• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.4
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• pp.174-186
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• 1998

A Galerkin's finite element model incorporating infinite elements for modeling of radiation condition at infinity has been developed, which is based on an extended mild-slope equation. To illustrate the validity and applicability of the present model, the example analyses were carried out for a resonance problem in the rectangular harbor of Ippen and Goda (1963) and for wave transformations over circular shoals of Sharp (1968) and Chandrasekera and Cheung (1997). Comparisons with the results obtained by hydraulic experiments and hybrid element method showed that the present model gives very good results in spite of the rapidly varying topography. Numerical experiments were also performed for wave transformations over a circular concave well which may be an alternative to conventional wave barriers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.434-449
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• 2019

In this study, we develop a new cross-shore sediment module which takes the effect of infra-gravity waves of bound mode, and boundary layer streaming on the sediment transport into account besides the well-known asymmetry and under-tow. In doing so, the effect of individual random waves occurring during the unit observation period of 1 hr on sediment transport is also fully taken into account. To demonstrate how the individual random waves would affect the sediment transport, we numerically simulate the non-linear shoaling process of random wavers over the beach of uniform slope. Numerical results show that with the consistent frequency Boussinesq Eq. the application of which is lately extended to surf zone, we could simulate the saw-tooth profile observed without exception over the surf zone, infra-gravity waves of bound mode, and boundary-layer streaming accurately enough. It is also shown that when yearly highest random waves are modeled by the equivalent nonlinear uniform waves, the maximum cross-shore transport rate well exceeds the one where the randomness is fully taken into account as much as three times. Besides, in order to optimize the free parameter K involved in the long-shore sediment module, we carry out the numerical simulation to trace the yearly shoreline change of Mang-Bang beach from 2017.4.26 to 2018.4.20 as well, and proceeds to optimize the K by comparing the traced shoreline change with the measured one. Numerical results show that the optimized K for Mang-Bang beach would be 0.17. With K = 0.17, via yearly grand circulation process comprising severe erosion by consecutively occurring yearly highest waves at the end of October, and gradual recovery over the winter and spring by swell, the advance of shore-line at the northern and southern ends of Mang-Bang beach by 18 m, and the retreat of shore-line by 2.4 m at the middle of Mang-Bang beach can be successfully duplicated in the numerical simulation.

• Economic and Environmental Geology
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• v.25 no.2
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• pp.179-190
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• 1992

The Yeongchun area is located at the central part of the Danyang Coalfield, where Precambrian granitoids, Cambro-Ordovician Choseon Supergroup, Carboniferous-early Triassic Pyeongan Supergroup, middle Triassic-Jurassic Bansong Group and extrusive tuffs are exposed. The rocks in the area underwent four phases of deformation, which are (a) $D_1$ : Movement of the Okdong Fault, (b) $D_2$ : Formation of NW-SE trending folds and stretching lineations, (c) $D_3$: Movement of the Gagdong Thrust Fault and associated structures of NNE-SSW trending folds, and (d) $D_4$ : E-W trending strike-slip faults and folds. During the $D_3$-event, flexural slip deformation intensively affected rocks in the area. Strain measurements show relatively low strain intensity in the area. The types of strain ellipsoid are prolate in the hangingwall area and those near to the footwall area range from plane strain to weak oblate. The oblate type is developed in the region far from the footwall area.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.84-95
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• 1994

In recent years Jin-Beach and Hyeya River mouth have experienced severe erosion phenomena. The cause of erosion is examined using a 3-dimensional nunumerical sediment transport model. The model is composed of three components : wave model, wave-induced current model and 3-dimensional sediment transport model. In the wave analysis component we consider refraction, diffraction and reflection based on Maruyama and Kajima method. For the wave-induced current model we use depth-integrated continuty equation and momentum equations. For the 3-dimensional sediment transport model we consider bed load and suspended load simutaneously. Model results obtained for Jin-ha Beach and Hyeya River mouth agreed well with experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.195-198
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• 2011

