• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.153-162
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• 1997

시간평균된 해안의 지하수위는 내륙쪽에 강우가 없는 경우에도 평균해수면 (Mean Sea Level)보다 1내지 2미터 정도 높은 것으로 관측되었다. 이러한 해안의 지하수위상승현상은 주로 파랑과 조석의 작용에 의해 나타난다. 본 연구에서는 지하수위상승에 미치는 조석 및 파랑의 효과를 현장관측결과를 통해 정량적으로 보여주었으며, 또한 이들 각각의 작용에 기인한 지하수위상승에 대한 해석해 및 최근 이론들을 제시하였다. 특히, 최근 지하수의 수리학적 모델링에 관한 연구에서 파랑의 침투 (wave runup infiltration)효과의 중요성이 강조되었는 바, 본 연구를 통해 종래에 보고된 바 없는 swash zone (shoreline과 runup limit사이)에서의 파랑의 침투속도(분포)를 지하수위관측자료를 이용해 간접적으로 산정함으로써 해안의 지하수위예측모델링을 보다 정확히 수행할 수 있으리라 사료된다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.73-75
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• 2018

항만시설 및 배후지를 파랑으로부터 방호하는 기능을 가지는 외곽시설 중 항내 정온을 유지하여 하역효율을 높이고, 항내 항행 및 정박 중인 선박의 안전을 확보하고, 항내시설을 보전하기 위하여 설치하는 것으로는 방파제가 있으며, 배치형태로는 항의 외곽에 설치되는 경우와 연안으로 이격되어 설치되는 경우가 있다. 연안으로 이격되어 설치되는 이안제는 필연적으로 방파제 양단으로 회절파랑이 발생하게 되며 이안제 좌 우측으로 각각 분기되어 진행하는 파랑은 회절에 의해 방파제 배후 안쪽으로 휘어져 위상간 간섭을 일으키며 중첩되면서 전파된다. 지형적인 여건으로 진행방향이 같아지게 되고 항 입구부로 향한다면 파랑의 에너지 중첩에 의한 영향이 항내로 나타날 수 있다. 본 연구에서는 항 입구부에 이안제가 설치되는 경우, 이안제 길이에 따라 발생하는 좌 우측 회절 파랑의 위상차가 항내 파고에 미치는 영향을 수치실험을 통해 검토하였다. 이로부터 항내에서의 파고는 이안제의 길이에 따른 좌 우측 회절 파랑의 위상차에 의한 중첩의 영향으로 증폭 혹은 상쇄되어 나타남을 확인하였다.

• 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 Korea Water Resources Association
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• v.31 no.3
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• pp.223-234
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• 1998

Recently, the interests of the construction of the permeable submerged breakwaters have been increased to preserve and to improve the coastal environment, and to control the incident waves and littoral transport. It is very important to predict the wave transformation precisely over the permeable submerged breakwaters. This study discusses nonlinear wave transformation and characteristics by using BEM based on the frequency domain method of the 3rd-order Stokes waves. The Dupuit-Forchheimer formula is applied to the analysis of the fluid resistance of rubble stones, and the equation about equivalent linear frictional coefficient is newly modified based on the Lorentz's condition for the equivalent work. The numerical results are compared with the experimental ones for verification. These two results give a close agreement each other. It is confirmed that the present method of the 3rd-order Stokes waves estimates more precisely than that of the 2nd-order Stokes waves.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.153-159
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• 2005

Recently, various novel numerical models based on Navier-Stokes equation rave been developed for calculating wave motions in the sea with coastal or ocean structures. Among those models, Volume Of Fluid (VOF) method might be the most popular one, and it has been used for numerical simulations of wave motions including complicated phenomena of wave breakings. VOF method, however, needs enormous computation time and large computational storage memories in general, thus it is practically difficult to use VOF method for calculations in the case of random waves because long and stable computation ( e.g. for more than 100 significant wave periods) is required to obtain statistically meaningful results. On the other hand of the wave motion is potential motion, Boundary Element Method (BEM), which is a much faster and more accurate method than VOF method, am be effectively used. The aim of this study is to develop a new efficient model applicable to calculations of wave motion and/or wave-structure interactions under random waves. To achieve this, a strictly combined BEM-VOF model has been developed by making the best use of both methods' merits; VOF method is used in a restricted fluid domain around a structure where complicated phenomena of wave breakings may exist, and BEM is used in the other domains far from the disturbance where the wave motion may be assumed to be potential. The verification of the model was performed with numerical results for Stokes'5th order wave propagation and a random wave propagation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.558-565
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• 2017

Accurate prediction of wave-structure interactions is important in the safety and design cost effectiveness of fixed and floating offshore structures exposed to extreme environmental conditions. In this study, regular waves and circular column structure interactions for four circular columns in regular waves are analyzed. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. When the four circular columns are arranged in a square array, the interactions according to the incident slopes of the regular waves are analyzed. The wave run-up in the circular column surface was compared according to the slope of the incident wave. It was confirmed that high amplitude waves are generated between the circular columns due to the interaction between the circular column and the incident wave. It is expected that this analytical result will be used as the basic data of the study on the air gap due to the interaction between the structure and incident wave.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.133-138
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• 2008

To analyze incident waves traveling from the deep ocean is very important in that it is based on resolving problems occurred in coastal areas. In general, numerical models and analytical solutions are used to analyze wave transformation. Although a numerical model can be applied to various bottoms and wave conditions, it may have some cumbersome numerical errors. On the other hand, an analytical solution has an advantage of obtaining the solution quickly and accurately without numerical errors. The analytical solution can, however, be utilized only for specific conditions. In this study, the analytical solution of the mild-slope equation has been developed. It can be applied to various conditions combing a numerical technique and an analytical approach while minimizing the numerical errors. As a result of comparing the obtained solutions in this study with those of the previously developed numerical model, A good agreement was observed.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.77-90
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• 1997

Wave deformation due to Oscillating water column (OWC) plant was studied. To solve this problem, three dimensional numerical method based on Improved Green integral equation was applied. Method condition was considered as well as fixed condition and freely floating condition. From the calculation results, main characteriatic of wave deformation due to OWC plant were discussed. Also, some calculations for the floating barge were performed to confirm the validity of numerical solution of the method.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2000.09a
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• pp.120-125
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• 2000

연안역의 토지이용이 극대화됨에 따라 연안구조물이나 항만구조물의 축조가 활발히 진행되고 있다. 이를 설계하는데 있어서 무엇보다 중요한 것은 천해설계파 등과 같은 파랑변형계산을 얼마만큼 실현상과 근사시켜 재현할 수 있는지의 여부에 달려 있다. 지금까지의 천해설계파 산정에 있어서는 주로 단일 주파수와 단일 방향에 대한 규칙파해석이 수행되어져 왔으나, 실제해역에서의 파랑은 수많은 주파수와 파향, 파고들이 합성되어 이루어진 다방향 불규칙파랑이므로 실제 해역의 자연현상이 잘 표현되었다고 보기는 어렵다. (중략)

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1991.07a
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• pp.40-45
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• 1991

항만 건설, 매립, 임해 발전소의 걸선, 호안 축조 및 신공간 개발 등 연안역 개발시 설계 환경요소인 파랑을 정확히 예측함으로써 이러한 사업을 경제적으로 수행 할 수 있다. 특히 이들 구조물은 대부분 쇄파대내에 위치하므로 쇄파후의 파랑변형 및 Runup 등을 파악하여야 한다. 본 연구에서는 조파수조를 이용하여 쇄파후의 파고 및 Runup 등을 관측하여 경험식 및 해석해와 비교하였다.(중략)