• 해양환경안전학회지
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• 제19권1호
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• pp.78-84
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• 2013

본 연구의 주목적은 쌍동선형의 조파저항성능을 평가할 수 있는 수치해석 프로그램을 개발하는 것이다. 개발된 프로그램을 이용하여 비대칭과 대칭인 단동선형을 가진 서로 다른 두 가지 쌍동선에 대하여 수치계산을 수행하여 저항성능을 평가 하였다. 타당성 검증을 위해서 수치해석 결과 중 선수와 선미에서의 침하량, 트림 그리고 조파저항 계수를 수조모형시험 결과와 비교하였다. 이러한 비대칭 그리고 대칭 선형이 가지는 쌍동선의 유체역학적 특성에 관한 비교분석 자료는 향후 선형개발 시 충분한 활용 가치가 있다고 판단된다.

• 한국해양공학회지
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• 제32권6호
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• pp.458-465
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• 2018

Ice-going ships such as icebreakers, icebreaking tankers, and icebreaking LNG carriers are subjected to wave loads in open water and ice loads in ice-covered water. In terms of the ship's structural design, the local ice load is important. The fatigue failure due to repeated ice loads is also important. ISO 19906 specifies the assessment of the fatigue limit for a polar offshore structures. In addition, Lloyd's Register refers to fatigue damage based on ShipRight FDA ICE. In ShipRight FDA ICE, the fatigue damage indices due to wave and ice loads are simply presented as 0.5 for each load. It also states that the sum of the two fatigue damage indices should not exceed one. This study calculated and analyzed the fatigue damage index and fatigue life considering ARAON's voyage schedules and the assumed Antarctic voyage based on data measured during the Arctic voyage of ARAON in 2010.

• Ocean Systems Engineering
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• 제3권1호
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• pp.35-53
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• 2013

In this study, a hybrid floating structure with cylinder was introduced to reduce the hydrodynamic motions of the pontoon type. The hybrid floating structure is composed of cylinders and semi-opened side sections to penetrate the wave impact energy. In order to exactly investigate the hydrodynamic motions and structural behavior of the hybrid floating structure under the wave loadings, integrated analysis of hydrodynamic and structural behavior were carried out on the hybrid floating structure. Firstly, the hydrodynamic analyses were performed on the hybrid and pontoon models. Then, the wave-induced hydrodynamic pressures resulting from hydrodynamic analysis were directly mapped to the structural analysis model. And, finally, the structural analyses were carried out on the hybrid and pontoon models. As a result of this study, it was learned that the hybrid model of this study was showed to have more favorable hydrodynamic motions than the pontoon model. The surge motion was indicated even smaller motion at all over wave periods from 4.0 to 10.0 sec, and the heave and pitch motions indicated smaller motions beyond its wave period of 6.5 sec. However, the hybrid model was shown more unfavorable structural behavior than the pontoon model. High concentrated stress occurred at the bottom slab of the bow and stern part where the cylinder wall was connected to the bottom slab. Also, the hybrid model behaved with the elastic body motion due to weak stiffness of floating body and caused a large stress variation at the pure slab section between the cylinder walls. Hence, in order to overcome these problems, some alternatives which could be easily obtained from the simple modification of structural details were proposed.

• 해양환경안전학회지
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• 제18권2호
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• pp.153-159
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• 2012

본 연구에서는 실습선의 다방향 불규칙파중 종방향 운동응답특성을 선형 스트립이론에 기초한 상용코드(MAXSURF v.16)를 이용하여 해석하였다. 해석에 앞서 상용코드의 검증을 위해 파나막스급 컨테이너선에 대해 실험조건과 동일한 선형과 해석조건을 적용하여 계산한 결과와 기 계산된 결과(Flokstra, 1974)가 상호 유사한 경향을 얻어 해석의 신뢰성을 확보하였다. 계산조건으로는 Fn=0.257에서 파랑외력을 ITTC 파스펙트럼에 기초한 뷰포트 스케일 5($\bar{T}=5.46$, $H_{1/3}=2m$)의 파스펙트럼을 산출하였고, 조우각은 선수사파(Head & bow seas, $150^{\circ}$)를 적용하여 상하동요(Heave)와 종동요(Pitch)의 선체운동응답스펙트럼을 해석하였다. 다방향 불규칙파에 대한 운동응답스펙트럼은 선수사파에서 상하동요의 경우는 미소하게 단파정파에서 높은 스펙트럼 분포를 보이고 종동요의 경우는 장파정파에서 높게 나타났다.

