• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.181-186
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• 2006

In this paper, generation mechanisms of ocean freak waves are briefly introduced in the context of wave-current interaction phenomena. The present model of the fluid motion is based on the Navier-Stokes equations incorporating velocity-pressure formulation because of need to model the nonlinear wave interaction with spatially non-uniform current field. In order to deal with the free surface motion, an Arbitrary Lagrangian-Eulerian (ALE) description is adopted. As an accurate and efficient numerical tool, the spectral element method is presented with general features and specific treatment for the wave-current interaction problem. As an intermediate stage of development, solution procedure and characteristics aspects of the present modeling and numerical method are addressed in detail, and preliminary numerical results prove its accuracy and convergence.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.179-182
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• 2004

This paper deals with a new mathematical formulation of nonlinear wave profile based on Banach fixed point theorem. As application of the formulation and its solution procedure, some numerical solutions was presented in this paper and nonlinear equation was derived. Also we introduce a new operator for iteration and getting solution. A numerical study was accomplished with Stokes' first-order solution and iteration scheme, and then we can know the nonlinear characteristic of Stokes' high-order solution. That is, using only Stokes' first-oder(linear) velocity potential and an initial guess of wave profile, it is possible to realize the corresponding high-oder Stokian wave profile with tile new numerical scheme which is the method of iteration. We proved the mathematical convergence of tile proposed scheme. The nonlinear strategy of iterations has very fast convergence rate, that is, only about 6-10 iterations arc required to obtain a numerically converged solution.

• Journal of Ocean Engineering and Technology
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• v.21 no.2 s.75
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• pp.12-21
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• 2007

As the economy grows and the population increases, we need to develop our coastal area and make use of it for various purposes. Specifically, investigation of the wave interactions on and around the vertical cylinders is very important in the design of the offshore or coastal structures. The nonlinear potential analysis developed so far, although very useful, has been found to be limited in application, as strong nonlinear waves generated by the interference between multilayered cylinders and wave impact forces by breaking waves can hardly be estimated. In this study, using a 3-Dimensional volume tracking method VOF(Volume of Fluid), based on Namer-Stokes equations, was developed to simulate highly nonlinear effects, such as breaking waves at the interface or complicated interference waves among structures. A numerical method for nonlinear interaction wave and vertical cylinders is newly proposed. The wave forces and wave transformations computed by the newly proposed numerical simulation method were compared to the other researcher's experimental results, and the results agree well. Based on the validation of this study, this numerical method is applied to the two vertical cylinders to discuss their nonlinear wave forces and wave transformations, according to the variations of separate distance of vertical cylinders.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.645-650
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• 2016

In this study, we conducted a numerical simulation using Navier-Stokes Solver (HYMO-WASS-3D) in order to analyze wave attenuation under wave-current interaction found in existing hydraulic experiments. It showed that wave energy and wave height are reduced as the wave propagates in coexisting fields between waves and currents. And the wave attenuation became more serious as the velocity of current and thus turbulence intensity were increased at wave-current coexisting field. As well, the wave attenuation became more serious with lower wave height and shorter period when the wave propagates the same distance under interactions between waves and currents.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.282-291
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• 2017

The main aim of this study is to investigate the effect of berm breakwater on wave run-up. A total of 200 numerical analysis tests have been carried out in this paper to investigate the effect of berm width, wave height, and wave period on the wave run-up, using an integrating technique of Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD). Direct application of Navier Stokes equations within the berm width has been used to provide a more reliable approach for studying the wave run-up over berm breakwaters. A well tested Reynolds-averaged Navier-Stokes (RANS) code with the Volume of Fluid (VOF) scheme was adopted for numerical computations. The computational results were compared with theoretical data to validate the model outputs. Numerical results showed that the simulation method can provide accurate estimations for wave run-up over berm breakwaters. It was found that the wave run-up may be decreased by increasing the berm width up to about 36 percent. Furthermore, the wave run-up may increase by increasing the wave height and wave period up to about 53 and 36 percent, respectively. These results may convince the engineers to use this model for design of berm breakwater in actual scale by calculating the Reynolds numbers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.335-344
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• 2011

A curvilinear non-hydrostatic free surface model is developed to investigate nonlinear wave interactions in a circular channel. The proposed model solves the unsteady Navier-Stokes equations in a three-dimensional domain with a pressure correction method, which is one of fractional step methods. A hybrid staggered-grid layout in the vertical direction is implemented, which renders relatively simple resulting pressure equation as well as free surface closure. Numerical accuracy with respect to wave nonlinearity is tested against the fifth-order Stokes solution in a two-dimensional numerical wave tank. Numerical applications center on the evolution of nonlinear waves including diffraction and reflection affected by the curvature of side wall in a circular channel comparing with linear waves. Except for a highly nonlinear bichrmatic wave, the model's results are in good agreement with superimposed analytical solution that neglects nonlinear effects. Through the numerical simulation of the highly nonlinear bichramatic wave, the model shows its capability to investigate the evolution of nonlinear wave groups in a circular channel.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.4
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• pp.169-179
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• 2017

In this study, we applied the wave generation method by relaxation method to the SWASH model, which is a non - hydrostatic numerical model, for stable and accurate wave generation of linear and nonlinear waves. To validate the relaxation wave generation method, we were simulated various wave, including the linear wave and nonliner wave and compared with analytical solution. As a result, the incident wave was successfully generated and propagated in all cases from Stokes waves to cnoidal wave. Also, we were confirmed that the wave height and the waveform were in good agreement with the analytical solution.

• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.8-15
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• 2012

An experimental study was carried out in order to understand the kinematics of bichromatic waves. Bichromatic waves are generated in a two-dimensional wave tank, and measured by panorama PIV technique, which allows the flow fields to be captured with respect to a spatial coordinate system. We compared wave profiles and velocities of wave particles obtained by experiment with theoretical results using Stokes 1st and 2nd order waves. The velocity distribution at wave crest and trough of the highest and lowest point of a bichromatic wave are investigated in this study.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.3
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• pp.610-625
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• 2015

In this paper the wave run-up around a circular column in regular waves is numerically calculated to investigate the applicability of the Modified Marker-Density (MMD) method to prediction of wave run-up around an offshore platform. The MMD method is one of the methods to define the highly nonlinear free surface. The governing equations are the Navier-Stokes equations and the continuity equation which are computed in Cartesian grid system. To validate incident waves generated by numerical simulation, those are compared with the solutions of the Stokes $5^{th}$ order wave theory. The wave run-up simulations are performed varying the steepness and period of incident waves as referred experimental data. The numerical results are compared to the experimental data and the results show good agreements.

• Geomechanics and Engineering
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• v.5 no.6
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• pp.595-611
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• 2013

This paper presents a three-dimensional (3D) integrated numerical model where the wave-induced pore pressures in a porous seabed around breakwater heads were investigated. Unlike previous research, the Navier-Stokes equation is solved with internal wave generation for the flow model, while Biot's dynamic seabed behaviour is considered in the seabed model. With the present model, a parametric study was conducted to examine the effects of wave and soil characteristics and breakwater configuration on the wave-induced pore pressure around breakwater heads. Based on numerical examples, it was found that the wave-induced pore pressures at breakwater heads are greater than that beneath a breakwater. The wave-induced seabed response around breakwater heads become more important with: (i) a longer wave period; (ii) a seabed with higher permeability and degree of saturation; and (iii) larger angle between the incident waves and breakwater. Furthermore, the relative difference of wave-induced pore pressure between fully-dynamic and quasi-static solutions are larger at breakwater heads than that beneath a breakwater.