• Journal of Ship and Ocean Technology
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• 제7권1호
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• pp.29-35
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• 2003

Intensive experimental investigation has been conducted on the characteristics of model tank with intruded flow. The remaining flow inside tank contribute to the dynamic behavior and further closely related to the stability of vessel as well. To understand the importance of the trapped flow and its dynamic effects a series of systematic tests were conducted using a bench tester that could generate periodic roll motion and also complex motions of combined roll-heave-sway. To accommodate experimental conditions and to create three degree freedom of motions, a bench tester was fabricated and verified. Having similarities in terms of flow trapped inside tank, theoretical approaches for A.R.T. were applied to the study. The major parameters including roll angle, period and flow height were varied in the experiments to obtain the characteristics of model tank.

• 수산해양기술연구
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• 제59권4호
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• pp.336-343
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• 2023

The aging fishery training vessels from the past have mostly been decommissioned, and many universities are introducing state-of-the-art large fishery training vessels. The purpose of these training vessels is to train marine professionals and above all, safety to prevent marine accidents should be of utmost priority as many students embark on the vessel. This study estimated the impact of the hydrodynamic interaction forces acting on the model vessel (fishery training vessel) from the bank when the vessel pass near the semi-circle bank wall in various conditions through the numerical calculation, especially concerning maneuvering motions of the vessel. For estimation, variables were mainly set as the size of the semi-circle shape, the lateral distance between the bank and the model vessel, and the depth near the bank. As a result, it was estimated that, in order for the model vessel to safely pass the semi-circle bank wall at a speed of 4 knots, the water depth to the vessel draft ratio should be 1.5 or more (approximately 8 m of water depth), and the lateral distance from the semi-circle bank wall should be 0.4 times the model vessel's length (L_pp) or more (a distance of 34 m or more). Under these conditions, it was expected that the model vessel would pass without significantly being affected by the bank wall.

• Ocean Systems Engineering
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• 제3권2호
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• pp.137-147
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• 2013

Moonpools are vertical wells in a floating body used onboard many types of vessels like cable-laying vessels and offshore support vessels. Moonpool gives passage to underwater activities for different types of ships as per their mission requirements. It is observed that inside a moonpool considerable relative motions may occur, depending on shape, depth of the moonpool and on the frequency range of the waves to which the ship is exposed. The vessel responses are entirely different in zero and non-zero Froude number. Former situation is paid attention in this study as the mission requirement of the platform is to be in the particular location for long period of operation. It is well known that there are two modes of responses depending on the shape of the moonpool viz., piston mode for square shape and sloshing mode for rectangular shapes with different aspect ratios of opening like 1:1.5 and 1:2 ratios. Circular shaped moonpool is also tested for measuring the responses. The vessel moored using heavy lines are modeled and tested in the wave basin. The moored lines are provided with pre-tension and the dynamic tensions on the lines are measured. The different modes of oscillations of water column are measured using wave gauge and the vessel response at a particular situation is determined. RAOs determined for various situations provide better insight to the designer. The experiments done in the wave basin may also be compared with a software package meant for handling moored floating bodies.

• 동력기계공학회지
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• 제18권4호
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• pp.112-116
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• 2014

Roll and pitching motions of a vessel can seriously degrade the performance of mechanical systems and the effectiveness of personnel. Many studies on roll stabilization and trimming control system design have focused on stabilizing the vessel through the use of fins, tanks, rudders and flaps. However the ultimate objective of such approaches must be to improve boarding sensitivity. This paper presents an anti-seasickness bed that consists of a rotator and bearing system that does not make use of electric power. The advantages of this system are its simple construction, usefulness, and safe operation. In this study, the rotation angles of the upper plate of a bed according to change weight of the rotator have been calculated to determine the stability. As a result, it can be concluded that proposed stabilizing bed can be of practical use in the field.

• 대한조선학회지
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• 제26권2호
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• pp.32-40
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• 1989

자동위치 확보시스템은 선박이 불규칙 해상에서 작업을 수행할 때 선체의 위치 및 선수를 일정한 작업반경 내에서 유지할 수 있도록 추진기를 자동제어하는 방법이다. 위치확보시스템의 구성은 계측시스템, 제어기시스템, 추진기시스템 및 동력시스템으로 구성된다. 본 논문은 최적제어 기법과 필터링 기법을 이용한 제어기시스템 구성에 관하여 논하였고, 제어시스템 구성을 위한 상태방정식의 정립과정을 서술하였다. 선체의 평면운동은 저주파수 운동과 고주파수 운동의 성분으로 구성되었다고 가정하였다. 저주파수 운동은 추진기에 의한 외력, 조류력 및 2차차수 파랑강제력에 기인하며 고주파수 운동은 1차 차수 파랑강제력에 의해 유기된다. 해상에서 계측되는 신호에는 선체의 운동성분 이외에도 계측오차 성분이 포함된다. 자기동조필터 및 칼만필터를 이용하여 계측신호로부터 저주파수 운동성분과 고주파수 운동성분을 각각 독립적으로 추정하고, 추정된 저주파수 운동성분을 궤환하여 제어를 수행하였다. 제어기는 교란환경 속의 최적제어기인 LQG제어기를 이용하였다. 시뮬레이션을 수행하기 위하여 Wimpey Sealab의 데이타를 이용하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2023년도 추계학술대회
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• pp.242-243
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• 2023

