• 한국해양공학회지
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• 제19권4호
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• pp.9-14
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• 2005

In the present paper, the wave absorbing performance of the fully submerged horizontal porous plates has been investigated, numerically and experimentally. The submerged porous system is composed of multi-layered horizontal porous plates that are clamped at the vertical setwall, which are slightly inclined and placed vertically, in parallel, with spacing. The hydrodynamic interaction of incident waves with the rigid porous multi-layered plates was formulated within the context of linear wave-body interaction theory and Darcy's law. In order to validate the effectiveness of the present computing code, the numerical results were compared with the analytical and experimental results. It is found that triple horizontal porous plates with slight inclination, if properly tuned for wave energy dissipation against the standing waves in front of the vertical wall, can have high performances in reducing the reflected wave amplitudes against the incident waves over a wide range of wave frequency.

• 한국해양공학회지
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• 제16권5호
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• pp.1-6
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• 2002

Extreme waves are generated in a model basin based on directional wave focusing. The targeted wave field is described by double summation method and it is applied to serpent-type wavemaker system. The extreme crest amplitude at a designed location is obtained by syncronizing the phases and focusing the directions of wave components. Two distinguished spectrums of constant wave amplitude and constant wave steepness are adapted to describe the frequency distribution of component waves. The surface profile of generated wave packets is measured by wave guage array and the effects of dominant spectral parameters governing extreme wave characteristics are investigated. It is found that frequency bandwidth, center frequency, shape of frequency spectrum and directional range play a significant role in the wave focusing. In particular, the directional effect significantly enhances the wave focusing efficiency.

• Journal of Advanced Research in Ocean Engineering
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• 제4권2호
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• pp.53-65
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• 2018

The load condition significantly influences ship maneuverability in calm water. In this research, the effect of the load condition on turning performance of a very large crude oil carrier (VLCC) sailing in adverse weather conditions is investigated by an MMG-based maneuvering simulation method. The relative drift direction of the ship in turning to the wave direction is $20^{\circ}-30^{\circ}$ in ballast load condition (NB) and full load condition (DF) with a rudder angle $35^{\circ}$ and almost constant for any wind (wave) directions. The drifting displacement in turning under NB becomes larger than that under DF at the same environmental condition. Advance $A_d$ and tactical diameter $D_t$ become significantly small with an increasing Beaufort scale in head wind and waves when approaching, although $A_d$ and $D_t$ are almost constant in following wind and waves. In beam wind and waves, the tendency depends on the plus and minus of the rudder angle.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.63-68
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• 2000

A very large floating structure has rather small motion characteristics as to the whole body, while the motion at end part of such structure becomes largest due to the elastic motion of the structure. This paper presents on the theoretical result on the relative motion characteristics and green water phenomena of VLFS in waves This phenomena affect not only to strength of the structure but also the determination of depth of structure. To predict motion responses of structure in regular waves, the source-dipole distribution method and F.E.M is used By irregular wave results, the probability of occurrence of green water and response of the structure were calculated.

• 한국해양공학회지
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• 제9권1호
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• pp.161-172
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• 1995

A numerical procedure is described fro predicting the motion and structural responses of tension leg platforms(TLPs) in waves. The developed numerical approach is based on a combination of a three dimensional source distribution method and the dynamic response analysis method, in which the superstructure of TLPs is assumed flexible instead of the rigid body assumption used in tow-step analysis method. Both the hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural whole structure are formulated using element-fixed coordinate systems which have the origin at the node of the each hull element and move parallel to a space-fixed coordinate system. Numerical results are compared with the experimental and numerical ones, which are obtained in the literature, concerning the motion and structural responses of a TLP in waves. The results of comparison confirmed the validity of the proposed approach.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권3호
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• pp.277-300
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• 2016

The motion of a floating body and the free surface flow are the most important design considerations for ships and offshore platforms. In the present research, a numerical method is developed to simulate the motion of a floating body and the free surface using a fixed rectilinear grid system. The governing equations are the continuity equation and Naviere-Stokes equations. The boundary of a moving body is defined by the interaction points of the body surface and the centerline of a grid. To simulate the free surface the Modified Marker-Density method is implemented. Ships advancing in regular waves, the interaction of waves by a fixed circular cylinder array and the response amplitude operators of an offshore platform are simulated and the results are compared with published research data to check the applicability. The numerical method developed in this research gives results good enough for application to the initial design stage.

• 한국해양공학회지
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• 제23권1호
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• pp.31-37
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• 2009

Coastal vegetation consists of rooted flowering marine plants that provide a variety of ecosystem services to the coastal areas they colonize. The attenuation of currents and waves and sediment stabilization are often listed among these services. From this point of view, artificial seaweed is an effective method of controlling sea bed sediment and stabilization without damaging the landscape or the stability of the coastline. A series of hydraulic experiments were performed in a wave channel with regular and irregular waves to examine the effect of artificial seaweed in relation to scouring and beach erosion prevention. Based on the results of these experiments, the coastal vegetation model is efficient against scouring and beach erosion.

• Journal of Ship and Ocean Technology
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• 제5권4호
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• pp.29-43
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• 2001

In this paper, free surface flows around an advancing two-dimensional rectangular cylinder piercing the free surface are studied using numerical and experimental methods. Especially, wave breaking phenomenon around the cylinder is treated in detail. A series of numerical simulations and experiments were performed for the purpose of comparison. For the numerical simulations, a finite difference method was adopted with a rectangular grid system, and the variation of the free surface was computed by the marker density method. The computational results are compared with the experiments. It is confirmed that the present numerical method is useful for the numerical simulation of nonlinear free surface waves around a piercing body.

• 한국해안해양공학회지
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• 제5권2호
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• pp.58-65
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• 1993

풍파가 그 생위영역을 벗어나 전이해 갈 경우 스펙트럼의 폭은 side band instability 등으로 인해 증가하게 되는데 이 경우 비선형불규칙파의 추계학적 성질에 대해서는 거의 규명된 바 없으나 간략화된 Longuet-Higgins의 파랑모형을 토대로 비선형 불규칙파의 파봉에 대한 확률밀도함수를 유도하였으며 모의 결과 스펙트럼 폭이 peak의 분포에 지대한 영향을 미치며 비선형의 정도가 심화될 경우 유의파고는 증가하는 것으로 밝혀졌다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.85-89
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• 2004

The wave interactions with fully submerged and floating dual buoy/vertical porous membrane breakwaters has been investigated in experimentally to validate the developed theory and numerical method in the previous study, in which multi-domain hydro-elastic formulation was carried out in the context of linear wave-body interaction theory and Darcy's law. It is found that the experimental results agrees well with the numerical prediction. Transmission and reflection can be quite reduced simultaneously especially in the region of long waves. The properly tuned system to incoming waves can effectively dissipate wave energy and also offset each other between incident and scattered waves using its hydro-elasticity and geometry.