• Journal of Ocean Engineering and Technology
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• v.32 no.1
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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.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.846-852
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• 2013

In this paper, the authors propose a new approach to control problem of the marine vessels which are moored or controlled by actuators. The vessel control problem in the specified area is called a DPS (Dynamic Positioning System). The main objective of this paper is to obtain more useful control design method for DPS. In this problem, a complicate fact is control allocation which is a numerical method for distributing the control signal to the controlled system. For this, many results have been given and verified by other researchers using two individual processes. It means that the controller design and control allocation design process are carried out individually. In this paper, the authors give more sophisticated design solution on this issue. In which the controller design and control allocation problem are unified by a robust controller design problem. In other word, the stability of the closed-loop system, control performance and allocation problem are unified by an LMI (Linear Matrix Inequality) constraint based on $H_2/H_{\infty}$ mixed design framework. The usefulness of proposed approach is verified by simulation with a supply vessel model and found works well.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.93-101
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• 1993

This paper deals tilth an efficient algorithm in spectral fatigue analysis of ship structures. The concept of stress influence coefficients is suggested in order to obtain stress transfer functions efficiently which are the structural responses for unit load components. Strip method is applied to obtain the motion response and pressure distributions exerted on the hull. Since a number of the structural analysis should be performed for the various wave frequencies and heading angles in the spectral analysis, the algorithm developed in this study improves the efficiency of the analysis. Finally, the calculation example with application to this concept is shown in this paper.

• Journal of Ocean Engineering and Technology
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• v.29 no.4
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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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.2
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• pp.147-154
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• 2012

In head sea, a ship has mainly the longitudinal motion such as vertical acceleration and pitch. In that case, the motion characteristics of a ship will have changed as the location different from each of place vertically and horizontally on board. The author carried out an experiment about the ship's vertical acceleration and pitch according to the location for the head sea, and analyzed the data with the aid of the statistical and spectral analyzing method to get the motion characteristics of the vessels. The response of vertical acceleration and pitch not deeply depend on the decks vertically, but displayed the relative big different value horizontally even if same deck. The biggest response of vertical acceleration and pitch among the accommodations was shown at scientist room, but the value of it not reached to the minimum requirement of ISO 2631-1 for working on board.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.38-43
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• 2005

The present study is concerned with the numerical analysis of the sloshing impact pressure of the Liquefied Natural Gas (LNG) carriers in rough sea. The reliable predictions of the both random tank motions in irregular waves and violent fluid flow in the LNG tanks are required for practical sloshing analysis procedure of LNG carriers. The three-dimensional numerical model adopting SOLA-VOF scheme is used to predict violent free surface movements of LNG tank in irregular motions. For accurate input motion of tank, a three-dimensional panel method program called SSMP (Samsung Ship Motion Program) is applied for seakeeping analysis. Comparison studies of sloshing analysis are carried out for No.2 tank of 138K and 205K LNG carriers to verify the safety of the LNG containment system of the proposed 205K large LNG carrier.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.54-64
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• 1996

It seems that blowing air bubble out of the bulb surface of a ship of flat bottom will reduce the frictional resistance, since wetted area of the hull surface is reduced owing to air bubble staying close to the surface. To as certain this concept, at first, the limiting streamlines around the bow was observed, and local distribution of pressure and shear stress, due to the change of air-blowing position, air supply pressure, and the model speed, was investigated. It was found that the local friction was reduced near the bulb and air-bubble formations also play an important role as a drag component. This paper can be considered as a preliminary study on the drag reduction of conventional ships by the micro-bubble injection.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.17-23
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• 1990

When a thin walled member is subjected to compression in a condition such as collision, the energy is mainly absorbed by axial crumpling. In this case, dynamic crushing strength of the member is increased due to the effects of strain-rate compared with the static strength, even though the inertia effect is neglected. In this paper, the method of predicting the static crushing for tubular members is presented using the kinematic method of plasticity. Since, a predicted crushing load, taking account of the dynamic yield stress, usually overestimates the effects of strain-rate, the average plastic flow stress for the effects of strain-rate is used to obtain the dynamic crushing load for tubular members. The analytical results are compared with the experiments published in references, and a good correlation is observed.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.46-51
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• 2006

Moonpool characteristics of a cleaning skip related with the performance of a skip are experimentally investigated. Resistance performances of the ship and flow patterns in the moonpool are observed, in order to determine the effect of different shaped moonpool. The ways to reduce ship pithing motion caused by force in the moonpool are examined. Experimental results, using a scale model of cleaning ship with moonpool, show that the step arranged in tier under water leads to significant improvements in performance, such us resistance and ship pithing motion. Depending upon the shape of step in the moonpool, the results indicate that the increment of resistance performance may be up to 35%, especially in the case of no step or high step.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.498-505
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• 2008

Many researches have been studied on in-cylinder flow as one of dominant effects for an engine combustion. The combustion phenomena of reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. To know this relationship definitely, this paper describes analytical results of the tumble motion, swirl motion, turbulence intensity, turbulence inside the cylinder of marine engine. 3-D computation has been performed by using STAR-CD solver and es-ice.