• 수산해양기술연구
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• 제50권2호
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• pp.147-153
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• 2014

The purpose of this paper is to examine the roll damping characteristics by bilge keels on the fishing vessel. Unlike other degree of freedom motions, roll motion is highly nonlinear. However the quantitative evaluation of roll damping combined with waves is very important for the fishing vessel. To reduce roll motion, roll motion stabilizers such as a bilge keel is used due to easy made and cheap cost rather than anti-rolling tank and fin-stabilizer. Authors paid attention to the shape of bilge keel and waves to grasp the roll damping for the fishing vessel and studied about the difference of tendencies of roll angle following the shapes of bilge keel. The model ship was the offshore large purse seiner and four types of bilge keel were used. The data from the experiments were provided and analyzed to investigate the rolling characteristics of the model ship being affected by the wave height, wave period and bilge keel shape. The results of the study showed that three types of the bilge keel have little effective, but only one has an effect on the roll damping. So bilge keel shape and its attachment method need to be a future study for the practical use in fishing vessel.

• 한국해양공학회지
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• 제29권3호
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• pp.231-240
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• 2015

FPSO model tests of mooring line failure were carried out in the ocean basin at KRISO. The characteristics of the motions and mooring lines were investigated. The FPSO ship was moored using an internal turret and catenary mooring. The test model was 1/60 scale. The mooring lines were designed to satisfy the characteristics of the original mooring lines using the truncation method. The experiments were conducted under various environments: a safe wave, current and wind condition; single broken mooring line condition; and transient mode condition. The moment of the break was determined based on experimental test results. The results showed that the FPSO behavior and mooring line tensions were acceptable under the failure condition.

• 대한조선학회논문집
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• 제56권6호
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• pp.550-558
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• 2019

The roll motion of a general vessel, which is more influenced by resonance as compared to other motions, adversely affects the passenger and hull. Therefore, reducing the roll motion through an anti-rolling system is critical, and most ships use various devices such as anti-rolling tanks, bilge keels, and fin stabilizers to accomplish this. In this study, a simplified model is developed for the application of an anti-rolling device for unmanned semi-submersible vessels. The applied anti-rolling device is installed on the stern and stem of a ship using a pair of servo motors with added weight, and the motor is controlled through the Arduino. The moment of the motor is designed and implemented based on a mathematical model such that it is calculated through the restoring force according to the heel angle of the ship. The performance of the proposed system was verified by utilizing the roll damping coefficient calculated by the free-roll decay test and logarithmic decrement method and was validated by a towing tank test. The system is expected to be used for unmanned vessels to perform sustainable missions.

• 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.

• 대한조선학회논문집
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• 제49권1호
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• pp.6-13
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• 2012

As ocean resources in shallow water areas are being exhausted, deep sea development is becoming common these days. Therefore floating type offshore structures are more competitive than fixed type structures, and FPSO is the most popular one these days. FPSO's are generally operated in a specific region and positioned to meet mostly head or bow waves in order to reduce roll motions. However this makes these vessels more vulnerable to green water around the bow region, and therefore the bow shape must be properly designed to mitigate green water damage. In the present study, experimental results for three different FPSO bow shapes in regular head waves were analyzed and compared to each other. Also CFD computations were carried out as a sample validation case for the database built for CFD code validation.

• 대한조선학회논문집
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• 제47권3호
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• pp.421-429
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• 2010

In this paper, in order to analyze the dynamic response of a floating crane when it lifts a heavy cargo, the boom of the floating crane is considered as an elastic beam. The boom is divided into elements based on finite element formulation and the floating frame of reference formulation and nodal coordinates are employed to model the boom as a flexible body. As an extension of the previous study, in order to consider spatial motion in waves, the coupled equations of motions of the 6 degree of freedom (DOF) floating crane and 6 DOF cargo are developed based on the flexible multibody system dynamics. The 3 dimensional deformation of the elastic boom is considered with 18 DOF. The dynamic simulation of the floating crane and the cargo is performed under regular wave conditions with various cargo weights. Finally, the effects of the elastic boom on lifting cargo are discussed by comparing the simulation results between the elastic boom and a rigid boom.

