Wave Loads on a Perforated Circular Caisson and Suction Pipe of a Sea Water Intake Structure

2004 ◽  
Author(s):  
K. Vijayalakshmi ◽  
S. Neelamani ◽  
R. Sundaravadivelu
Keyword(s):  
Sea Water ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Loads ◽  
Regular Waves ◽  
Suction Pipe ◽  
Well Model ◽  
Surface Fluctuations ◽  
Run Up ◽  
Intake Structure

The wave force on a seawater intake well model consisting of a perforated circular caisson (500mm diameter) encircling a vertical suction pipe (50mm dia) is measured experimentally. The effect of porosity of the caisson wall, incident wave height and wave period on the in-line forces on the caisson and suction pipe is investigated. The porosity of the caisson was varied from 4.54% to 19.15%. Waves of wide ranges of heights and periods were used. The wave forces on the outer caisson & inner cylinder, water surface fluctuations in the interior & exterior of the caisson and wave run-up on the outer caisson & inner cylinder are studied. The present paper includes the wave forces on the outer perforated circular caisson and inner circular cylinder due to regular waves only.

Wave Action on Double-Cylinder Structure With Perforated Outer Wall

2003 ◽  
Author(s):  
Yucheng Li ◽  
Lu Sun ◽  
Bin Teng
Keyword(s):  
Numerical Experiments ◽  
Fluid Velocity ◽  
Wave Interaction ◽  
Outer Wall ◽  
Wave Force ◽  
Wave Loads ◽  
Linear Solution ◽  
Perforated Wall ◽  
Physical Experiments ◽  
Run Up

Based on an eigenfunction expansion of velocity potential and a linear model between the pressure difference between two sides of a perforated wall and the fluid velocity inside it, a semi-analytic linear solution has been acquired for wave interaction with a combined cylinder with an solid interior column surrounded by a coaxial exterior column with perforated wall at a section in azimuthal direction. Numerical experiments have been carried out to examine the influences on the wave force and wave run-up on the combined cylinders with perforated wall by the porous coefficient, the size of the perforated section, and the ratio between the radii of the interior and the exterior columns. This paper also presents the comparison between the numerical experiments results and the physical experiments results. It is acceptable of the comparison of these two results. The combined cylinder may reduce both the wave run-up and the wave loads on it through combination of certain parameters.

Experimental Study on the Wave Loads on Monopile and Jacket Type Support of Offshore Wind Turbines

2018 ◽  
Author(s):  
Jing Zhang ◽  
Qin Liu ◽  
Xing Hua Shi ◽  
C. Guedes Soares
Keyword(s):  
Experimental Study ◽  
Wind Turbine ◽  
Nonlinear Wave ◽  
Wave Force ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Forces ◽  
Wave Loads ◽  
Morison Equation ◽  
Offshore Wind Turbines

As the offshore fixed wind turbine developed, more ones will be installed in the sea field with the depth 15–50 meters. Wave force will be one of the main forces that dominate the design of the wind turbine base, which is calculated using the Morison equation traditionally. This method can predict the wave forces for the small cylinders if the drag and inertia coefficients are obtained accurately. This paper will give a series scaled tests of monopile and jacket type base of the offshore wind turbine in tank to study the nonlinear wave loads.

Effect of Seabed Slope on Offshore Pile Lateral Behaviour Under Wave Force

2010 ◽  
Author(s):  
Sathyanarayanan Dhandapani ◽  
Muthukkumaran Kasinathan
Keyword(s):  
Finite Element ◽  
Vertical Direction ◽  
Pile Group ◽  
Element Model ◽  
Wave Force ◽  
Wave Forces ◽  
Extreme Conditions ◽  
Offshore Platforms ◽  
Wave Loads ◽  
Offshore Structure

Fixed offshore platforms supported by pile foundations are required to resist dynamic lateral loading due to wave forces. The response of a jacket offshore tower is affected by the flexibility and nonlinear behavior of the supporting piles. In this study, a typical fixed offshore platform is chosen, and dynamic wave analysis is performed on it. Analysis has been performed for normal environmental conditions and extreme conditions. For the foundation, the deflections and reactions at regular intervals along the vertical direction from the seabed have been found out from the dynamic analysis, and the results have been compared for normal and extreme conditions. The aim of this study is to investigate the effects of the combined lateral and vertical loads on pile group foundation of a fixed offshore structure and the effects of seabed slope on the pile responses. To provide a more accurate and effective design for offshore pile foundation systems under axial structural loads and lateral wave loads, a finite element model which is modelled in FLAC3D is employed herein to determine the soil structure interaction under similar loading conditions. Three dimensional modelling and the analyses are done using FLAC3D — a finite element package.

