• 대한조선학회논문집
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• 제39권4호
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• pp.24-31
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• 2002

계류된 FPSO와 DP로 위치를 유지하는 셔틀탱커에 있어 장주기 표류운동의 특성은 매우 중요하다. 장주기 공진 운동 해석에 있어 표류감쇠력의 중요성은 아무리 강조해도 지나침이 없으나 감쇠력 발생의 원인이 너무도 다양하기 때문에 아직까지 이론에 의해 정확한 감쇠력을 추정하기가 어렵다. 따라서 모형시험을 통한 표류감쇠력을 이용하는 것이 시뮬레이션에서 장주기 운동예측치의 신뢰성을 높이는 방법이다. 본 논문에서는 FPSO, 셔틀탱커 등의 표류감쇠력의 실험 예측치를 구하기 위해 탱커 선형의 장주기 표류운동 감쇠력을 계측하였다. 파도, 바람, 조류 등에 의한 영향을 살펴보았으며 추진기 작동유무에 따른 장주기 운동감쇠력의 변화를 고찰하였다.

• 한국해양공학회지
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• 제14권4호
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• pp.17-22
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• 2000

As the offshore oil fields are moved to the deep ocean, the oil production system of FPSO(Floating Production Storage and Offloading System) Type are constructed frequently these days. So, it is very important to estimate the drift motion and damping effects due to the drift motion simultaneously. The components of slow drift motion damping consist of viscous, wave radiation effect and wave drift damping. It is needed to estimate the wave drift damping more accurately than others. The wave drift damping signifies the time-rate of mean wave drift force on oscillating ship or ocean structure which constant speed. In order to calculate this, the 3-Dimensional panel method is employed with the translating and pulsating Green function in the frequency domain. The calculation is carried out for a Series 60 ($C_B$/=0.7) and the results are compared with other numerical ones.

• 한국해안해양공학회지
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• 제13권3호
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• pp.195-201
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• 2001

본 논문은 파랑중에 다전 계류된 원유저장선에 대한 저주파수 운동을 수치 모사하였다. 시간영역에서의 운동방정식은 충격응답함수를 포함하여 수평면상의 운동 즉 전후, 좌우 및 선수 운동을 고려하였다. 시간영역의 운동방정식에 나타난 부가질량, 파랑감쇠계수, 1차항 파랑 강제력 그리고 2차항 파랑 강제력을 주파수 영역의 특이점 분포법을 사용하여 계산하였고, 다점 계류된 계류삭은 체인이 해저면에 닿은 운동 효과를 포함하여 준 정적 현수선 이론으로 산정되었다. 계산 예로서 장파정 불규칙 파랑 중에 놓인 바아지식 원유저장선에 대한 시간 영역 해석을 수행하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.222-227
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• 2001

The time simulation of slow drift motions of moored FPSO in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and are consisted of horizonal plane -surge, sway and yaw. The added mass coefficients, wave damping coefficients, first order wave exciting forces and the second order wave drift forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The mooring lines are modeled quasistatically as catenary for chains and touchdown. As for numerical example, time domain analyses are carried out for a box-type FPSO in long crest irregular wave condition.

• 한국해양공학회지
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• 제18권3호
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• pp.8-12
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• 2004

The anchor is laid on the seabed, and the main engine is working against incident environmental loads in a typhoon. As the main engine is broken Mum in the storm, the anchor chain is cut and the vessel drifts. Although a ship is moored by two-point mooring lines to maintain her position, it has crashed into a rock because of a typhoon, resulting in a possible accidental oil spillage. In this paper, we studied maintenance of a ship's position, which is analyzed based on the slow motion maneuvering equations considering wave, current, and wind. To estimate wave loads, the direct integration method is employed. The current forces are calculated, using MMG (Mathematical Modeling Group). Th two-point mooring forces are quasi-statistically evaluated, using the catenary equation. Th coefficients of wind forces are modeled from Isherwood's empirical data, and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two-point moored ship are simulated, considering wave, current, and wind load, in specific domain of time.

