Benchmarking of a Computational Fluid Dynamics-Based Numerical Wave Tank for Studying Wave Load Effects on Fixed and Floating Offshore Structures

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Ali Nematbakhsh ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Offshore Structures ◽  
Numerical Results ◽  
Wave Loads ◽  
Numerical Wave Tank ◽  
Wave Load ◽  
Wave Tank ◽  
Load Effects ◽  
Numerical Wave

A computational fluid dynamics (CFD) based numerical wave tank (NWT) is developed and verified to study wave load effects on fixed and free floating offshore structures. The model is based on solving Navier–Stokes equations on a structured grid, level set method for tracking the free surface, and an immersed boundary method for studying wave–structure interaction. This paper deals with establishing and verifying a CFD-based NWT. Various concerns that arise during this establishment are discussed, namely effects of wave reflection which might affect the structure response, damping of waves in downstream, and three-dimensional (3D) effects of the waves. A method is described and verified to predict the time when incoming waves from wave generator are affected by reflecting waves from the structure which can help in better designing the dimensions of NWT. The model is then used to study sway, heave, and roll responses of a floating barge which is nonuniform in density and limited in sway direction by a spring and damper. Also, it is used to study wave loads on a fixed, large diameter, surface piercing circular cylinder. The numerical results are compared with the experimental and other numerical results, and in general very good agreement is observed in all range of studied wave frequencies. It is shown that for the studied fixed cylinder, the Morison equation leads to promising results for wavelength to diameter ratio larger than 2π (kD < 1), while for shorter wavelengths results in considerable over prediction of wave loads, due to simplification of wave diffraction effects.

Optimum Design of Bridge Cross Section with Low Clearance Considering Wave Load Effects Based on Numerical Wave-Tank

2015 ◽  
Vol 73 ◽  
pp. 232-237
Author(s):  
Xiantang Zhang ◽  
Xiujin Chen ◽  
Jinmei Huang ◽  
Hongmin Zhou ◽  
Qing Wang
Keyword(s):  
Optimum Design ◽  
Cross Section ◽  
Numerical Wave Tank ◽  
Wave Load ◽  
Wave Tank ◽  
Load Effects ◽  
Numerical Wave

Development of 3-D Numerical Wave Tank and Applications on Comb-Type Breakwater

2010 ◽  
Author(s):  
Zhuo Fang ◽  
Liang Cheng ◽  
Ningchuan Zhang
Keyword(s):  
Offshore Structures ◽  
Wave Generation ◽  
Irregular Waves ◽  
Secondary Wave ◽  
Wave Forces ◽  
Numerical Wave Tank ◽  
Wave Reflections ◽  
Wave Tank ◽  
Numerical Wave ◽  
Source Wave

In this study, a 3-D numerical wave tank is developed, based on a commercial computational fluid dynamics (CFD) package (FLUENT) to predict wave forces on coastal and offshore structures. A source wave-generation method is introduced to FLUENT through user-defined functions to generate incident waves. Spongy layers are used on both upstream and downstream sides of the wave tank to reduce the effects of wave reflections and secondary wave reflections. Various wave trains, such as linear monochromatic waves, second order Stokes waves and irregular waves were generated by using different source functions. It is demonstrated through numerical examples that the source wave-generation method can accurately generate not only small amplitude waves but also nonlinear waves. The present numerical wave tank is validated against standing waves in front of a vertical breakwater. Interactions between waves and a comb-type breakwater are simulated using the present model. The numerical results are compared with physical experimental results. It is found that the present numerical wave tank simulated the wave and breakwater interactions well.

scholarly journals Generation of Offshore Environments in the Numerical Wave Tank to Model Metocean Conditions Interaction with Offshore Structure Near the Free Surface

2021 ◽  
Vol 945 (1) ◽  
pp. 012018
Author(s):  
Mushtaq Ahmed ◽  
Zafarullah Nizamani ◽  
Akihiko Nakayama ◽  
Montasir Osman
Keyword(s):  
Free Surface ◽  
Offshore Structures ◽  
Operating Conditions ◽  
Wave Crest ◽  
Extreme Conditions ◽  
Numerical Wave Tank ◽  
Offshore Structure ◽  
Wave Tank ◽  
Numerical Wave ◽  
Operating Wave

Abstract Offshore structures play a vital role in the economy of offshore oil-producing countries, where mostly fixed jacket type structures are used to produce oil and gas installed in shallow water. In an offshore environment where structures are installed, there exist met ocean forces such as wind, waves, and currents. These met ocean conditions when interacting with offshore structures near the free surface, generate loads. The estimation of such loads is very much important for the proper design of these structures. The primary aim of this study is to investigate the interaction of waves with a jacket platform by generating offshore environments in the numerical wave tank (NWT). To achieve this goal, ANSYS Fluent is used for the flow analysis by using continuity and Navier Stokes equation. Results are verified and validated with the analytical work. Wave crests under operating condition generate a force of 1.3 MN which is the lowest in magnitude as compared to wave crest which produces 4.5 MN force under extreme conditions. Unlike operating wave crest, the operating wave trough generates a higher force of 1 MN than extreme conditions which account for 1.5 MN forces. Forces produced by the extreme offshore environment are 30% higher than those generated under operating conditions. It is concluded from the results that a positive force is exerted onto the structure during the water entry phase while a negative force is observed when the water leaves the structure.

scholarly journals A Semi-Infinite Numerical Wave Tank Using Discrete Particle Simulations

