Wave Diffraction CFD Nonlinear Time–Spectral Simulations in foam–extend (original) (raw)
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Computational Modeling of a Regular Wave Tank
2009 3rd Southern Conference on Computational Modeling, 2009
This paper presents two different numerical methodologies to generate regular gravity waves in a wave tank. We performed numerical simulations of wave generation through the FLUENT ® package, using the Volume of Fluid (VOF) multiphase model to reproduce the wave propagation in the tank. Thus it was possible to analyze two methods for generating regular waves that could be used in future work, especially in the study of devices of energy conversion from ocean waves into electrical energy.
Journal of Ocean Engineering and Marine Energy, 2015
A time-domain 3D Rankine panel method based on a simplified variant of the mixed Eulerian-Lagrangian scheme under certain approximations is developed for studying steep nonlinear waves interacting with practical ship and offshore configurations at zero speed. Appropriate techniques have been developed that enable the method to produce very long-duration simulation results. Two levels of time-domain computations are performed: (1) a fully linear formulation where all external forces are computed on the mean wetted surface, and (2) an approximate nonlinear computation where the hydrodynamics interaction forces (diffraction and radiation forces) are determined on the mean surface and the forces arising from the incident steep waves and hydrostatic restoring forces are determined based upon the exact wetted surface under the nonlinear incident wave. Numerical computations for three practical marine structures, the barge, the S175 hull, and the semisubmersible are presented. The linear computations for which very longduration simulations are achievable from the present method are validated against results from other available methods. As the method is developed for stationary floating bodies undergoing oscillation about their mean location, it cannot be applied for a fully unrestrained body which can freely drift. In absence of physical restraints, the approximate nonlinear calculation requires imposition of artificial constraints partially or fully restraining the horizontal motions.
A note on the difference in the speed of gravity waves in a physical and numerical wave tank
Wave Motion, 2002
Precise measurements of gravity waves with very small wave slope in a physical wave tank are compared with an explicit linear inviscid wave maker theory. The main purpose is to measure the speed of the physical waves relative to those computed. We find that the wave speed in the physical wave tank is slightly less than in the computations. The small difference in the wave speed leads to a relative phase difference between the real waves and the inviscid computations of about 0.01 ± 0.006 rad per wavelength (0.16 ± 0.1%), which is comparable to an estimated phase delay due to the boundary layer at the tank walls. In this result, the estimated effects of weak non-linearity and surface tension in the experiments are subtracted. This relative phase difference is significantly smaller than what previous investigations in wave tanks of similar size have indicated. This means that physical wave tank simulations can effectively be applied as reference for numerical simulations of steep (non-linear) waves.
Modelling and simulation of surface water waves
Mathematics and Computers in Simulation, 2002
The evolution of waves on the surface of a layer of fluid is governed by non-linear effects from surface deformations and dispersive effects from the interaction with the interior fluid motion. Several simulation tools are described in this paper and compared with real life experiments in large tanks of a hydrodynamic laboratory. For the full surface wave equations a numerical FEM/FD program is described that solves both the interior flow and the surface evolution; apart from being very efficient, the program performs remarkably well. For theoretical analysis, simplified equations are desired. These can be obtained by modelling the interior flow to some degree of accuracy, leading to a single equation for the surface elevation. As representatives of this class, we discuss KdV-type of equations and, for wave packets, the NLS equation. We show that even this last equation describes quite well the large, non-symmetric deformations of the envelope of bi-harmonic waves when formulated as a signalling problem.
Wave Generation in a Numerical Wave Tank
2017
Article History: Received: 10 May. 2016 Accepted: 15 Mar. 2017 Developing numerical tanks to study wave structure interaction drew engineers’ attention in last decade. Numerical wave tanks are absolutely essential for investigating wave-structure interaction. This paper presents two different numerical software capabilities to generate regular gravity waves in a wave tank. The wave generation was performed using the FLUENT package and Flow-3D. Both models are based on Navier-Stokes and VoF equations. The results of the mentioned models were compared with theoretical results. Free surface elevation and horizontal component of wave particle velocity were the two parameters which have been considered for comparison. Results indicate that Flow-3D in some cases is a bit more accurate than Fluent in capturing free surface elevation. In numerical models it is important to dissipate wave energy and prevent wave reflection. In this way four different slopes were evaluated to determine the mi...
A comparative study of two fast nonlinear free‐surface water wave models
2011
This paper presents a comparison in terms of accuracy and efficiency between two fully nonlinear potential flow solvers for the solution of gravity wave propagation. One model is based on the high-order spectral (HOS) method, whereas the second model is the high-order finite difference model OceanWave3D. Although both models solve the nonlinear potential flow problem, they make use of two different approaches. The HOS model uses a modal expansion in the vertical direction to collapse the numerical solution to the two-dimensional horizontal plane. On the other hand, the finite difference model simply directly solves the three-dimensional problem. Both models have been well validated on standard test cases and shown to exhibit attractive convergence properties and an optimal scaling of the computational effort with increasing problem size. These two models are compared for solution of a typical problem: propagation of highly nonlinear periodic waves on a finite constant-depth domain. The HOS model is found to be more efficient than OceanWave3D with a difference dependent on the level of accuracy needed as well as the wave steepness. Also, the higher the order of the finite difference schemes used in OceanWave3D, the closer the results come to the HOS model.
Three-dimensional simulation of the runup of nonlinear surface gravity waves
Computational Mathematics and Mathematical Physics, 2014
This paper considers two-dimensional numerical simulation of the run-up of nonlinear surface gravity waves on the basis of Navier-Stokes equations. The statement of the problem is formulated and its boundary and initial conditions are described. A discrete model is constructed using the method of splitting with respect to physical processes. A discrete finite-element model of this problem is developed taking into account the cell fill factor. The conservativeness of the discrete model was investigated and the approximation error of the finite-difference scheme is found. The results of a two-dimensional numerical simulation of the run-up of nonlinear surface gravity waves on coastal structures of shallow-water offshore areas are presented.
Numerical Study on Hydrodynamics of Ships with Forward Speed Based on Nonlinear Steady Wave
Journal of Marine Science and Engineering, 2020
In this paper, an improved potential flow model is proposed for the hydrodynamic analysis of ships advancing in waves. A desingularized Rankine panel method, which has been improved with the added effect of nonlinear steady wave-making (NSWM) flow in frequency domain, is employed for 3D diffraction and radiation problems. Non-uniform rational B-splines (NURBS) are used to describe the body and free surfaces. The NSWM potential is computed by linear superposition of the first-order and second-order steady wave-making potentials which are determined by solving the corresponding boundary value problems (BVPs). The so-called mj terms in the body boundary condition of the radiation problem are evaluated with nonlinear steady flow. The free surface boundary conditions in the diffraction and radiation problems are also derived by considering nonlinear steady flow. To verify the improved model and the numerical method adopted in the present study, the nonlinear wave-making problem of a subm...