• 한국지구과학회지
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• 제44권4호
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• pp.264-274
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• 2023

The Korea Strait comprises a continental shelf in a shallow sea that experienced glacio-eustastic sea-level changes during the Quaternary period. A long core of 76.6 m in length was acquired at the South Sea Drilling Project site (SSDP-101; 34°19.666'E and 128°16.335'N) with a 60 m water deep. The uppermost massive sand beds were interpreted as sandy sediments of the nearshore marine sand ridge in the shallow sea during the transgression of sea level, whereas the lower parts of alternating sandy and muddy beds were interpreted as deposits in marsh, estuary, and tidal flat environments. A three-layered geoacoustic model was reconstructed for the sedimentary succession in the high-resolution seismic profile based on a 140-grain size and sediment type of core SSDP-101. For the actual underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method.

• 한국항해항만학회지
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• 제41권6호
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• pp.451-466
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• 2017

원양어선 제501 오룡호는 황천 중인 베링해에서 조업 후 피항하던 중 개구부를 통한 침수로 인하여 침몰하였으며 많은 선원들이 사망하고 실종되었다. 본 연구에서는 유체-구조 연성(Fluid-Structure Interaction, FSI) 해석기법의 고도 정밀 M&S(highly advanced Modeling & Simulation) 시스템을 사용하여 실선 침수 침몰 시뮬레이션을 수행하여 침몰사고의 과정을 정확하고 과학적으로 분석하고자 하였다. 베링해 침몰사고 시의 기상 및 해상상태를 객관적으로 확보하기 위하여 침몰사고 지역의 시간대별 기상 및 해상 시뮬레이션을 수행하여 침몰사고 당시 파랑과 강풍 등을 분석하고, 불규칙 파랑과 강풍 스펙트럼을 사용하여 구현하였다. 사고선박의 선체 도면 등을 통하여 선박의 선형, 배치 및 중량 분포와 외부 해수 침수 개구부 및 선내 침수 경로를 분석하고 주요 탱크들의 용적과 그들의 중량 분포를 추정하여 침수 침몰 시뮬레이션을 위한 시나리오를 작성하고, 사고선박의 전선과 유체(공기 및 해수)를 상세 모델링을 하였다. 본 연구를 통하여 침수 침몰사고는 단순한 복원성의 부족으로 인한 일반적인 전복 침몰사고와는 다소 차이가 있다는 것도 확인할 수 있었다.

• 한국안전학회지
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• 제24권1호
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• pp.37-42
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• 2009

The present study is to estimate the effect of wave height affecting at the front face of breakwater systems, when a submarine trench is dredged in the distant offshore from outer breakwater. The wave diffraction field, which is important hydraulic factor in the ocean, is considered to be two dimensional(2D) plane and the configuration of the submarine trench on the sea bed designated by single horizontal long-rectangular system. The numerical simulation is performed by using Green function based on the boundary integral equation and meshed at moving boundary conditions. The results of present numerical simulations are illustrated by applying the normal incidence. It is shown that the ratios of wave height reduction at the front face of breakwater systems are approximately 20% by the effect of placing long trench on the sea bed. This study can effectively be utilized for safety assessment to various breakwater systems in the ocean field.

• 수산해양기술연구
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• 제51권4호
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• pp.600-613
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• 2015

The Fishing gear loss has been repeated every year in the West Sea; however, there has been no solution. So fisher men have undergone economic loss every year. Thus it is required to reduce the loss of fishing gear. In this study to find out the reason that the fishing gear is lost in the Sea, 10 years data of wave and current for 6 locations in the West Sea were investigated and a numerical modelling were conducted into the behaviour of a gillnet in wave and current. The fishing gear was modelled with the mass spring model. As a result, it came out into the open that the location where fishing gear loss occurred most frequently was Choongnam province. The height of the maximum significant wave in this province was 6.7 m and the period of that was 4.4 second. The maximum current speed was 0.7 m/s. As a result of simulation with these data, it was revealed that the buoy is one of the reasons to decrease the holding power of the gillnet. For example, the tension of anchor rope was decreased to 50% while the drag coefficient or volume of buoy was decreased to 25%. So it is predicted that an improvement of the buoy contributes to the reduction of the gillnet loss.

• 한국해안·해양공학회논문집
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• 제24권3호
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• pp.217-227
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• 2012

2007년 3월 31일에 영광을 비롯한 한반도 서해안에 발생한 이상파랑의 발생 원인을 관측자료와 수치모델을 이용하여 분석하였다. 사용된 자료는 조위 관측소에서 관측된 조위 자료와 AWS의 해면기압 자료로서 모두 1분 간격의 시계열 자료이다. 이러한 시계열 자료를 시간과 주기에 대한 에너지 성분으로 변환시켜줄 수 있는 웨이블렛 변환을 이용하여 이상파랑과 같이 단기적으로 불규칙하게 발생하는 변화를 분석하였다. 분석 결과를 이용하여 이상파랑의 도달시간과 진행방향을 도출하였고, 생성원인을 분석하기 위해 AWS 자료를 통해 기압 점프의 크기와 주기 및 진행방향에 대해 조사하였다. 3시간 간격의 분석일기도에 제시된 기압 분포를 이용하여 서해상에서 기압 점프의 이동 패턴을 유추하였다. 분석된 결과의 타당성을 검증하기 위해 2차원 수치모형을 이용하여 이상파랑에 대한 모의를 수행하였다. 기압 점프의 진행에 따라 발생된 해수면의 변동은 공진작용에 의해 수위가 증가하는 것으로 나타났다. 산정된 수위는 관측값과 비교할 때 과소 산정되는 것으로 나타났으나, 웨이블릿 변환을 통해 분석한 도달순서와 유사하게 수위 관측지역에 도달하는 것으로 산정되었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.624-637
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• 2019