2020 ◽  
Vol 8 (3) ◽  
pp. 159 ◽  
Author(s):  
Sangmin Lee ◽  
Jung-Wuk Hong
Keyword(s):  
Wave Height ◽  
Numerical Technique ◽  
Analytical Formula ◽  
Offshore Structures ◽  
Wave Steepness ◽  
Numerical Wave Tank ◽  
Time Step ◽  
Wave Tank ◽  
Wide Range ◽  
Numerical Wave

With an increasing number of offshore structures for marine renewable energy, various experimental and numerical approaches have been performed to investigate the interaction of waves and structures to ensure the safety of the offshore structures. However, it has been very expensive to carry out real-scale large experiments and simulations. In this study, numerical waves with various relative depths and a wide range of wave steepness are precisely simulated by minimizing the wave reflection with a mass-weighted damping zone located at the end of a numerical wave tank (NWT). To achieve computational efficiency, optimal variables including initial spacing of smoothed particles, calculation time step, and damping coefficients are studied, and the numerical results are verified by comparison with both experimental data and analytical formula, in terms of wave height, particle velocities, and wave height-to-stroke ratio. Those results show good agreement for all wave steepness smaller than 0.067. By applying the proposed methodology, it is allowed to use a numerical wave tank of which the length is smaller than that of the wave tank used for experiments. The developed numerical technique can be used for the safety analysis of offshore structures through the simulation of fluid-structure interaction.

scholarly journals Estimation of Wave Loads Acting on Stationary Floating Body Using Viscous Numerical Wave Tank Technique

2013 ◽  
Vol 27 (3) ◽  
pp. 43-52
Author(s):  
Kyung-Mi Kim ◽  
Jae-Kyung Heo ◽  
Se-Min Jeong ◽  
Jong-Chun Park ◽  
Wu-Joan Kim ◽  
...  
Keyword(s):  
Floating Body ◽  
Wave Loads ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Numerical Wave

Qualification Criteria for the Verification of Numerical Waves – Part 1: Potential-Based Numerical Wave Tank (PNWT)

2021 ◽  
Author(s):  
Sébastien Fouques ◽  
Eloïse Croonenborghs ◽  
Arjen Koop ◽  
Ho-Joon Lim ◽  
Jang Kim ◽  
...  
Keyword(s):  
Numerical Models ◽  
Laws Of Nature ◽  
Offshore Structures ◽  
Wave Loads ◽  
Wave Impact ◽  
Wave Tank ◽  
Numerical Studies ◽  
Experimental Facilities ◽  
Numerical Wave

Abstract There is an increasing trend towards using numerical wave simulations for the design of offshore structures, especially for the stochastic prediction of nonlinear wave loads like those related to air-gap and wave impact. Unlike experimental facilities, where the complex nonlinear physics of wave propagation is simply enforced by the laws of nature, numerical wave tanks (NWTs) rely on assumptions and simplifications to solve the propagation equations in a reasonable amount of time. It is therefore important to verify the quality of the waves generated by NWTs in terms of realistic physical properties. As part of the effort to develop reliable numerical wave modeling practices in the framework of the “Reproducible Offshore CFD JIP”, qualification criteria are formulated for the wave solutions generated from either potential-flow based or CFD-based codes. The criteria have been developed based on experiences from physical wave tank tests and theoretical/numerical studies. They are being evaluated using results from several numerical models and available benchmark data. This paper presents the proposed qualification criteria and on-going evaluation efforts by comparing results from different codes.

Numerical Modeling of Breaking Waves Over a Reef With a Level-Set Based Numerical Wave Tank

2013 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Michael Muskulus
Keyword(s):  
Level Set ◽  
Wave Breaking ◽  
Stokes Equations ◽  
Numerical Results ◽  
Navier Stokes ◽  
Breaking Wave ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Navier Stokes Equations ◽  
Numerical Wave

Wave breaking is a highly unsteady, non-linear and extremely turbulent phenomenon. During the wave breaking process, the energy of the wave system is focused close to the crest of the wave and a spatial spread of wave energy occurs. Thus, the description of such a physical phenomenon is highly complex and it requires a deep insight into the breaking wave process. The accurate assessment of breaking wave kinematics is essential for an accurate prediction of hydrodynamic loads on structures. Besides, the understanding of the transformation of waves propagating over an artificial or natural reef is important concerning the coastal processes. The numerical model used in this study is a two-phase model, which solves the flow problem for air and water simultaneously. The Navier-Stokes equations are solved on uniform Cartesian grids in two dimensions. The complex free surface is captured by the level set method. A staggered grid is used for the computation with the velocities defined at the cell edges and the pressure at the cell centres. This avoids unphysical pressure oscillations that can occur due to the coupling of pressure and velocity in the incompressible Navier-Stokes equations. The Ghost Cell Immersed Boundary Method is employed to handle the boundary conditions for complex boundaries. Turbulence modelling is carried out using the k-ω model. Discretization of the convective terms is performed using the 5th order Weighted Essentially Non-Oscillatory (WENO) scheme. In this study, a two-dimensional numerical wave tank is used to simulate waves propagating over steep slopes and wave dissipation. The main objective of the present study is to investigate the wave breaking process over a submerged reef. This is accomplished by examining the wave profile during wave breaking and the breaker indices. Also, the numerical results are compared to data from physical experiments and the numerical results exhibit reasonable agreement with experimental data.

Sign in / Sign up

Export Citation Format

Share Document