• 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.

• 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.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.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.134-142
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• 1990

A wide-angle approximation in the parabolic equation method is presented to calculate wave transformation in the shallow water. The parabolic approximation to the mild-slope equation is obtain-ed by the use of a splitting matrix, which leads to a generalized equation in form. A numerical model based on a finite difference scheme is presented and computational results are provided to test the model against the laboratory measurements of circular and elliptical shoals. The numerical results are in good agreement with most of experimental data. Therefore it can be concluded that the model shows greater capability to reproduce the characteristics of waves in the refractive focus.

• 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

• 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 Korean Society of Coastal and Ocean Engineers
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• v.8 no.2
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• pp.146-150
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• 1996

The waves are most important dynamical factors for the analyses of structural stability and topographical changes on coastal engineering field. However, wind-generated waves are very irregular in shape and transformed through refraction, diffraction and shoaling when they propagate into shallow water where bottom topography and water depth vary significantly. Recently, Vincent and Briggs (1989) reported hydraulic model experiments for the transformation of monochromatic and directionally-spread irregular waves passing over a submerged elliptical mound. They concluded that for the case of combined refraction-diffraction of waves by a shoal, the propagation characteristics of the irregular and equivalent regular wave conditions can be vastly different. On the irregular wave transformation have been made theoretical and numerical studies for several years. Although theoretical and laboratory studies on wave transformation have progressed considerably, field measurement and comparison of numerical results with related theories are still necessary for the prediction of the phenomena in reality. In this study, field measurement of both incident and transformed waves in Youngil Bay were made using various kinds of equipments, and numerical computations were made on the transformed frequency spectra of large waves propagating over the shoal using Chae and Jeong's (1992) elliptic model. It is shown that this model results agree very well with field data, and thus the applicability of the model is now validated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.2
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• pp.164-173
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• 1994

A numerical model to solve mild slope equation is developed by use of a preconditioned conjugate gradient method (PCGM). In the present paper. accurate boundary conditions and a better preconditioner are employed which are improved from the existing method of Panchang et al. (1991). Computational procedures are focused on weakly nonlinear waves, and emerged problems to make a more accurate model are discussed. The results of model are tested against laboratory results of both circular and elliptic shoals. Model results of wave amplitude show excellent agreement with laboratory data and thes thus model can be used as a powerful tool to calculate wave transformation in shallow waters with complex bathymetry.

• 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%.