소형선박 운항은 해양 환경 및 기상조건에 따라 선박이 파도에 대해 다양한 방향으로 입사각을 가지게 된다. 특히 소형선박의 경우 입사각에 따라 운동의 특성이 크게 달라지며 이는 안정성과 밀접한 관계가 있다. 본 연구는 불규칙파에서 소형선박이 운항 중일 때 입사각에 따른 운동특성을 시뮬레이션과 실험을 통하여 비교분석 하였다. 불규칙파는 실제 소형선박이 운항하는 연안의 파랑 데이터를 바탕으로 만들었다. 선속에 따라 선박의 횡요동요를 분석하였으며 선속이 느릴 때에는 선수사파에서 가장 큰 횡요동요가 발생하였으며 선속이 빨라짐에 따라 선수사파의 횡요동요는 감소하나 선미사파의 횡요동요가 커지는 것을 알 수 있다. 따라서 선속에 따른 입사파 각도를 변경하여 선박의 운항할 경우 선박의 안정성과 운항 효율성을 개선할 수 있을 것이다.

• International Journal of Ocean System Engineering
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• 제3권4호
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• pp.175-187
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• 2013

Moonpools are vertical wells in a floating body used onboard many types of vessels like Exploration and drilling vessels, Production barges, Cable-laying vessels, Rock dumping vessels, Research and offshore support vessels. Moonpool gives passage to underwater activities for different types of ships as per their mission requirements. It is observed that inside a moonpool considerable relative motions may occur, depending on shape, depth of the moonpool and on the frequency range of the waves to which the ship is exposed. The vessel responses are entirely different in zero and non-zero Froude number. Former situation is paid attention in this study as the mission requirement of the platform is to be in the particular location for long period of operation. It is well known that there are two modes of responses depending on the shape of the moonpool viz., piston mode for square shape and sloshing mode for rectangular shapes with different aspect ratios of opening like 1:1.5 and 1:2 ratios. Circular shaped moonpool is also tested for measuring the responses. The vessel moored using heavy lines are modelled and tested in the wave basin. The pretensions of the lines are varied by altering the touchdown points and the dynamic tensions on the lines are measured. The different modes of oscillations of water column are measured using wave gauge and the vessel response at a particular situation is determined. RAOs calculated for various situations provide better insight to the designer.

• Journal of Ship and Ocean Technology
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• 제8권3호
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• pp.26-39
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• 2004

A vessel/mooring/riser coupled dynamic analysis program in time domain is developed for the global motion simulation of a turret-moored, tanker based FPSO designed for 6000-ft water depth. The vessel global motions and mooring tension are simulated for the non-parallel wind-wave-current 100-year hurricane condition in the Gulf of Mexico. The wind and current forces and moments are estimated from the OCIMF empirical data base for the given loading condition. The numerical results are compared with the OTRC(Offshore Technology Research Center: Model Basin for Offshore Platforms in Texas A&M University) 1:60 model-testing results with truncated mooring system. The system's stiffness and line tension as well as natural periods and damping obtained from the OTRC measurement are checked through numerically simulated static-offset and free-decay tests. The global vessel motion simulations in the hurricane condition were conducted by varying lateral and longitudinal hull drag coefficients, different mooring and riser set up, and wind-exposed areas to better understand the sensitivity of the FPSO responses against empirical parameters. It is particularly stressed that the dynamic mooring tension can be greatly underestimated when truncated mooring system is used.

• 해양환경안전학회지
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• 제13권2호
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• pp.147-153
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• 2007

이 연구의 목적은 부산항에 입항하는 대형 컨테이너 선박의 안전 접안 조종을 위한 한계풍속을 설정하는데 있다. 계산결과, 정상풍속 13.5m/sec 이하의 바람에서는 예선 4500H.P.의 Z. peller 2척을 이용하여 안전 접안 조선하는데 큰 위험이 없음을 알았다. 그러나 돌풍율 25%를 포함한 강풍 16.9m/sec 이상의 기상상태에서는 선박조종이 위험하게 됨을 알았고, 돌풍율을 포함하여 풍속이 16.9m/sec 에 달하는 강풍 하에서 대형 컨테이너 선박을 부득이 접안 조종할 때는 4500 H.P. Z. peller 3 척으로 조선보조를 받아야 함을 알았다.

• 한국해양공학회지
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• 제32권1호
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• pp.51-61
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• 2018

In this study, the operability of an FLBT (floating LNG bunkering terminal) was evaluated experimentally. Model tests were conducted in the KRISO (Korea Research Institute of Ships and Ocean Engineering) ocean engineering basin. An FLBT, an LNG carrier, and two LNG bunkering shuttles were moored side by side with mooring ropes and fenders. Two white-noise wave cases, one irregular wave case, and various regular wave cases were generated. The relative local motions between each LNG loading arm and its corresponding manifold in the initial design configuration were calculated from measured 6-DOF motions at the center of gravity of each of the four vessels. Furthermore, the locations of the LNG loading arms and manifolds were varied to minimize the relative local motions.