석유 및 천연가스 생산에 사용되는 고정식 해양플랜트에는 자켓 구조물이 가장 많이 사용되고 있다. 생산에 사용되는 자켓 구조물은 풍하중이나 파랑하중에 의해 인명의 피해 없이 변위 및 응력에 대해 안전해야 한다. 그러나 1940년대 후반부터 사용되어 온 자켓 구조물은 피로하중, 노후화로 인해 내구성에 문제가 생기고 있다. 본 논문에서는 자켓 구조물의 안전성을 검토하기 위해 모드형상을 이용하여 자켓 구조물의 손상 위치를 탐색하는 방법을 제시한다. 제시한 손상탐지기법의 효용성을 입증하기 위해 자켓 구조물의 유한요소모델에 임의의 손상을 모사하였다. 유한요소모델의 손상 전 모드형상과 손상 후 모드형상의 모달 변형에너지의 변화를 이용하여 손상 지수를 유도하고 유도한 손상지수를 사용하여 손상이 있는 부재와 손상이 없는 부재를 분류하였다. 연구 결과 손상지수가 '0'인 부재를 제외한 나머지 부재 모두 본 연구에서 제시한 손상탐지기법으로 손상 부재를 판별할 수 있었다.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.52.1-52.1
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• 2010

본 연구에서는 자유수면 흐름을 해석할 수 있는 연직방향에 대해 좌표변환된 3차원 동수압 모형을 제시하였다. 제시한 모형은 자유수면파 동수압의 해석을 위하여, 2중 예측-수정(double predictor-corrector)방법을 적용하였다. 본 연구에서는 자유수면과 동수압을 고려하기 위하여 자유수면 보정단계와 동수압 보정단계로 나누어 정확한 동역학적 경계조건을 적용하는 방법을 제시하였고, 제시한 모형을 이용한 수치모의 결과를 검증하기 위하여 타원형 천퇴에 의한 파의 변형에 대한 수치모의를 실시하였다. 전반적으로 수치모의 결과는 실험자료와 일치하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.84-90
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• 1993

Iterative solution procedure (Conjugate Gradient Method, Panchang et al., 1991) is implemented for solving the complete mild slope equation for the spherical shoal and the coast with detached breakwater. The numerical results agreed well with the experimental data. The disadvantage that mild slope eguation could be solved only for small domains is now overcome by using this solution procedure. Moreover it can be easily applied to the coastal regions with complex geometry and structures, and needs not so much computer time as the conventional models.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.81-91
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• 1993

Studies on the flow pattern due to reclamation in the Myunggi-Nocksan region are carried out based on field observations and numerical experiments. Serial time series measurement of current, temperature and salinity were conducted for 1 tidal period at intervals of 1 hour from surface to bottom on station located at 128.deg. 54' 44" E, 35.deg. 01' 04" N in April and June 1992. Surface current opposite to the subsurface current causes turbulent mixing to make homogeneous salinity pattern in vertical section. Reclamation has little effect on the wave pattern and flow patterns are also nearly similar except on the nearby region of reclamation where flow speed somewhat weakened.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.260-265
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• 1994

A new set of elliptic wave equations describing the deformations of irregular waves on a large-scale current field in water of irregular depth is given, and using finite difference scheme an efficient numerical method is also presented. The elliptic equations are solved in a similar way to Initial value problem. This method is extensively used for the calculation of wave spectral transformation. and computation results agree very well with experimental data (Hiraishi, 1991). Finally numerical examples are presented concerning the interactions between waves and currents over a mildly sloping beach and also over a mound.

• Journal of Korean Port Research
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• v.8 no.1
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• pp.41-47
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• 1994

The present paper discusses the nonlinear wave deformation due to a submerged coastal structure. Theory is based on the frequency-domain method using the third order perturbation and boundary integral method. Theoretical development to the second order perturbation and boundary integral method. Theoretical development to the second order Stokes wave for a bottom-seated submerged breakwater to the sea floor is newly expanded to the third order for a submerged coastal structure shown in Figure 1. Validity is demonstrated by comparing numerical results with the experimental ones of a rectangular air chamber structure, which has the same dimensions as that of this study. Nonlinear waves become larger and larger with wave propagation above the crown of the structure, and are transmitted to the onshore side of the structure. These characteristics are shown greatly as the increment of Ursell number on the structure. The total water profile depends largely on the phase lag among the first, second and third order component waves.