Numerical Investigation of Regular Waves Interaction With Two Fixed Cylinders in Tandem Arrangement

2018 ◽  
Author(s):  
Zhenghao Liu ◽  
Decheng Wan ◽  
Changhong Hu
Keyword(s):  
Free Surface ◽  
Surface Deformation ◽  
Wave Interaction ◽  
Wave Structure ◽  
Surface Elevation ◽  
Wave Radiation ◽  
Wave Forces ◽  
Tandem Arrangement ◽  
Interaction Of Waves ◽  
Tandem Cylinders

The interaction of waves with fixed or floating structures involves complex wave radiation, wave diffraction and free surface deformation. In this work, the interaction of waves with a pair of cylinders in tandem arrangement is investigated using a numerical wave tank. The numerical simulation is first validated by comparing numerical results and experimental data for regular wave interaction with a single cylinder. Wave interaction with tandem cylinders is investigated for different center-to-center distances between the cylinders. All the numerical simulations are carried out by the in-house CFD solver naoe-FOAM-SJTU which is developed on the open source platform OpenFOAM. The incompressible unsteady Reynolds averaged Navier-Stokes (URANS) equations are adopted as the governing equations. The volume of fluid (VOF) method is applied to capture the free surface. The surface elevation around the cylinders is probed by a series of wave gauges and analyzed using transfer function. The wave forces of upstream and downstream cylinder are discussed in detail. The wave forces experienced by the tandem cylinders is highly influenced by the distance between the cylinders. The local surface elevation and the scattered wave field around the cylinders are also investigated. The results show that the present CFD solver can be an alternative tool to deal with wave-structure interactions.

Focused Plunging Breaking Waves Impact on Cylinder Group in Deep Water

2021 ◽  
Author(s):  
Ting Cui ◽  
Arun Kamath ◽  
Weizhi Wang ◽  
Lihao Yuan ◽  
Duanfeng Han ◽  
...  
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Breaking Waves ◽  
Surface Elevation ◽  
Relative Distance ◽  
Structural Safety ◽  
Wave Forces ◽  
Free Surface Elevation ◽  
Single Cylinder ◽  
Numerical Wave

Abstract The correct estimation of wave loading on a cylinder in a cylinder group under different impact scenarios is essential to determine the structural safety of coastal and offshore structures. This scenario differs from the interaction of waves with a single cylinder but not a lot of studies focus on cylinder groups under different arrangements. In this study, the interaction between plunging breaking waves and cylinder groups in deep water is investigated using the two-phase flow model in REEF3D, an open-source computational fluid dynamics program. The Reynolds-averaged Navier-Stokes equation with the two equation k–Ω turbulence model is adopted to resolve the numerical wave tank, with free surface calculated using the level set method. In this study, focused waves in deep water were modeled with a fixed wave steepness method. Wave breaking occurs when the steepness of the wave crest front satisfies the breaking criteria. The model is validated by comparing the numerical wave forces and free surface elevation with measurements from experiments. The computational results show fairly good agreement with experimental data for both free surface elevation and wave forces. Four cases are simulated to investigate the interaction of breaking waves with a cylinder group with different relative distance, number of cylinders and arrangement. Results show that breaking wave forces on the upstream cylinder are smaller than on a single cylinder with a relative distance of one cylinder diameter. The wave forces on cylinders in the pile group are effected by the relative distance between cylinders. The staggered arrangement has a significant influence on the wave forces on the first and second cylinder. The interaction inside a cylinder group mostly happens between the neighbouring cylinders. These interactions are also effected by the relative distance and the numbers of the neighbouring cylinders.

