• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.956-964
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• 2017

This study contributes to deepening understand of the characteristics of fishing vessel rolling motions to improve the development of capsizing alarm systems. A time domain rolling motion simulation was performed. In order to verify capsizing alarm systems, it is necessary to carry out experiments assuming a capsizing situation and perform actual fishing vessel measurements, but these tasks are impossible due to the danger of such a situation. However, in many capsizing accidents, a close connection with rolling motion was found. Accordingly, the rolling motion of a fishing boat, which is the core of a fishing vessel capsizing alarm system, has been accurately measured and a time domain based on a rolling motion simulation has been performed. This information was used to verify the algorithm for a capsizing alarm system. Firstly, the characteristics of rolling motion were measured through a motion experiment. For small vessels such as fishing vessels, it was difficult to interpret viscosity due to analytical methods including CFD and potential codes. Therefore, an experiment was carried out focusing on rolling motion and a rolling mode RAO was derived.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.226-233
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• 2002

In the field of research of sea keeping quality, much development has been made in recent years using the method of calculation based on the strip theory. It is very important to investigate the hull response of a fishing vessel in waves to ensure the safe navigation and fishing operation in rough seas by preserving excellent sea keeping qualities. For this purpose, the author measured various responses of three fishing vessels in waves using real sea experimental measuring system and analyzed the experimental data The results obtained can be summarized as follow. 1. The amplitudes of pitching motion in the experiments appeared low values with more than one peak occasionally in following sea and quartering sea, and the band width of those was found to be wide relatively. 2. The amplitudes of rolling motion in the experiments appeared high values with only one peak in following sea and quartering sea regardless of ship's tonnage, and the band width of those was found to be narrow relatively. 3. The comparisions of theoretical results with those of experiments for the pitching motions and rolling motion in following sea and quartering sea show that the theoretical values are higher slightly than those of experiments in both directions and the period at which the peak appears in the calculations and the experiments has good agreement approximately 4. The calculated responses of two vessels under a assumed wave of 2.2m height and 5.0sec period showed that the response of pitching motion of ship-A are 2.2 times bigger than those of ship-C in following sea and quartering sea, and the response of rolling motion of ship-A is 4.2 times bigger than that of ship-C in quartering sea.

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.39-45
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• 2004

We have investigated the usefulness of an active stabilizing system to reduce ship rolling under disturbances, using varying reaction of the flaps. In the proposed anti-rolling system for a ship, the flaps, as the actuator, are installed on the stern, in order to reject the rolling motion induced by disturbances, such as waves. The action induced by the flaps, which is dependent upon the power of the disturbances, can keep the ship in balance. In this study, we define the system parameters under the given system structure, using spectral analysis and experimental studies. Based on this information, we design the controller to evaluate the usefulness of the proposed system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1742-1743
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• 2011

항해 중인 선박에 가장 영향을 미치는 것은 해양파이다. 해양파는 주로 바람에 의해서 생성이 되며 지역적으로 바람의 세기와 방향이 다르기 때문에 파의 높이와 파의 길이가 정해져 있지 않은 불규칙파가 발생한다. 선박에 미치는 해양파의 힘에 따라 횡동요의 크기 및 주기가 달라진다. 해양파의 힘의 크기가 선박의 복원력보다 크게 되면 선박은 전복이 된다. 이런 이유로 선박 운동을 인위적으로 억제하기 위하여 Fin Stabilizer를 사용하게 되었다. Fin Stabilizer는 짧은 시간에 동작하여 선박의 안전을 향상시킬 수 있으며, 운행 효율을 높일 수 있기 때문에 최근 들어 널리 사용되고 있는 방법이다. 본 논문에서는 해양파의 힘이 선박에 영향을 미칠 때의 횡요각 변화를 관찰하고 설계한 제어기의 성능정도를 위한 Simulation을 수행하였다. Simulation 결과를 토대로 Fin Stabilizer를 제어하기 위한 Digital 제어기를 구성하였다.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.4
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• pp.39-45
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• 1980

