• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.4
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• pp.363-371
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• 1996

The Steering and Sailing Rules of International Regulations for Preventing Collisions at Sea now in use direct the best aid - action to avoid collision by the stand - on vessel. But these rules do not refer to the safety relative distance between two vessels when she should take such action. In this paper, the author analyzed the ship's collision avoiding actions from the viewpoint of ship motions and worked out mathematical formulas to calculate the relative distances necessary for taking action to avoid collision. Figuring out the values of maneuvering indices through experiments of 11 actual ships of small, medium, large and mammoth size, the author applied these values to the calculating formulas and calculated the minimum relative distances. The main results are as follows: 1. It was confIrmed that the stand - on vessel should keep the greatest relative distance for taking best aid - action to avoid collision when the cross angle of course was $90^{\circ}$ and near it(70-$90^{\circ}$ ). 2. When the cross angle of course was $90^{\circ}$ , the minimum relative distance of small vessel(GT: 160-650tons) was found to be more than about 6.8 times of her own length, and those of medium(GT : 2,300-3,500tons), large(GT : 22,OOO-62,OOOtons) and mammoth(GT : 91,000-139,000tons) vessels were found to be more than about 9.0 times, about 5.4 times and about 6.8 times of their own lengths. 3. It was confIrmed that collision danger was greater when crossing angle was obtuse than in an acute angle, therefore greater relative distance was to be kept by the stand - on vessel for taking best aid - action to avoid collision in the case of the obtuse angle. 4. In every vessels, in the case of $90^{\circ}$ cross angle of course the safety minimum relative distance was found to be more than about 9.0 times of their own lengths.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.2
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• pp.171-178
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• 2015

This research is the first research on developing the speed limit select model and also it is the result of the research on the importance of each element and consideration factors when selecting the speed limit. For the consideration factor discrimination and calculation of the importance, the delphi method and AHP method was used. The delphi survey was processed through third round survey, 5 high consideration factor(Level 1) and 23 low consideration factor(Level 2) was discriminated. During the process of the third delphi survey, when the CVR cost was in the range between 0.4~1.0 it was treated as the consideration factor when selecting the speed limit and less than 0.4 cost was eliminated. In the process of the second delphi survey, 33 consideration factors were discriminated but was reordered into 23 categories through the third survey. Based on the 23 categories earned through the third delphi analysis, the AHP survey was processed. The result of the AHP survey was that out of the importance of the 5 high consideration factor(Level 1), the traffic condition was evaluated as the number one factor and the vessel condition, waterway condition, environment condition, supporting condition and etc. conditions were evaluated following the traffic condition. Out of the 23 low consideration factor(Level 2) consideration, the visibility was evaluated to be the first important and the performance of the vessel steering, objective factors within the harbor, amount of traffic and density, distance between the passing vessel, speed of the steering capacity and tidal current were the following evaluated factors.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.613-619
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• 2017

Recently, the size of container ships has been progressively increasing, and much attention is required for safe navigation in shallow areas such as coastal waters and ports due to increases in draft. It is necessary to understand the characteristics of ship motion not only in still waters but also with waves. Especially in shallow regions, squat due to the vertical movement of the ship can be an important evaluation factor for the safe navigation, and wave drift force acting in the horizontal direction can have a great influence on the maneuverability of a ship. In this study, a numerical simulation using computational fluid dynamics has been performed for the wave exciting force acting in the vertical direction and the wave drift force acting in the horizontal direction for a very large container vessel sailing in shallow zone. As a result, it was found that total resistance in still waters greatly increased in shallow water. Wave drift force was shown to decrease given longer wavelengths regardless of water depth. It was observed that the wave exciting force in shallow water was considerably larger than at other water depths. As wave height against the central part of the ship lowered, the aft side rose.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.71-74
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• 2006

Currently offshore fisheries are one of shrinking industries and fishermen are getting older. Moreover it is difficult to work fisheries for decreasing fishermen as the time goes. Two people per a boat work together at least for proper fisheries. If the unskilled fisherman boards on boat, it will make some troubles to speak each other and diminish the efficiency of working because one person should control the boat. So it need to study the remote control system for leasure and outboard engine that can control and work at the same time. The remote control system is consisted of engine revolution, steering gear and forward reverse neutral gear controls. These three controls are made by position and speed control using DC motor, and microprocessor is used to communicate and control the engine speed This system can be controled and worked alone and we tested the system at sea and confirmed that the system works properly.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.383-384
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• 2010

The control surface on a ship is to control the motion of it in forward and backward states. In this paper, the measured results has been compared with each other to predict the backward flow characteristics of the single rudder's 2-dimensional section at $Re=2.0\times10^4$ using 2-frame grey level cross correlation PIV method especially, The separation region appears at 10 to 20 degrees angle of attack in a forward state. The separation point and boundary layer demonstrate in the same angle of attack compared it with the forward states.