• 대한조선학회논문집
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• 제51권6호
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• pp.503-509
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• 2014

This paper describes the time-domain numerical method for prediction of slamming loads on a ship in waves using the strip theory. The slamming loads was calculated considering the relative vertical velocity between the instantaneous ship motion and wave elevation. For applying the slamming force on a ship section, the momentum slamming theory and the empirical formula-based bottom slamming force were used corresponding to the vertical location of wetted body surface. Using the developed method, the vertical bending moments, relative vertical velocities, and impact forces of S175 containership were compared in the time series for various section locations and wave conditions.

• 한국해양공학회지
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• 제29권4호
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• pp.300-308
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• 2015

With the increases in oil and gas prices, and energy consumption, drillship construction has increased during the last decade. A drillship using a dynamic positioning (DP) system to maintain its position and heading angle during drilling operations. In addition, a drillship is equipped with a moonpool structure to allow its drilling systems to be operated in the midship section. A drillship for the North Sea is specially designed to endure harsh environmental loads. For safe operation in the North Sea, the drillship should have good motion response and robust hull strength. A break water should be considered on the bow and side deck to prevent the green water on deck phenomenon from incoming waves. In addition, the moonpool should be designed to reduce the speed loss and resonance motion. In this study, the hydrodynamic characteristics of a drillship for the North Sea were examined in relation to the motion, wave loads, green water, and moonpool resonance in the initial design stage.

• 대한조선학회논문집
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• 제47권2호
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• pp.188-195
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• 2010

Green water load is an important parameter to be considered in designing a modern ship or offshore structures like FPSO and FSRU. In this research, a numerical simulation method for green water phenomenon is introduced. The Navier-Stokes equations and the continuity equation are used as governing equations. The equations are calculated using Finite Difference Method(FDM) in rectangular staggered grid system. To increase the numerical accuracy near the body, the Cartesian cut cell method is employed. The nonlinear free-surface during green water incident is defined by Marker-density method. The green waters on a box in regular waves are simulated. The simulation results are compared with other experimental and computational results for verification. To check the applicability to moving ship, the green water of the ship which is towed by uniform force in regular wave, is simulated. The ship is set free to heave and to surge.

• 한국해양공학회지
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• 제20권2호
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• pp.66-71
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• 2006

To develope a hull form of catamaran type dredging vessel, resistance characteristics is investigated to find the interaction effect of waves between the two hulls. Re fore body shape is simplified as two dimensional wedge shape for the maintenance and disassembly/assembly. Based on MAC method, numerical simulation is performed in staggered variable mesh system. Re conservation form of Euler equations and continuity equation are applied as governing equations. To verify numerical methods, the wive patterns along the hull surface are compared with the results of model tests. This study is performed as varying wedge shape of the bow and the distance between the two hulls. The wave interaction between two hulls are observed to investigate the relation the resistance performance and the flow characteristics. Suitable hull form and distance between two hulls are discussed.

• 한국항해항만학회지
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• 제28권8호
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• pp.753-757
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• 2004

선미파의 점성 상호작용과 수중고속선의 sub-breaking 현상을 해석하기 위하여 자유표면 유통을 수치적으로 시뮬레이션하였다. Navier-Stokes 방정식을 풀었으며 유한차분법, 물체적합좌표계, 벽법칙, 삼중격자법을 적용하였다. S-103 모형을 대상으로 준쇄파의 수치결과를 실험과 비교하였고 준쇄파 발생조건을 수중 고속선인 3차원 회전체에 대해 적용하였다. 준쇄파 해석결과에 의하면 M/Us 구배가 잠김 깊이에 영향을 미치고 있음을 알 수 있었다. 또한 선수파가 박리에 영향을 미쳐 선미파를 변형시킴을 확인하였다.

• 대한조선학회논문집
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• 제43권1호
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• pp.1-14
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• 2006

To improve maritime safety, it is very important not only to make safer design and operation but also to do proper response in case of maritime casualty. The large-scaled casualties will be caused by loss of structural strength and stability due to the progressive flooding and enlargement of damage by the effect of waves and wind. To prevent foundering and structural failure, the prediction of ship motion behavior of damaged ship in wave is necessary. This paper describes the motion behavior of damaged ship in waves through theoretical and experimental studies. A time domain theoretical model of damaged ship motions and accidental flooding, which can be applied to any type of ship or arrangement and considers the effects of flooding of compartments, has been developed. The model tests have been carried out in regular and irregular waves with different wave heights and directions in ship motion basin. Those were performed for three different damaged conditions such as engine room bottom damage, side shell damage and bow visor damage of a Ro-Ro ship. Comparison of theoretical and experimental results was performed.