내항성이 우수한 선형을 개발하기 위해서는 초기설계단계에서 이미 그 배의 해상에서의 거동을 예측할 수 있어야만 한다. 이 보고서에서는 임의의 입사각을 갖는 규칙파중을 항주하는 선박이 겪게 되는 동요중에서 횡동요, 수평동요 그리고 선수동요의 연성운동방정식의 해를 Tassi-Takaki가 수정한 스트립이론을 적용하여 해석하였다. 제15차 ITTC의 내항성 위원회의 보고서에서 발표된 콘테이너선형에 대한 결과와 똑같이 선형에 대해 본 프로그램을 사용하여 계산한 수평동요, 횡동요 그리고 선수동요의 운동응답을 비교하여 보았으며, 상당히 만족스러운 결과를 얻었다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1031-1037
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• 2021

The frequency of marine accidents of vessels in Korea is steadily increasing and it is concentrated on small vessels with less than 10 tons of gross tonnage. Therefore, preventing capsizing accidents in small vessels is important to reduce the cost in terms of human and property damage due to such accidents. However, research on the seakeeping performance of small vessels has been insufficient, and there are no domestic and international regulations on seakeeping performance. Therefore, in this study, capsizing accidents caused by poor loading conditions were investigated by examining the adjudications of the small vessels in which the capsizing accidents occurred. Hydrostatic calculations and seakeeping performance analysis were performed for a representative vessel. A vessel generally performs a six-degree-of-freedom motion during operation. In this study, the response amplitude operator and response spectrum of a representative vessel were calculated to determine the roll motion. Moreover, a short-term statistical analysis of the vessel according to the loading conditions was performed for the wave stationary status for 3 h. From the results, it was estimated that, when the loading condition of a small vessel is poor, its roll motion increases, greatly reducing its stability.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.33-39
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• 2004

A ship runs with various modes of motion due to waves. Among the modes, roll mainly influences on the safety of cargos and crew's fatigue. Therefore a ship equipped with anti-rolling devices are on an increasing trend. In this research, we developed a free running model ship to evaluate the performances of fin stabilizer and moving weight stabilizer. Also those performance tests were carried out through the proposed test procedure.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.813-818
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• 2007

There are the C.W.C and Towing Tank to the model-test equipments of the boat. A model testing of the high speed boat have a difficult in the performance verification because of very a small the scale-ratio of the ship-model and restricted by flow-velocity of the C.W.C and X-carriage velocity of the T.T. In general, the stepped hull boat is a high of fuel-efficiency because of the resistance reduction by a small wetted surface-area in correspond without stepped-hull boat. But It have a tendency to be bad the rolling performance by reduced stern wetted-area In this paper, the high speed stepped planning-boats with & without attached a stern body were performed to compare the effect of resistance and rolling performance by using sea model-test method.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.38-47
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• 1992

The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Within the framework of potential theory, matched asymptotic expansion techniques are exployed to analyze the problem. The fluid domain is divided into the ocean and the harbor regions for the analysis of wave response in a harbor without ship. The wave responses in both the ocean and the harbor sides are solved first independently in terms of Green's functions, which are the solutions of the Helmholtz equation satisfying appropriate boundary conditions. Slender body approximations are used to obtain the velocity jumps across the ship, which are associated with the symmetric motion modes of the ship. Unknowns contained in each solution are finally determined by matching at an intermediate zone between two neighboring regions. Theoretical results predict the ship motion qualitatively well. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.

• Journal of Ocean Engineering and Technology
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• v.33 no.4
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• pp.322-329
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• 2019

The magnitude of the roll motion of a floating structure depends on the roll damping acting on the body. In other words, the roll damping of a floating structure must be accurately obtained in order to precisely evaluate the roll motion. Various methods are used to evaluate the roll damping of a floating structure, such as the linear potential theory, computational fluid dynamics (CFD), and model tests. However, it is difficult to evaluate the roll motion of a floating structure with appendages such as a bilge keel and riser slot due to the limitation of ignoring the viscous effects in the linear potential theory. Among these methods, a model test based on a free decay test and harmonic excited roll motion (HERM) is known to be the most reliable method to estimate the roll damping of the floating structures. In this study, model tests using free decay and HERM techniques were performed in the Ocean Engineering Basin (OEB) of KRISO with various types of midship sections. The roll damping results were estimated based on post-processing methods using both techniques, and the roll damping results were compared.