• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.52-58
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• 2013

Operation Abstract : Operational cost required for navigating a ship may differ from according to type, scale, economic speed, navigation area and other factors. However, it is known that the fuel oil price ratio takes 50~60 %. It is the current trend because of the use of poor quality fuel and it is reviewed even for small to medium sized ships to save the operational costs due to the recent rise of international oil price. Furthermore, ocean carriers are taking action to low speed navigation as the alternative method of reducing fuel consumption. Hence, in this study, fuel consumption of main engine was measured by using actual operating ship data compared with sea speed at sea. It was suggested that the area of M/E's load(70 %) lower than NCR is the optimal navigating condition through the relation between speed and fuel consumption compared with advance ratio together with the load.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.11-18
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• 1998

This study describes sea trial tests for a waterjet propulsion system attached in the hybrid super high speed cargo ship named "Narae". A measuring technique of jet velocity, gross thrust and impeller torque for the waterjet system is explained. From the measured data in sea trial test, performance of the waterjet propulsion system is analyzed and compared with model test results of a similar waterjet system which was carried out in 1996. The erective horse power estimated from sea trial tests shows a good agreement with resistance test results of the model ship. The optimum rising height is estimated as 0.75 m, and the overall efficiency of the waterjet system is predicted as 0.315 at 15 knots. Useful data such as the pump performance, the jet efficiency, the losses of inlet duct and nozzle were obtained. Test results show a similar behavior to the model test results.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.50-59
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• 1997

Shipbuilder checks the status of main engine and propeller operation before sea trial. Generally these tests are carried out at a quay during fitting out of the ship. For these tests the operator has to estimate the maximum RPM with permissible torque and thrust to ensure the safety of the mooring line and ship. In this paper, the propeller characteristics according to the draft variation for a moored ship is inveatigated. From these tests, it is shown that shaft submergence is a dominant parameter in the propeller performance at shallow shaft submergence and that the propeller performance is dependent upon the propeller RPM when the shaft submergence is kept unchanged. In this study, a simple formula of the required thrust for a given propeller shaft submergence and propeller RPM is derived. 1be propeller thrust, which is calculated by another formula in case of dtep draft, is compared with results of bollard pull test for FPSO.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.135-144
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• 1994

The coupled vibration of the deck house and stern structure, which was experienced on a 12,900 TDW Ro/Ro ship, has been studied. It was a large-scale vibration problem where the structure resonates with the propeller excitation at the first blade passing frequency. After discussing the structural characteristics of the ship, the vibration characteristics measured ducting the sea-trial are presented and compared with the analysis results which are based on a 3 dimensional finite element(FE) model. The FE model is also used to verify various reinforcement options and to predict their effectiveness. A substantial reduction or the vibration was confirmed during the sea-trial after installing a few selected reinforcement. The forced vibration response, which is computed using the FE model, is compared with the measured data. The change of the vibration characteristics according to loading conditions is also studied.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.1-10
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• 2002

Hull-propeller-rudder interactions are studied by the iterative computational procedures. Hull effects on the propeller are reflected through the effective velocities computed by the vortex ring method which used the measured nominal wake as input data. A potential based panel method has been developed to solve the propeller-rudder interactions using the obtained effective velocities. Steady flow characteristics around the rudder surface can be obtained by computing the induced velocities on the rudder by the propeller and vice versa are computed by the iterative manner until the converged solutions are obtained. Flow characteristics around the propeller and the rudder are measured by Laser Doppler Velocimetry(L.D.V.) in large cavitation tunnel at Samsung Heavy industries. The gap flow model is adopted to solve the characteristics of the horn rudder. Numerical results are compared with the experimental values and the computed velocity fields and pressure distributions with rudder angle on the horn rudder surface show good agreement with measured ones in large cavitation tunnel.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.805-810
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• 2011

An experiment was carried out to figure out the instantaneous flow characteristics in the wake of the transom stern's 2-dimensional section by 2-frame grey level cross correlation PIV method at $Re=3.5{\times}103$, $Re=7.0{\times}103$. The stern angles of models were learning at $45^{\circ}$(Model "A"), $90^{\circ}$(Model "B") and $135^{\circ}$(Model "C") respectively based on the survey results of real ships. The depth of wetted surface is 40mm from free surface. As Reynolds number increases, vortices increase in volume and move their way to the downstream. Flow separation appeared at the end of model's bottom.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.497-503
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• 2018

Passenger ships and training ships have a common feature in that they serve many passengers. Thus, safe navigation is very important. During normal sailing, a ship may turn using various types of steering, including maneuvers to avoid collisions with dangerous target. When a ship turns, a heeling angle occurs. If trouble arises during sailing, a dangerous heeling angle may result or a capsizing accident. In this study, the heeling angle during turning was measured through experimentation with two training ships similar to passenger ships. These findings were compared with theoretical formulas for heeling angle when turning. We confirmed that the limit of the maximum heeling angle estimation using heeling angle formula when turning presented in IMO stability criteria. In addition, it was confirmed that the maximum estimated heeling angle can be reached by applying the result calculated in the theoretical formula 1.4 times when turning right and 1.1 times when turning left to reflect sailing speed when of rudder hard over. It is expected that this study will provide basis data for establishing safe operation standards for the prevention of dangerous heeling angles when turning.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.6
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• pp.587-593
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• 2020

The securing safety of ferry ships on the domestic coast is evaluated by comparing the external force applied and the securing device based on the cargo weight and hull acceleration that can exist at the loaded position. The hull acceleration based on the domestic standard, which is the basis for securing safety evaluation, is applied without reflecting the characteristics of the ship and the sailing conditions. In this study, a total of 12 acceleration measurements were performed at four points of the hull of a ship with a DWT 6,800 ton class 15.5 knots passing through Busan-Jeju to analyze the hull acceleration of the domestic coastal ferry ship. Data were collected for the buoy. For a theoretical comparative analysis of the limited measurement results, the response amplitude operator (RAO) was analyzed through frequency-response analysis by numerical simulation, and acceleration analysis for the four points was performed using the RAO results. Based on the acceleration comparison, differences in the degree of each position were observed, but in the case of the Y-axis acceleration, the analysis was 1.81 m/s², and the measurement was 1.47 m/s². The analyzed simulation result was as high as 0.34 m/s². Moreover, analysis was performed at 22 % level, and measurement at 18 % level.

• Journal of Navigation and Port Research
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• v.32 no.6
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• pp.439-445
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• 2008

Various turning tests were carried out according to the rudder angle, turning direction, and the speed etc. with the ship's maneuverability measuring system on the training ship HANBADA. After that they were compared with each other on the turning circle, maneuvering performance index and the distance of new course, and then found out that they were satisfied with the IMO maneuvering standards. And the turning circles of port were smaller than those of starboard with all the rudder angles and maneuvering indexes such as K and T were relatively bigger than other vessels. Also, the distance cf new course was measured to $125{\sim}300m$ in case of the new course on $30^{\circ}{\sim}90^{\circ}$. All of these results will be helpful to escape from collision and to alter course on coastal voyage.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.1-7
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• 2002

As the existing noise measuring device was affected the flow-field and structural vibration directly, new experimental device was required. Two Hydrophone Boxes are designed and their performances are investigated. The noise level of the KRISO cavitation tunnel is compared with those of the other cavitation tunnels which have been designed for the noise study. The present experimental results show the possibility of the full-scale prediction for propeller cavitation noise and the improvement of the measurement performance at the range of low-frequency.