Numerical Modelling of Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Square Arrangements

2016 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arnsten
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Wave Interaction ◽  
Wave Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters and an accurate numerical modelling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source (Computational Fluid Dynamics) CFD model REEF3D is used to simulate the breaking wave interaction with the multiple cylinders. The numerical model is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations, the level set method for the free surface and the k–ω model for turbulence. The model uses a 5th-order conservative finite difference WENO scheme for the convective discretization and a 3rd-order Runge-Kutta scheme for time discretization. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is seen between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. The breaking wave forces on each cylinder in the group are computed for the two cases and the results are compared with the breaking wave force on a single isolated cylinder. Further, the study investigates the water surface elevations and the free surface flow features around the cylinders. In general, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. The results of the present study show that the interference effects from the neighbouring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

Numerical Simulations of Regular and Irregular Wave Forces on a Horizontal Semi-Submerged Cylinder

2017 ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai ◽  
Sopheak Seng
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Simulations ◽  
Stokes Equations ◽  
Wave Length ◽  
Wave Structure ◽  
Numerical Results ◽  
Irregular Waves ◽  
Wave Forces ◽  
Submerged Cylinder

Two-dimensional (2D) numerical simulations have been performed using OpenFOAM (an open source CFD software package [1]) and waves2Foam (an OpenFOAM based add-on library for wave generations and absorption [2]) to investigate free surface waves past one fixed horizontally semi-submerged cylinder. The 2-D simulations are carried out by solving Navier-Stokes equations which are discretized based on finite volume method (FVM). Volume of Fluid (VOF) method is employed to capture the free surface in the numerical wave tank. Validation studies have been performed by comparing the numerical results of Stokes first-order wave past a semi-submerged circular cylinder with the published experimental data at different incident wave properties. The numerical results are in good agreement with the experimental data. Subsequently, regular and irregular waves past semi-submerged cylinder at different wave heights and the wave lengths are computed numerically to investigate the effect of the wave height and wave length on wave-structure interaction. The numerical results for irregular waves are compared with those induced by regular waves.

scholarly journals Investigation of Higher-Harmonic Wave Forces and Ringing Using CFD Simulations

2018 ◽  
Author(s):  
Arun Kamath ◽  
Hans Bihs ◽  
Csaba Pakozdi
Keyword(s):  
Structural Response ◽  
Vertical Cylinder ◽  
Wave Interaction ◽  
Wave Structure ◽  
Higher Order ◽  
Wave Forces ◽  
Numerical Wave Tank ◽  
Cfd Model ◽  
Structure Interaction ◽  
Wave Structure Interaction

Typical offshore structures are designed as tension-leg platforms or gravity based structures with cylindrical substructures. The interaction of waves with the vertical cylinders in high sea states can result in a resonant response called ringing. Here, the frequency of the structural response is close to the natural frequency of the structure itself and leads to large amplitude motions. This is a case of extreme wave loading in high sea states. This understanding of higher-order wave forces in extreme sea states is an essential parameter for obtaining a safe, reliable and economical design of an offshore structure. The study of such higher-order effects needs detailed near-field modelling of the wave-structure interaction and the associated flow phenomena. In such cases, a Computational Fluid Dynamics (CFD) model that can accurately represent the free surface and further the wave-structure interaction problem can provide important insights into the wave hydrodynamics and the structural response. In this paper, the open source CFD model REEF3D is used to simulate wave interaction with a vertical cylinder and the wave forces on the cylinder are calculated. The harmonic components of the wave force are analysed. The model employs higher-order discretisation schemes such as a fifth-order WENO scheme for convection discretisation and a third-order Runge-Kutta scheme for time advancement on a staggered Cartesian grid. The level set method is used to obtain the free surface, providing a sharp interface between air and water. The relaxation method is used to generate and absorb the waves at the two ends of the numerical wave tank. This method provides good quality wave generation and also the wave reflected from the cylinder are absorbed at the wave generation zone. In this way, the generated waves are not affected by the wave interaction process in the numerical wave tank. This is very essential in the studies of higher-order wave interaction problems which are very sensitive to the incident wave characteristics. The numerical results are compared to experimental results for higher-order forces on a vertical cylinder to validate the numerical model.

Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Two Square Arrangements

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Wave Interaction ◽  
Wave Force ◽  
Maximum Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters, and an accurate numerical modeling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source computational fluid dynamics (CFD) model REEF3D is used to simulate the breaking wave interaction with multiple cylinders. The numerical model is based on the incompressible Reynolds-averaged Navier–Stokes (RANS) equations, the level set method for the free surface, and the k–ω model for turbulence. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is obtained between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. For both configurations, three different tank widths and four different spacings between the cylinders are investigated. The breaking wave forces on each cylinder in the group are computed for each case for the two configurations, and the results are compared with the breaking wave force on a single isolated cylinder. Furthermore, the study investigates the water surface elevations and the free surface flow features around the cylinders. For the closely spaced cylinders in a relatively narrower tank, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. But for the widely spaced cylinder in a relatively wider tank, the forces are higher and lower for the upstream cylinders and downstream cylinders, respectively, than the maximum force on a single isolated cylinder. The results of the present study show that the interference effects from the neighboring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

scholarly journals Numerical simulation of flood waves and calculation of exerted forces on the cylindrical piers in contraction channels with different cross section profiles

2011 ◽  
Vol 14 (2) ◽  
pp. 366-385 ◽  
Author(s):  
Parviz Ghadimi ◽  
Arsham Reisinezhad
Keyword(s):  
Free Surface ◽  
Cross Section ◽  
Time Discretization ◽  
Surface Elevation ◽  
Wave Forces ◽  
Free Surface Elevation ◽  
Numerical Work ◽  
Linear System Of Equations ◽  
Element Technique ◽  
Narrow Section

A numerical model based on two-dimensional shallow water equations is presented. The depth-averaged velocity components with free-surface elevation have been used as independent variables in the model. The finite element technique is applied to discretize the spatial derivatives. Triangular elements with quadratic and linear interpolating functions are employed for two horizontal velocity components and the free-surface elevation, respectively. The standard Galerkin method is applied for discretization of the governing equations. Time discretization is performed using an implicit scheme. The resulting linear system of equations is solved by the GMRES method. The model is validated using three test cases and the results are compared with an analytical solution, the result of numerical work and experimental data, respectively. Favorable agreement was achieved in all three cases. Subsequently, the developed model is applied to simulate free-surface elevation through a channel contraction. The effects of width of the narrow section as well as the profile of the cross section of the channel on the wave forces exerted on a circular cylinder were studied. This was done in a channel with a quartic narrow section. Plots of time histories of the drag coefficient on the cylinder were produced, demonstrating the effects of the mentioned parameters.

Second Order Wave Diffraction Around a Fixed Ship-Shaped Body in Unidirectional Steep Waves

2006 ◽  
Vol 128 (2) ◽  
pp. 89-99 ◽  
Author(s):  
J. Zang ◽  
R. Gibson ◽  
P. H. Taylor ◽  
R. Eatock Taylor ◽  
C. Swan
Keyword(s):  
Free Surface ◽  
Wave Diffraction ◽  
Scattering Problem ◽  
Wave Interaction ◽  
Wave Structure ◽  
Second Order ◽  
Wave Impact ◽  
Focused Wave ◽  
Run Up ◽  
Steep Waves

The objective of this research, part of the EU FP5 REBASDO Program, is to examine the effects of second order wave diffraction in wave run-up around the bow of a vessel (FPSO) in random seas. In this work, the nonlinear wave scattering problem is solved by employing a quadratic boundary element method. A computer program, DIFFRACT, has been developed and recently extended to deal with unidirectional and directional bichromatic input wave systems, calculating second order wave diffraction loads and free surface elevation under regular waves and focused wave groups. The second order wave interaction with a vessel in a unidirectional focused wave group is presented in this paper. Comparison of numerical results and 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.

Free-surface deformation measurement

1997 ◽  
Author(s):  
H. Stahl ◽  
Kevin Stultz ◽  
H. Stahl ◽  
Kevin Stultz
Keyword(s):  
Free Surface ◽  
Surface Deformation ◽  
Deformation Measurement ◽  
Free Surface Deformation
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