• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.3
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• pp.240-246
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• 2002

Hydraulic model experiments were conducted fur a series of regular and uni-directional irregular waves propagating over a submerged elliptic shoal. Two different sets of experiments have been studied； one considers regular wave transformation with no breaking, and the other considers uni-directional irregular wave with partial breaking on top of the shoal. The numerical experiments are also performed using a numerical model based on the parabolic approximation equation. The result of the numerical experiments are compared with that of hydraulic experiments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.565-573
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• 2007

The effect of wave and current interactions on irregular wave transformation over a submerged elliptic shoal is investigated based on numerical simulations of the Vincent and Briggs experiment [Vincent, C.L., Briggs, M.J., 1989. Refraction-diffraction of irregular waves over a mound. Journal of Waterway, Port, Coastal and Ocean Engineering, 115(2), pp. 269-284]. The numerical simulations are conducted by a combination of REF/DIF S(a wave model) and SHORECIRC(a current model) and a time dependent phase-resolving wavecurrent model, FUNWAVE. In the simulations, the breaking-induced currents defocus waves behind the shoal and bring on a wave shadow zone that shows relatively low wave height distributions. The computed results of the combined model system agree better with the measurements than the computed results obtained by neglecting wave-current interaction do. In addition, the results of FUNWAVE show a good agreement with the measurements. The agreement indicates that it is necessary to take into account the effect of breaking-induced current on wave refraction when wave-breaking occurs over a submerged shoal.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.216-225
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• 1994

By use of laboratory experiment data set for an elliptic shoal by Berkhoff et al. (1982), both accuracy and Performance tests of numerical results between PCGM (Preconditioned Conjugate Gradient Method) and PA(Parabolic Approximation) are compared. Although both results show good agreement with the experimental data the PA model gives better reproduction of the relatively high amplitudes in the section 4-5 downwave of the shoal, in comparison with the PCGM. The PA model has been proved to be a useful tool for predicting wave transformationsin large shallow water region, but it can be applied only to the case of negligible reflection. On the other hand, there is a need to improve the computational efficiency of the PCGM model which is a finite difference scheme directly derived from the mild slope equation and can handle reflection. By taking the results of th PA model as an input data of the PCGM, the CPU time can be reduced by about 40%.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.557-564
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• 2007

The effect of wave and current interactions on regular wave transformation over a submerged elliptic shoal is investigated based on numerical simulations of the Vincent and Briggs experiment [Vincent, C.L., Briggs, M.J., 1989. Refraction-diffraction of irregular waves over a mound. Journal of Waterway, Port, Coastal and Ocean Engineering, 115(2), pp. 269-284]. The numerical simulations are conducted by constituting two numerical model systems: a combination of SWAN(a wave model) plus SHORECIRC(a current model) and a combination of REF/DIF 1(a wave model) plus SHORECIRC. A time dependent phase-resolving wave-current model, FUNWAVE, is also utilized to simulate the experiment. In the simulations, the breaking-induced currents defocus waves behind the shoal and bring on a wave shadow zone that shows relatively low wave height distributions. The computed results of the two model systems agree better with the measurements than the computed results obtained by neglecting wave-current interaction do. However, it is found that the radiation stresses for standing waves are misevaluated in the wave models. In addition, the results of FUNWAVE show very good agreement with the measurements. The agreement indicates that it is necessary to take into account the effect of breaking-induced current on wave refraction when wave-breaking occurs over a submerged shoal.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1994.07a
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• pp.116-120
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• 1994

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.93-99
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• 1998

Parabolic approximation and sponge layer are applied as open boundary condition for elliptic finite difference wave model. Generalized conjugate gradient method is used as a solution procedure. Using parabolic approximation a large part of spurious reflection is removed at the spherical shoal experiment and sponge layer boundary condition needs more than 2 wave lengths of sponge layer to give similar results. Simulating the propagation of waves on a rectangular harbor, it is identified that iterative scheme can be applied easily for the non-rectangular computational region.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.231-238
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• 1992

Error vector propagation method is applied to the elliptic mild slope equation in order to reduce the computation time. Results from the elliptic, parabolic, and hyperbolic models are compared with experimental data for an elliptic shoal. Also, results of the elliptic and hyperbolic models are compared with experimental data for a detached breakwater. As a result of applying this model. it is concluded that the present model satisfactorily reduces the computation time compared with other numerical models. In the accuracy of solutions, there are some oscillations but the trend compares well with other models.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.619-633
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• 1994

A wave deformation model for general purpose combined refraction, diffraction, and breaking is developed in the shallow water. A parabolic approximation equation considered a higher order diffraction term is derived from the previous mild slope equation. A wave energy dissipation term due to bottom friction and breaking is introduced from the turbulence model. The Crank-Nicoloson implicit scheme is used in the numerical calculation, then the solutions are compared with the various hydraulic experiment data in the circular, the elliptic shoal, and the surf zone. The wave height decay in the surf zone is sensitively affected by the incident wave steepness, and the wave height variation around the elliptic shoal is well explained by the non-linear dispersion relation and the wave energy dissipation term. The model is also applied to a field coastal area and reasonable results are obtained.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.61-66
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• 2006

Two iterative solvers are applied to solve the modified mild slope equation. The elliptic formulation of the governing equation is selected for numerical treatment because it is partly suited for complex wave fields, like those encountered inside harbors. The requirement that the computational model should be capable of dealing with a large problem domain is addressed by implementing and testing two iterative solvers, which are based on the Stabilized Bi-Conjugate Gradient Method (BiCGSTAB) and Generalized Conjugate Gradient Method (GCGM). The characteristics of the solvers are compared, using the results for Berkhoff's shoal test, used widely as a benchmark in coastal modeling. It is shown that the GCGM algorithm has a better convergence rate than BiCGSTAB, and preconditioning of these algorithms gives more than half a reduction of computational cost.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.570-576
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• 2007

수중천퇴가 있는 지형을 통과하며 변형하는 파랑을 실험한 Vincent와 Briggs (1989)의 실험조건을 수치모의하여 파랑과 흐름의 상호작용 효과를 연구하였다. SHORECIRC 흐름모형을 결합한 파랑모형 REF/DIF 1과 SWAN, 그리고 파랑과 흐름을 동시에 수치모의 할 수 있는 FUNWAVE를 이용하여 수중천퇴상을 통과하며 변형하고 또 다시 수중천퇴상에서 발생한 쇄파에 의해 발생된 쇄파류에 의해 변형하는 규칙파를 수치모의하였다. 수중천퇴상에서 쇄파가 발생할 때 잉여파응력의 급격한 변화에 따른 강한 유사제트류가 발생하고, 이 흐름은 수중천퇴후면의 파집중현상을 방해하여 파랑을 천퇴중심축으로부터 바깥쪽으로 굴절시켜, 파고를 상대적으로 감소시키는 역할을 한다. 이러한 역학은 실험결과와 본 연구의 수치모의를 통해 확인할 수 있었고, 이는 파랑쇄파류의 파랑변형에 미치는 역할의 중요성을 확인시켜주는 것이다. 규칙파 모의에 한계가 있는 SWAN과 규칙파 특성상 강하게 나타나는 중복파의 잉여파응력계산에 한계가 있는 REF/DIF 1과 달리 FUNWAVE를 이용한 수치모의는 실험결과와 완벽히 일치하였으며, 수중천퇴 후면에 발생하는 쇄파류와 쇄파류에 의한 쌍 vortex의 발달과정을 잘 보여 주었다.