Study on the Motions and Stress of Immersing Tunnel Element under Wave Actions

2013 ◽  
Vol 328 ◽  
pp. 614-622
Author(s):  
Hong Da Shi ◽  
Shui Yu Li ◽  
Dong Wang
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Diffraction Theory ◽  
Wave Force ◽  
Source Distribution ◽  
Wave Forces ◽  
Linear Wave ◽  
Wave Loads ◽  
Distribution Method ◽  
Motion Responses

The dynamic characteristics of large-scale tunnel element are very important for the process of immersion. In the paper, the motions and stress of the element under wave actions were studied. The linear wave diffraction theory and the three-dimensional source distribution method were applied to calculate the wave loads and motion responses of the tunnel element under different incident wave conditions. In the study, there have no cable on the element. On the basis of the above theories, the stress and the motions of the element were studied. The first order wave forces and the second order wave force were deduced, and the motions equation was made.

Calculation of Wave Forces and Internal Loads on a Semi-Submersible at Shallow Draft Using an iVOF Method

2011 ◽  
Author(s):  
Rogier de Bruijn ◽  
Fons Huijs ◽  
Tim Bunnik ◽  
Rene´ Huijsmans ◽  
Marc Gerritsma
Keyword(s):  
Linear Method ◽  
Diffraction Method ◽  
Diffraction Theory ◽  
Model Testing ◽  
Model Tests ◽  
Wave Forces ◽  
Wave Loads ◽  
Regular Waves ◽  
Non Linear ◽  
Linear Effects

When semi-submersibles are floating at shallow draft, only a relatively thin layer of water may be present above the floaters. Model tests and full scale observations have shown that in such cases, even in low waves, non-linear effects significantly influence the wave pattern around the floaters. These non-linear effects make conventional methods based on linear diffraction theory less reliable for the calculation of wave forces and internal loads on a semi-submersible at shallow draft. This paper describes and analyzes the non-linear hydrodynamics affecting the wave loads and internal loads at shallow draft. The feasibility of both ComFLOW and linear diffraction method for the calculation of these loads are assessed. CFD simulations were performed using ComFLOW, a program based on the incompressible Navier-Stokes equations and the improved Volume Of Fluid (iVOF) method. First, the wave loads acting on a fixed semi-submersible in regular waves were calculated with ComFLOW and compared with linear diffraction theory and model tests. Secondly, internal loads were calculated for a moving semi-submersible in regular waves using both ComFLOW and linear diffraction theory. In the ComFLOW simulations, the motions of the semi-submersible were prescribed instead of solved by the method itself. Calculations and comparisons were performed for deep draft and shallow draft conditions. The wave loads on the semi-submersible for shallow draft conditions derived with ComFLOW were reasonably close to the results from model testing, while the results from the linear diffraction method showed significant deviations from the model tests results. The internal loads calculated with ComFLOW were quite close to the results from the linear method, even for shallow draft conditions. Additional model testing is required for validation of the internal loads.

Computational Fluid Dynamics Simulations of Regular and Irregular Waves Past a Horizontal Semi-Submerged Cylinder

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai ◽  
Sopheak Seng
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Wave Height ◽  
Stokes Equations ◽  
Wave Force ◽  
Numerical Results ◽  
Irregular Waves ◽  
Wave Forces ◽  
Regular Waves ◽  
Peak Period

Two-dimensional (2D) numerical simulations have been performed to investigate both regular and irregular waves past a fixed horizontally semisubmerged circular cylinder. The 2D simulations are carried out by solving Navier–Stokes equations discretized by finite volume method. Volume of fluid (VOF) method is employed to capture the free surface in the numerical wave tank (NWT). Validation studies have been performed by comparing the numerical results of free surface waves past the cylinder with the published experimental and numerical data. The present numerical results are in good agreement with both the experimental and the other numerical results in terms of hydrodynamic forces and free surface elevation. Subsequently, the effects of the wave height and the wavelength on wave–structure interaction are investigated by conducting numerical simulations on the regular and the irregular waves past a semisubmerged cylinder at different wave heights and the wavelengths. The averaged and maximum vertical wave forces on the cylinder increase with the increasing wave height. The numerical results for the irregular waves are compared with those induced by the regular waves in terms of the maximum and averaged vertical wave forces. When the significant wave height and the spectral peak period of the irregular waves are equal to the wave height and the wave period of the regular waves, the maximum vertical wave force induced by the irregular waves is larger than that induced by the regular waves, meanwhile, the average vertical wave forces have the contrary relationship.