A semi-submersible offshore platform always operates under complex weather conditions, especially wind and waves. It is vital to analyze the structural dynamic responses of the platform in short-term sea states under the combined wind and wave loads, which touches upon three following work. Firstly, a derived relationship between wind and waves reveals a correlation of wind velocity and significant wave height. Then, an Improved Mixture Simulation (IMS) method is proposed to simulate the time series of wind/waves accurately and efficiently. Thus, a wind-wave scatter diagram is expanded from the traditional wave scatter diagram. Finally, the time series of wind/wave pressures on the platform in the short-term sea states are converted by Workbench-AQWA. The numerical results demonstrate that the proposed numerical methods are validated to be applicable for wind and wave simulations in structural analyses. The structural dynamic responses of the platform members increase with the wind and wave strength. In the up-wind and wave state, the stresses on the deck, the connections between deck and columns, and the connection between columns and pontoons are relatively larger under the vertical bending moment. These numerical methods and results are wished to provide some references for structural design and health monitoring of several offshore platforms.

• 한국지구과학회지
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• 제43권4호
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• pp.520-531
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• 2022

The Yellow Sea experienced glacio-eustasy sea-level fluctuations during the Quaternary period. In the middle part of the Yellow Sea, the Quaternary successions were accumulated by alternating terrestrial, paralic, and shallow marine deposits that reflected the fluctuating sea levels. A long core of 69.2 m was acquired at the YMGR-102 site (33°50.1782'N and 123°48.3019'E) at a depth of 72.5 m in the middle of the Yellow Sea. A four-layered geoacoustic model was reconstructed for the sedimentary succession. It was based on seismic characteristics from 3.5 kHz SBP and air-gun seismic profiles and 96 grain-size properties in the core sample from YMGR-102. For the underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method. The geoacoustic model of YMGR-102 can contribute to the reconstruction of geoacoustic models, reflecting the vertical and lateral variability of the acoustic properties in the continental shelf of the middle Yellow Sea.

• 한국대기환경학회지
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• 제15권6호
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• pp.767-777
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• 1999

In the coastal region air flow changes due to the abrupt change of surface temperature between land and sea. So a numerical simulation for atmospheric flow fields must be considered the correct fields of sea surface temperature(SST). In this study, we used variables such as latent heat flux, sensible heat flux, short and long wave radiation of ocean and atmosphere which exchanged across the sea surface between atmosphere and ocean model. We found that this consideration simulated the more precise SST fields by comparing with those of the observated results. Simulated horizontal SST differences in season were 2.5~4$^{\circ}C$. Therefore we simulated the more precise atmospheric flow fields and the movement and dispersion of the pollutants with the Lagrangian particle dispersion model. In the daytime dispersion pattern of the pollutants emitted from ship sources moved toward inland, in the night time moved toward sea by land/sea breeze criculation. But air pollutants dispersion can be affected by inland topography, especially Yangsan and coastal area because of nocturnal wind speed decrease.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권1호
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• pp.1-8
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• 2011

In this paper, CFD simulation results for a tanker model are compared with experimental data over a range of wave conditions to verify a capability to predict the sea-keeping performance of practical hull forms. CFD simulations are conducted using WISDAM-X code which is capable of unsteady RANS calculations in arbitrary wave conditions. Comparisons are made of unsteady surface pressures, added resistance and ship motions in regular waves for cases of fully-loaded and ballast conditions of a large tanker model. It is shown that the simulation results agree fairly well with the experimental data, and that WISDAM-X code can predict sea-keeping performance of practical hull forms.

• 한국해양환경ㆍ에너지학회지
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• 제3권2호
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• pp.49-59
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• 2000

장전항 시설물의 최적설계를 위한 항내 파랑분포 수치 시뮬레이션을 수행하였다. 장전항 인근 해역의 바람자료에 기초한 극치동계해석에 의해 추정된 심해 설계파를 수치 시뮬레이션의 외해 경계조건으로 적용하였다. 파랑 시뮬레이션을 위해 Boussinesq 천해파 이론을 사용하였으며, 파의 분산성과 비선형성을 포함하였다. 해안 경계에 대해서는 파랑의 부분적인 반사가 가능토록 유공을 두거나, 파랑 에너지를 모두 흡수하는 해면층을 두어 모사하였다. 방파제 설계 파고를 산정하기 위해서 광역모델에 대한 시뮬레이션을 수행하였으며, 설계된 방파제 및 부두 배치에 대한 항내 정온도 해석을 위하려 상세모델에 대한 시뮬레이션을 수행하였다.