• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.553-563
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• 2008

If an arbitrary topography is approximated to a number of vertical steps, both variational approximation and eigenfunction expansion method can be used to compute linear wave transformation over the bottom. In this study a scatterer method associated with variational approximation is proposed to calculate reflection and transmission coefficients. Present method may be shown to be more simple and direct than the successive-application-matrix method by O'Hare and Davies. And Several numerical examples are given which are in good agreement with existing results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.327-334
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• 2013

The interaction of oblique incident waves with a surface-mounted horizontal porous plate is investigated using matched eigenfunction expansion method under the assumption of linear potential theory. The new boundary condition on the porous plate suggested by Zhao et al.(2010) when it is situated at the still water surface is used. The imaginary part of the first propagating-mode eigenvalue in the fluid region under a horizontal porous plate, is closely related to the energy dissipation across the porous plate. By changing the porosity, plate width, wave frequencies, and incidence angles, the reflection and transmission coefficients as well as the wave loads on the porous plate are obtained. It is found that the transmission coefficients can be significantly reduced by selecting optimal porous parameter b = 5.0, also increasing the plate width and incidence angle.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2004.08a
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• pp.25-32
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• 2004

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2001.08a
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• pp.42-49
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• 2001

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.3
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• pp.170-175
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• 1991

In order to calculate reflection coefficients of surface waves due to underwater obstacles, the hybrid boundary integral equation method is used. Numerical results based on the linear element are verified to the exact solutions for a flat bottom. Reflection coefficient and transmission coefficients for a step are compared to Young's results and the results by EFEM (Kirby et al., 1987), in which reflection coefficients decrease to zero as the periods of incident waves decrease. Reflection coefficients for a sinusiodal hump located on a constant depth increase due to the interaction between humps.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.217-222
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• 1991

Hydralic model experiments for permeable breakwaters with three different shapes of cap concrete were carried out in a two-dimensional wave channel to investigate the shape effects of cap concrete on transmission rate of the incident waves over the breakwaters. The model test results show that energy damping effects are significant in the following order; cap concrete with dissipation holes and apron, cap concrete with apron only, and cap concrete without dissipation holes and apron. It is concluded that the significant damping effects are due to energy dissipation of the incident wave as they pass through the holes and the apron.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.231-233
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• 2010

최근 어항에도 친환경항만을 건설하기 위한 노력이 국제적으로 확산되고 있으며, 우리나라에서도 어항의 정비 및 재개발부분에서 적극적으로 수질개선을 위한 기술 적용이 본격화 되고 있다. 본 연구는 우리나라 남해의 소규모 어항 및 해수욕장에 슬릿형 해안 구조물이 시공된 실해역의 실측자료와 수치해석을 통해 현장적용성의 분석을 수행하였다. 수치실험으로는 파랑작용 평형방정식을 이용하는 SWAN 모델을 구성하고 수리모형실험에서 분석된 실린더 슬릿형 방파제의 반사와 투과계수를 모텔에 도입하였다. 수치실험은 한국해양연구원의 전해역 심해설계파 추정 보고서 II (2005)중의 심해설계파 제원을 사용하였으며, 대상해역의 1970년~2006년 (37년간) 관측된 연최대 풍속자료를 이용하여 모델에 반영하였다. 설리항에서 S, SSE, SE계열의 파랑의 내습에 대한 분석을 수행하였으며, 그 결과 구조물이 항내에서 정온도가 유지되며 해수순환에도 이점이 있음을 현장관측 자료분석과 수치실험결과를 통하여 확인할 수 있었다.

• Journal of Ocean Engineering and Technology
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• v.18 no.5
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• pp.7-14
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• 2004

The interaction of incident manochromatic waves with an array of N surface-piercing porous dual cylindrical structures is investigated in the frame of three-dimensional linear potential theory. The dual cylindrical structure is camposed of concentric two cylinders. The exterior cylinder is porous and the interior cylinder is impermeable. The fluid domain is divided into N+1 regions i.e. a single exterior region and N interior regions. The diffraction potentials in each region representing the scattering of incident waves by an array of porous cylindrical structures are expressed by the Fourier Bessel series. The unknown coefficients in each region are determined by applying the porous boundary condition and continuity of mass flux at the matching boundary. It is found that an array of porous cylindrical structures reduces both the wave forces and the wave run-up, and shows the excellent performance of wave blocking. The results show that various types of breakwater exchanging seawater are prospective by controlling the porosity and the configuration of cylindrical structures.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.63-69
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• 2011

In this paper, the wave forces on a cylindrical aquaculture fish cage, which consists of the porous mesh with the uniform porosity, are analyzed using matched eigenfunction expansion method. The boundary condition on the porous net is derived based on the Darcy's law, which implies that the velocity of the fluid passing through the net is linearly proportional to the pressure difference between two sides of the net. The wave forces and wave responses are investigated by changing the porous parameter of porous net as well as the submerged position (floating type, bottom-mounted type) of an aquaculture fish cage. It is found that the wave forces on a bottom-mounted type are largely decreased compared with that on a floating type. Also, the porosity of the netting structure plays an important role in reducing the wave forces and the wave elevation in the vicinity of an aquaculture fish cage.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.3
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• pp.141-147
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• 2006

A newly designed floating breakwater made of Polyethylene with considering the introduction of new material for being harmony with environment and stability of the floater is developed for a marine ranching. In this study, the new concept in which incident wave dissipates its energy due to the vortex shedding by passing through the pipes and sheets is selected for wave breaking mechanism. Model experiment in order to te st its capability is performed for the regular and irregular waves in ocean engineering basin. Good capability to break the incident wave within the 6 seconds of period and 1 m of height is shown. Breaking efficiency for long period wave is not so good in regular and irregular wave. The results of this study will contribute to the design and construction of the floating breakwater.