Correction factors for nonlinear runup and wave forces on a large cylinder

1994 ◽  
Vol 21 (5) ◽  
pp. 762-769 ◽  
Author(s):  
Michael Isaacson ◽  
Kwok Fai Cheung
Keyword(s):  
Experimental Studies ◽  
Diffraction Theory ◽  
Wave Force ◽  
Offshore Structures ◽  
Wave Forces ◽  
Correction Factors ◽  
Wave Loads ◽  
Wave Runup ◽  
Ocean Engineering ◽  
Simplified Approach

A recently developed numerical method for second-order wave diffraction is summarized and is used to develop a simplified approach to predicting nonlinear runup and maximum wave loads for large coastal and offshore structures subjected to regular waves. The perturbation method on which the method is based is extended to provide correction factors for the runup and maximum loads. These correction factors apply directly to the predictions of linear diffraction theory, and are independent of the wave height. The correction factors for runup, maximum force and maximum overturning moment are provided for a range of geometric parameters relating to the case of a large circular cylinder extending from the seabed to the free surface. Nonlinear runup and load maxima calculated by the correction factors are compared with the results of previous experimental studies; in general, favourable agreement is obtained. An example application of the proposed procedure is provided, the importance of nonlinear effects in the evaluation of runup and wave loads is discussed, and the limitations of the results are indicated. Key words: coastal structures, diffraction, hydrodynamics, ocean engineering, offshore structures, wave runup, wave force, waves.

Numerical investigation of multidirectional random wave interaction with a large cylinder

2016 ◽  
Vol 231 (1) ◽  
pp. 271-283 ◽  
Author(s):  
Xinran Ji ◽  
Shuxue Liu ◽  
Jinxuan Li ◽  
Wei Jia
Keyword(s):  
Large Scale ◽  
Vertical Cylinder ◽  
Wave Interaction ◽  
Wave Force ◽  
Random Wave ◽  
Wave Loads ◽  
Wave Basin ◽  
Wave Directionality ◽  
Large Cylinder ◽  
Run Up

To investigate the multidirectional wave run-up and forces on a large cylinder, a numerical model of multidirectional random wave loads on a large-scale cylinder is established based on the linear theory of wave interaction with a large-scale bottom-mounted vertical cylinder. The incident directional wave is specified using a discrete form of the Mitsuyasu-type spreading function. A wave basin experiment was carried out, and the numerical calculation results were verified by the results of the physical experiment. The results indicate that the wave directionality has significant effects on the distribution of the wave run-up around the cylinder. The transverse wave force occurs due to which the multidirectional waves at the two sides of the cylinder are totally different from each other at any time because of the wave directionality. Specially, for the multidirectional random wave with small directional spreading parameter ( s = 5), the transverse force Fy is about 57% of the normal force Fx and cannot be neglected any more. Results can provide reference for the real engineering design.

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.

Wave Forces Acting on a Moving Cylinder

1988 ◽  
Vol 110 (4) ◽  
pp. 315-319 ◽  
Author(s):  
W. Koterayama ◽  
M. Nakamura
Keyword(s):  
Circular Cylinder ◽  
Phase Difference ◽  
Relative Motion ◽  
Wave Force ◽  
Added Mass ◽  
Wave Forces ◽  
Force Measurements ◽  
Regular Waves ◽  
Moving Cylinder ◽  
Fixed Cylinder

Wave forces acting on a surging circular cylinder in regular waves are measured in a wave tank. Experiments are carried on various combinations of the amplitude of a wave and a surge, and the phase difference between them. The results of experiments are compared with those of calculations. The Morison equation extended to the case of relative motion is employed to calculate the forces on the cylinder. The inertia, added mass and drag coefficients used in the calculations are obtained from wave force measurements on a fixed cylinder and forced-surge tests in still water.

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