Comparison of Numerical Methods for Wave Generation by VOF-Based Numerical Wave Tank

2011 ◽  
Author(s):  
Bingjie Guo ◽  
Sverre Steen
Keyword(s):  
Grid Size ◽  
Navier Stokes ◽  
Numerical Wave Tank ◽  
Mass Source ◽  
Time Step ◽  
Wave Tank ◽  
Inlet Velocity ◽  
Numerical Wave ◽  
2D And 3D ◽  
Selection Of

Based on the Reyonlds Averaged Navier-Stokes (RANS) equation for incompressible, viscous fluid, a VOF-based numerical wave tank which could accurately generate and absorb waves is investigated. Three different wave-making functions, namely ‘Inlet-velocity boundary condition (IBC)’, ‘Momentum source (MOS)’, ‘Mass source (MAS)’ are investigated, and the advantage of each method is analyzed to guide an optimal selection of these functions. Moreover, the effects of viscous model, grid size, time step, and discretization method on the accuracy of the wave simulation are discussed. The interaction between the wave and current is also studied. In order to verify the applicability of these methods, the numerical results in both 2D and 3D tanks are compared with analytical solutions.

On the mass source internal wave making method for ALE based numerical wave tank

2020 ◽  
Vol 25 (4) ◽  
pp. 1093-1102
Author(s):  
Xiao-Dong Bai ◽  
Wei Zhang ◽  
Jin-Hai Zheng ◽  
Yong Wang
Keyword(s):  
Internal Wave ◽  
Numerical Wave Tank ◽  
Mass Source ◽  
Wave Tank ◽  
Numerical Wave

Numerical Wave Tank Including a Fixed Vertical Cylinder Subjected to Waves, Towards the Investigation of Floating Offshore Wind Turbine Hydrodynamics

2020 ◽  
Author(s):  
Constance Clément ◽  
Pauline Bozonnet ◽  
Guillaume Vinay ◽  
Adria Borras Nadal ◽  
Philippe Pagnier ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Wave Generation ◽  
Hydrodynamic Forces ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Numerical Wave Tank ◽  
Time Step ◽  
Cfd Simulations ◽  
Wave Tank ◽  
Numerical Wave

Abstract Specific engineering tools are used to design Floating Offshore Wind Turbines (FOWT). These so-called aero-hydro-servo-elastic solvers simulate the coupled behaviour of the turbine subjected to wind with the floater motion due to waves, including elasticity of the whole structure. The implemented hydrodynamic forces rely on a strong Oil&Gas background and include potential flow theory and empirical laws, such as Morison forces. The undergoing study aims at re-evaluating the validity range of such theories, when applied to FOWT. To do so, CFD simulations will be run to model wave propagation and interaction with a FOWT floater. Hydrodynamic forces will be extracted from the CFD simulations and compared to current hydrodynamic theories. A fixed cylinder in regular second order deep water waves (steepness of 0.9) is simulated and results are validated against experiments [1]. This basic first case implemented with Open-FOAM using waves2Foam library allows to master regular wave generation and interaction with a rather simple structure, running multiple simulations. Convergence (mesh refinement, time step) and parameterization (numerical schemes, turbulence models) studies are carried out to ensure controlled wave generation. An accurate Numerical Wave Tank (NWT) is finally obtained. However, the resolution of air/water interface with Volume Of Fluid (VOF) MULES method seems to be responsible for extreme air velocities on crests resulting in wave damping. This phenomena is solved by decreasing time step. Hydrodynamic forces on the cylinder match experiments with an error below 3%. As the flow is turbulent (Re = 105), a turbulence model is included in the simulation giving results rather close to the ones obtained without turbulence model.

A MODIFIED WAVEMAKER BOUNDARY CONDITION FOR A NUMERICAL WAVE TANK BASED ON THE WCSPH METHOD

2016 ◽  
Vol 78 (8) ◽  
Author(s):  
Amin Mahmoudi ◽  
Habib Hakimzadeh ◽  
Mohammad Javad Ketabdari ◽  
Hassan Abyn
Keyword(s):  
Boundary Condition ◽  
Navier Stokes ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Eddy Simulation ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Numerical Wave ◽  
Wcsph Method

In this paper a space-averaged Navier–Stokes approach was deployed to Modified Wavemaker Boundary condition for a numerical wave tank.  The developed model is based on the smoothed particle hydrodynamic (SPH) method which is a pure Lagrangian approach and can handle large deformations of the free surface with high accuracy. In this study, the large eddy simulation (LES) turbulent model was coupled with the weakly compressible version of the smoothed particle hydrodynamics (WCSPH) method to Modified Wavemaker Boundary condition for a numerical wave tank. An absorbing wavemaker boundary condition was developed to absorb the second reflecting waves from the wavemaker. The capacity of absorbing secondary reflecting waves and incoming waves in absorbing wavemaker was validated through comparisons of the numerical results with general wavemaker.

