing occurs for the same parameter range. (k the wavenumber, R the cylinder radius, ω the wave frequency, ζm the maximal wave elevation, g the acceleration of gravity, D = 2R.)

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.

Shallow Water Breaking Wave Loads on Vertical Cylinders

2013 ◽  
Vol 694-697 ◽  
pp. 659-664
Author(s):  
Li Xu ◽  
Song Gao ◽  
Da Zheng Wang ◽  
N. Barltrop
Keyword(s):  
Water Surface ◽  
Vertical Cylinder ◽  
Breaking Wave ◽  
Total Force ◽  
Outer Diameter ◽  
Wave Loads ◽  
Cylinder Model ◽  
Vertical Cylinders ◽  
Special Case ◽  
Wave Shapes

Many offshore and harbor structures are composed of cylindrical members. In this paper, the special case of shoaling breaking wave loads on a vertical cylinder is investigated in a tank. A segmented cylinder model with outer diameter of 0.204m and total height of 1m was built and tested. Also a 1:20 slope ramp was constructed in the tank to provide the shoaling effect. During the experiments the total force on each segment of the cylinder was measured and the water surface elevations at the cylinder and in deep water were also recorded. Studies on wave shapes and wave loads are presented here.

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