• Journal of Korean Port Research
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• v.13 no.1
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• pp.133-146
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• 1999

Mokpo coastal area is connected to the adjacent a long river and two large basins. It is essential for port planning coastal zone management and environmental impact study to analyze the data related to the ship operation and variation of current and water quality due to the development of water area including dredging reclamation and estuary barrage. The Yongsan river estuary weir and Yongam-Kumho basins discharge much of water through water gates for the purpose of flood control and prohibit salt intrusion at the inland fresh water area. To meet this purpose discharge through the gates have been done at the period of maximum water level difference between inner river and sea level. This discharged water may cause the changes of current pattern and other environmental influences in the vicinity and inner area of semi-closed Mokpo harbor. In this study ADI method is applied to the governing equation for the analysis of the changes on current pattern due to discharged water. As the results of this study it is known that the discharging operation causes many changes including the increase of current velocity at the front water area at piers approaching passage and anchorages. Discussion made on the point of problems such as restricted maneuverability and the safety of morred vessels at pier and anchorage. To minimize this influence the linked gate operation discharging warning system and laternative mooring system are recommended.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.387-388
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• 2010

An open water rudder test was carried out to figure out the flow characteristics around a twin rudder at $Re=1.5\times10^4$. In the analysis, the unique characteristics of a twin rudder, which effects rudder farces, were explained. The analysis is included varying angles of attack fram 10 to 30 degree. In this paper, the measured results has been compared with each other to predict the performance characteristics of a twin rudder's 2-dimensional section by 2-frame grey level cross correlation PIV method. The side force of the rudder could be mainly improved at 0.75L.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.3-12
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• 1984

Up to now, it has been common to treat the maneuvering motion of a ship as a 3-degree-freedom motion i.e. surge, sway and yaw on the sea surface, for the simplicity and mathematical calculation, and it is quite acceptable in the practical point of view. Meanwhile, considering the maneuverability of a ship under the special conditions such as in irregular waves, in wind or at high speed with small GM value, it is required that roll effect must be considered in the equation of ship motion. In this paper the author tried to build up the 4-degree-freedom motion equation by adding roll. And then, applying the M.M.G.'s mathematical model and with captive model test results the roll-coupled hydrodynamic derivatives were found. With these the author could make some simulating program for turning and zig-zag steering. Through the computer simulations, the effect of roll to the ship maneuver became clear. The effect of the wind force to the maneuverability was also found. Followings are such items that was found. 1) When roll is coupled in the maneuvering motion, the directional stability becomes worse and the turning diameter becomes smaller as roll becomes smaller as roll becomes larger. 2) When maneuver a ship in the wind, the roll becomes severe and the directional stability becomes worse. 3) When a ship turns to the starboard side, the wind blowing from 90 degree direction to starboard causes the largest roll and the largest turning diameter, and the wind from other direction doesn't change the turning diameter. 4) When a ship is travelling with a constant speed with rudder amidship, if steady wind blows from one direction, the ship turns toward that wind. This phenomenon is observed in the actual seaways.

• Journal of Navigation and Port Research
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• v.34 no.5
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• pp.325-330
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• 2010

An open water rudder test was carried out to figure out the flow characteristics around a twin rudder at $Re=1.5{\times}10^4$. In the analysis, the unique characteristics of a twin rudder, which affects rudder forces, were explained. The analysis includes varying angles of attack from 10 to 30 degrees. In this paper, the measured results have been compared with each other to predict the performance characteristics of a twin rudder's 2-dimensional section by 2-frame grey level cross correlation PIV method. The length L=0.75C between upper and lower rudders could be defined as the critical length.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.66-72
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• 1994

For the reliable prediction of maneuverability of a ship, lots of captive model tests have been carried out for over 10 years. But the parameters appearing in the mathematical model are so versatile and showing complex characteristics, and it is still hard to establish the useful formulae that we can adopt directly in the design stage. In this paper, the most important parameters in the mathematical model. i.e.($1-\omega_P$) the effective wake fraction at propeller, and $\delta_R(\beta_R)$), the effective rudder inflow angles are investigated by the captive model tests at the circulating water channel. The model is tested at designed speed and at low speed, and the drafts at both full load and ballast load conditions are taken. Propeller thrusts and rudder normal forces are measured at the given drift angle and propeller revolution. These forces are used for the analysis of the effective flow velocity or flow direction, to the propeller or rudder.