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.

Wave-Structure Interaction of Focussed Waves With REEF3D

2016 ◽  
Author(s):  
Hans Bihs ◽  
Mayilvahanan Alagan Chella ◽  
Arun Kamath ◽  
Øivind A. Arnsten
Keyword(s):  
Free Surface ◽  
Level Set ◽  
Wave Structure ◽  
High Order ◽  
Navier Stokes ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Structure Interaction ◽  
Numerical Wave ◽  
Wave Structure Interaction

For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events can become critical from design perspective. In a numerical wave tank, extreme waves can be generated through focussed waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a pre-selected location and time. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface shows good agreement with the measurements from experiments. In further computations, the wave impact of the focussed waves on a vertical circular cylinder is investigated. The focussed wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave-structure interaction problems in particular and for free surface flows in general. The open-source CFD code REEF3D solves the three-dimensional Navier-Stokes equations on a staggered Cartesian grid. Solid boundaries are taken into account with the ghost cell immersed boundary method. For the discretization of the convection terms of the momentum equations, the conservative finite difference version of the fifth-order WENO (weighted essentially non-oscillatory) scheme is used. For temporal treatment, the third-order TVD (total variation diminishing) Runge-Kutta scheme is employed. For the pressure, the projection method is used. The free surface flow is solved as two-phase fluid system. For the interface capturing, the level set method is selected. The level set function can be discretized with high-order differencing schemes. This makes it the appropriate solution for wave propagation problems based on Navier-Stokes solvers, which requires high-order numerical methods to avoid artificial wave damping. The numerical model is fully parallelized based on the domain decomposition, using MPI (message passing interface) for internode communication.

Understanding Regular Waves Effect on Ship by Numerical Wave Tank Simulation

2013 ◽  
Vol 477-478 ◽  
pp. 259-264
Author(s):  
Shaotao Fan ◽  
Cheng Bi Zhao ◽  
You Hong Tang
Keyword(s):  
Three Dimensional ◽  
Unsteady Motion ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Continuity Equations ◽  
Numerical Wave ◽  
Volume Method ◽  
Marine Floating Structures

This study establishes three-dimensional numerical wave tank based on the theory of viscous flow to simulate the unsteady motion response of a Wigley advancing in regular heading waves. The governing equations, Reynolds Averaged Navier-Stokes and continuity equations are discretized by finite volume method, a Reynolds-averaged NavierStokes solver is employed to predict the motions of ship, and volume of fluid method is adopted to capture the nonlinear free surface by writing user-defined functions. The outgoing waves are dissipated inside an artificial damping zone located at the rear part (about 1-2 wave lengths) of the wave tank. The numerical simulation results are compared with theoretical and experimental data from Delft University of Technology, and show good agreement with them. This research can be used to further analyze and predict hydrodynamic performance of ship and marine floating structures in waves and help to extend the applications of numerical wave tank.

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.

scholarly journals VERIFICATION OF MULTI DIRECTIONAL WAVE GENERATION BASED ON THREE-DIMENSIONAL NUMERICAL WAVE TANK

2020 ◽  
pp. 53
Author(s):  
Riku Okajima ◽  
Taro Arikawa
Keyword(s):  
Three Dimensional ◽  
Source Model ◽  
Wave Generation ◽  
Irregular Waves ◽  
Navier Stokes ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Irregular Wave ◽  
Directional Wave ◽  
Numerical Wave

Although it is still tricky to stably solve multi-directional irregular waves using a three-dimensional numerical wave tank, several studies have been carried out in recent years with the development of computers (e.g., Wang et al., 2019). In order to calculate stable multidirectional irregular waves, it is necessary to devise the incident boundary conditions. In this study, the wave generation source model (Yamano et al., 2010), which can generate waves in the calculation domain, was applied to verify the stable multi-directional irregular wave generation based on 3D Navier-Stokes simulations. At first, it was verified whether unidirectional irregular waves could be generated or not. Next, multidirectional irregular waves were verified. The calculation time was also summarized.Recorded Presentation from the vICCE (YouTube Link):

scholarly journals Numerical and Experimental Studies on a Three-Dimensional Numerical Wave Tank

IEEE Access ◽  
2018 ◽  
Vol 6 ◽  
pp. 6585-6593 ◽  
Author(s):  
Xiaojie Tian ◽  
Qingyang Wang ◽  
Guijie Liu ◽  
Wei Deng ◽  
Zhiming Gao
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Numerical Wave
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