• 대한조선학회지
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• 제27권4호
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• pp.3-14
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• 1990

해상에 계류된 부유체에 좁은 폭의 스펙트럼을 갖는 파가 입사하게 되면 부유체는 두 가지의 대조적인 주기를 갖고 운동을 한다. 이 운동중 장주기 성분의 주기는 계류된 부유체의 수평방향 고유주기와 같은 정도의 크기여서 유발되는 대진폭 수평 변위는 계류삭에 심각한 응력을 발생시키므로 이에 대한 해석이 필요하다. 본 연구에서는 다척도전개기법(Multiple-Scale Expansion Method)을 시간과 길이에 적용하여 부유체의 운동은 선형 1차 조화 문제와 선형 장주기 문제의 2가지 선형 문제로 표현될 수 있음을 보였다. 따라서 임의 형상을 지닌 3차원 부유체의 대진폭 표류 운동은 2차 포텐셜문제를 풀지않고 해석될 수 있음을 입증하였다. 아울러 장주기 표류운동에 수반되어 장파가 발생함을 보였으며 장주기 운동과 관련되는 감쇠력에 대해서도 고찰하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.232-236
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• 2003

The anchor is laid on seabed and the main engine is worked to against incident environmental loads in typoon. As the main engine is broken down in the storm, the anchor chain is cutted and the vessel is drifted. Although a ship is moored by two point mooring lines to keep the her position, a ship is crashed into a rock because of typoon and the accident of oil spilling may be occured. In this paper, we studied the position-keeping of a ship which is analyized based on the slow motion maneuvering equations considering wave, current and wind. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical of MMG. The two point mooring forces are quasisatatically evaluated by using the catenary equation. The coefficeints of wind forces are modeled from Isherwood’s emperical data and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two point moored ship are simulated considering wave, current, wind load in time domain.

• 한국해양공학회지
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• 제17권4호
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• pp.8-15
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• 2003

When a typoon sets into harbour, a moored ship shows erratic motions and even mooring line failure may occur. such troubles may be caused by harbour resonance phenomena, resulting in large motion amplitudes at low frequency, which is close ti the natural frequency of th moored ship. The nonlinear motions of a ship moored to quay are simulated under external forces due to wave, current including mooring forces in time domain. The forces due to waves are obtained from source and dipole distribution method in the frequency domain. The current forces are calculated by using slow motion maneuvering equation in the horizontal plane. The wind forces are calculated from the empirical formula of ABS and the mooring forces of ropes and fenders are modeled as linear spring.

• 대한조선학회논문집
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• 제41권1호
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• pp.8-14
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• 2004

As the number of offshore structure is glowing in deep waters, there have been increased damages of it. These floating structures in offshore locations exposed to harsh environmental conditions. In recent years, there has been a slowing attention around damages on bow and deck on FPSO caused by waves in steep storm condition. This paper describes a study of the water on deck due to the dynamic behavior of a FPSO with turret mooring system. The nonlinear motions of the FPSO are simulated under external forces due to wave, current, wind, and mooring forces in the time domain. The direct integration method is employed to estimate low frequency drift wave forces. The current forces are calculated by using slow motion maneuvering equations in the horizontal plane. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A.

• Ocean Systems Engineering
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• 제1권4호
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• pp.297-315
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• 2011

New applications of streamlined Autonomous Underwater Vehicles require an AUV capable of completing missions with both high-speed straight-line runs and slow maneuvers or station keeping tasks. At low, or zero, forward speeds, the AUV's control surfaces become ineffective. To improve an AUV's low speed maneuverability, while maintaining a low drag profile, through-body tunnel thrusters have become a popular addition to modern AUV systems. The effect of forward vehicle motion and sideslip on these types of thrusters is not well understood. In order to characterize these effects and to adapt existing tunnel thruster models to include them, an experimental system was constructed. This system includes a transverse tunnel thruster mounted in a streamlined AUV. A 6-axis load cell mounted internally was used to measure the thrust directly. The AUV was mounted in Memorial University of Newfoundland's tow tank, and several tests were run to characterize the effect of vehicle motion on the transient and steady state thruster performance. Finally, a thruster model was modified to include these effects.