• Journal of the Society of Naval Architects of Korea
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• v.56 no.3
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• pp.273-280
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• 2019

Predicting ship manoeuvrability is attracting widespread interest in the field of analyzing maritime accident to simulate a highly accurate track of a ship in abnormal accident situations. This study investigated the manoeuvrability of a ship in abnormally heeled condition. Free Running Model Tests (FRMT) with 1/65.83 scaled KCS (KRISO container ship) were conducted in three heeled conditions; $35^{\circ}$ turning circle tests and 20/20 zigzag manoeuvring tests were conducted in $0^{\circ}$, $-10^{\circ}$, and $-20^{\circ}$ conditions. The test results showed that the heeled to port condition significantly affected starboard turning and zigzag characteristics; the tactical diameters in the turning circle tests decreased, and the first overshoot angles in the zigzag tests increased when the ship was in the larger heeled condition. These results indicate that the roll angle of the ship considerably affects yaw rate and speed decrease of the ship. The turning and zigzag indices from trajectory and navigation data in the study were provided for benchmark data sets.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.185-188
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• 2019

In this paper, the towing stability of the LNG bunker barge is estimated. Currently, LNG bunkering barge is being developed as an infrastructure for the bunkering of LNG (Liquefied Natural Gas), an eco-friendly energy source. Since the LNG bunker barge are in the form of towed ship connected to the tow line, the towing stability of the LNG bunker barge is very important for the safety of not only the LNG bunker barge but also the surrounding sailing vessels. The numerical code for towing simulation was developed to estimate the towing stability of the LNG bunker barge at the initial design stage. The MMG(Manoeuvring Mathematical Group) model was applied to the equations of motion and the empirical formula was applied to the maneuvering coefficients so that they could be used in the initial design stage. To validity of the developed numerical code, it was compared with published calculation and model test results. Towing simulations were carried out according to with and without stern skeg of the LNG bunker barge using the developed numerical code. Through the results of the simulations, the appropriateness of the stern skeg area designed was confirmed.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.350-360
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• 2018

Analysis of ship's manoeuverability in shallow water is an important task from the perspective of the vessels' navigational safety. Since the number of ships operated in restricted water has increased due to the enlargement of vessels and ships represent different characteristics of the manoeuverability when operated in shallow and deep water, it is significant to evaluate ship manoeuverability at initial design stage. At the initial stage of design, the estimation of manoeuverability is generally performed with hydrodynamic coefficients estimated based on empirical formula. However, the accuracy of estimating hydrodynamic coefficients by the empirical formula in shallow water is poor compared to that in deep water. Therefore, the error in the estimation of manoeuverability increases in shallow water. In this study, CFD is proposed to improve the accuracy of manoeuverability in shallow water at the initial design stage and hydrodynamic coefficients were obtained based on PMM test in shallow water. Furthermore, the ship manoeuverability was estimated both the proposed strategy and the empirical formula. At last, validity of the proposed strategy using CFD for the estimation of manoeuverability was confirmed by comparison with the manoeuverability estimation results from model test.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.4
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• pp.214-224
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• 2022

It is necessary to estimate manoeuvring characteristics of submerged bodies at the design stage in order to ensure the safe operations. In this study, added mass coefficients in the mathematical model of submerged bodies are estimated by captive model tests and numerical calculations. Two kinds of models, MARIN 'BB2'submarine model and AUV (Autonomous unmanned vehicle) model are utilized in the forced oscillation tests. Compared to BB2 submarine, AUV with cylindrical type hull form shows relatively small added masses in roll, pitch, and yaw directions. Next, numerical calculations based on potential theory are performed under the assumption that viscous effects on inertia forces are negligible. Added masses obtained by numerical calculations are in good agreements with forced oscillation test results. And if slow manoeuvres of submerged bodies are presumed, some of velocity coupled terms can be approximated by combinations of added mass coefficients.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.5
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• pp.262-270
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• 2022

The emergence of new concept ships, such as autonomous ships, has drawn much attention on the manoeuvrability of ships because of the safe navigation and operation of ships. Although the manoeuvrability of KRISO Container Ship(KCS) has been frequently reported, there have been few documents of representative manoeuvre cases conducted in various methods by one institute. This paper presents the manoeuvrability of the ship in 1/42.0 model scale by 3 methods: free running model tests, horizontal planar motion mechanism tests, and computational fluid dynamics analysis. KRISO reports KCS manoeuvre data: 35° turning circle tests and 20/20(10/10) zigzag manoeuvring tests. In addition, a simple formula for integrating and comparing manoeuvre indices, Manoeuvrability Comparing Simple Index(MCSI), is proposed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.200-207
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• 2017

The purpose in having a control surface on ships is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portions. A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the manoeuvring characteristics of the ship. In this paper, two-dimensional flow characteristics of a flapped rudder and a water-blowing control rudder were accomplished respectively by PIV method in a circulating water channel. Model test has been carried out with different angles of attack of main foil (NACA 0012) and flap's deflection angles to predict the performance of the flapped rudder and the water-blowing control rudder. The 2-frame particle tracking method has been used to obtain the velocity distribution in the flow field. $Re{\fallingdotseq}3.0{\times}10^4$ has been used during the whole experiments and measured results have been compared with each other.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.433-439
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• 2018

An investigation was conducted to determine whether the changes in the maneuvering forces and moments acting on a hull could be affected by changing the vertical center of gravity (VCG) of a tanker. The changes in the hydrodynamic forces and moment acting on a hull according to the restraint conditions of motion were examined using CFD for cases where the VCG was located at the design draught (100% of draught), under the design draught (75% of draught), and at half of the design draught (50% of draught). The following motion restraint conditions were selected: (1) fixed restraints for everything; (2) heave, pitch, and roll free restraint; and (3) heave and pitch free restraints. It was found that restraint condition (2) had the best agreement with the model experiment results. In addition, it was found that the hydrodynamic forces and moment acting on the hull with restraint condition (2) could be greatly affected in the model tests and CFD calculations by the various configurations for the vertical center of gravity of the hull. Finally, it was concluded that the location of the vertical center of gravity of the hull could be an important factor when more accurate hydrodynamic maneuvering forces and moment are estimated.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.27-37
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• 1997

The paper deals with the effectiveness of various special rudders on course stability of a ship. We adopted five types of rudder, such as one normal rudder and four special rudders, which contain two rudders with concave and convex strips on sides respectively, one flapped rudder, and one rudder with end plates on tips. In the circulating water channel, model test was carried out for measuring lift characteristics of the rudders in open water. And various captive model tests were also carried out for measuring the experimental constants related with helm angle and steering in hull-propeller-rudder system. From the test results, the changes in manoeuvring hydrodynamic derivatives due to adoption of normal and special rudders were predicted. Then course stability performances of a ship with normal and special rudders were evaluated and discussed. As a result, it is clarified that the rudder with concave or convex strips and flapped rudder have no effect on course stability, while the rudder with end plates improves course stability with effect. The result in this study is expected to be used usefully when the course stability is in issue and has to be improved without amendment of hull design at initial design phase or after construction of a ship.