• 대한조선학회논문집
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• 제38권2호
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• pp.33-43
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• 2001

드릴쉽과 셔틀탱커등 특수선의 건조가 활발해지면서 정해진 위치에서 장시간 작업해야 할 목적으로 동적 자기위치 유지시스템(Dynamic Positioning System)을 장착하는 선박이 늘어나고 있다. 본 논문에서는 DP 시스템의 구성 요소를 소개하고, 수조에서 실험한 결과를 바탕으로 제어이론과 필터이론에 따른 DP성능을 비교하였다. 실험에 사용한 선박은 10만톤급 드릴쉽으로 모델의 길이가 4m이며, 방향이 고정된 3개의 추진기를 사용하였다. 실험 내용은 명령에 따라 주어진 궤적을 이동하는 능력과 파도가 있는 외란조건에서 원하는 선수각을 유지할 수 있는지를 살펴보았다. 추진력을 구하기 위하여 PID 이론을 적용하였고, 제어게인의 변화에 따른 제어특성을 살펴보았다. 선형운동성분과 계측잡음을 제거하기 위하여 칼만 필터와 디지털 필터를 적용하였고, 각각의 필터성능을 비교 검토하였다.

• 한국해양공학회지
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• 제31권6호
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• pp.379-387
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• 2017

In this study, a pile-guide mooring system (PGMS) was designed for an offshore liquefied natural gas bunkering terminal (LNG-BT), which is an essential infrastructure for large LNG-fuelled ships. The PGMS consisted of guide piles to restrict five motions of the floater, except for heave, as well as a seabed truss structure to support the guide piles and foundation piles to fix the system to the seabed. Singapore port was considered for a case study because it is a highly probable ports for LNG bunkering projects. The wave height, current speed, and wind speed in Singapore port were investigated to calculate the environmental loads acting on the hull and PGMS. A load and resistance factor approach was used for the structural design, and a finite element analysis was performed for design verification. The steel usage of the PGMS was analyzed and compared with the material usage of a gravity-based structure under similar LNG capacity and water depth criteria. This paper also describes the water depth limit and wave conditions of the PGMS based on estimation of the initial investment and the present value profit difference. It suggests a suitable LNG-BT support system for various design conditions.

• Journal of Advanced Marine Engineering and Technology
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• 제36권8호
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• pp.1010-1015
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• 2012

DME는 천연가스로부터 합성할 수 있는 대량의 에너지원이 된다. 한국가스공사는 DME 상업규모의 생산플랜트를 개발하고 이의 국내 공급을 위해 해외 자원 확보를 추진하고 있다. 본 논문은 응력과 변형 해석을 통하여 DME저장탱크의 설계기준을 제공하였고, DME FPSO저장탱크의 증발현상을 파악하기 위하의 증발을 발생시키는 원인인 열유입과 선박의 유동에 따른 증발량 실험을 수행하였다. 실험결과, 롤링의 각도가 커지고 액체 충전량이 많을수록 증발량이 증가하였다. 롤링각도가 15도 일 때의 증발량은 정지상태의 열유입 만에 의한 증발량 보다 약 20%가 증가하였다.

• 수산해양기술연구
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• 제56권1호
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• pp.61-70
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• 2020

In this study, system modeling and dynamic analysis of crane are conducted. Especially, among many different kinds of a crane system, the issues on crane operating problems installed on the vessel are considered. As well known, marine systems including cranes are exposed to various disturbances such as vessel motions, hydrodynamic forces, wave and wind attack, etc. In order to analysis the system dynamic with environmental conditions, the authors derived the nonlinear dynamic model of offshore crane and derived a linear model which is used for designing the control system. Using the obtained nonlinear and linear models, simulations were conducted to evaluate the usefulness of the obtained models. By simulation and result evaluation, the usefulness of the linear model, which presents the dynamics, is effectively verified.