• Journal of the Society of Naval Architects of Korea
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• v.51 no.5
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• pp.396-408
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• 2014

In this study, uncertainty analysis based on ITTC(International Towing Tank Conference) Recommended Procedures is carried out in the towing-tank experiment for motion responses and added resistance. The experiment was conducted for KVLCC2 model in head sea condition. The heave, pitch and added resistance were measured in different wave conditions, and the measurement was repeated up to maximum 15 times in each wave condition in order to observe the uncertainty of measured data. The uncertainty analysis was carried out by adopting the ISO-GUM(International Organization for Standardization, Guide to the Expression of Uncertainty in Measurements) method recommended by ITTC. This paper describes the details about the analysis method, uncertainty and the measured uncertainty for each source. The uncertainty analysis results are summarized as a tabular form. To validate the accuracy of the present measurement, the experimental results are compared with the results of numerical computation and other experiment. From the present uncertainty analysis, the main sources of uncertainty are identified, which can be very useful to improve the accuracy for added resistance experiment.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.103-115
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• 2018

This paper performs a numerical computation of ship maneuvering performance in waves. For this purpose, modular-type model (MMG (Mathematical Modeling Group) model) is adopted for maneuvering simulation and wave drift force is included in the equation of maneuvering motion. In order to compute wave drift force, two different seakeeping programs are used: AdFLOW based on Wave Green function method and SWAN based on Rankine panel method. When wave drift force is calculated using SWAN program, not only ship forward speed but also ship lateral speed are considered. By doing this, effects of lateral speed on wave drift force and maneuvering performance in waves are confirmed. The developed method is validated by comparing turning test results in regular waves with existing experimental data. Sensitivities of wave drift force on maneuvering performance are, also, checked.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.440-450
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• 2016

The capsizing and consequent sinking of a coastal car ferry was recently reported, with numerous human casualties. The primary cause was determined to be a sudden turn with improperly stowed and secured cargo. Part I of this study introduces how long term acceleration components are determined from seakeeping analyses. A carferry with a displacement of 1,633 tonf was selected as the target vessel. Sea data that included the significant wave heights and periods were collected at four observation buoys, some of which were far away from two main voyage routes: Incheon-Jeju and Pusan-Jeju. Frequency response analyses were performed to obtain the linearized radiation force coefficients, hydrostatic stiffnesses, and wave excitation forces. Time response analyses were sequentially performed to produce the motion-induced acceleration processes. The probabilistic distributions of the acceleration components were determined using a peak and valley counting method. Long term extreme acceleration components were proposed as a final result.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.255-255
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• 2017

본 연구에서는 고속으로 활주하는 선박의 승선감 향상 및 운항성능 특성 연구를 위해 30ton급 세관감시정의 측정위치에 따른 멀미도 해석을 수행하였다. 특히, 관공선내의 선원들은 유사시에 신속 정확한 판단이 요구되므로 측정위치에 따른 멀미도의 영향에 대한 연구가 필요할 것으로 판단하였다. 멀미도 평가는 ISO 2631-3(1985)을 기준으로 하였다. 평가 기준은 30분, 2시간, 8시간 이후 성인 100명 중 10명이 멀미를 한다는 국제표준 지표이며 조우주파수와 수직가속도 성분으로 나타난다. 멀미도 해석은 Maxsurf Motion 모듈을 이용하였다. 30ton급 세관감시정은 고속활주형 선박의 특성을 갖기 때문에 선속에 따른 트림변화를 고려하였다. 입사각은 선체 전 방향에서의 영향을 고려한 범위로 선정하였다. 선속의 경우 선박 운용상태(정박, 저속, 고속)을 고려하여 적용하였다. 측정위치의 경우 선원들의 주 활동 구역을 고려하여 선정하였다. 해석결과 멀미도의 영향은 30knot, $180^{\circ}$의 경우에 가장 크게 분석되었다.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.4
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• pp.349-359
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• 2007

In this study the hull form design with minimum resistance of domestic coastal fishing boat using a computer design procedure is carried out. The target boat is G/T 4.99 ton class fishing boat. which is one of the most popular boat in the coastal sea. For the task, the design parameters needed in preliminary stage are selected or determined from the existing boat. which has excellent resistances characteristics. In the EHP estimation during the design procedure, the main objective function is the hull resistance, and the initial hull forms before the optimization are selected from the boats that are in operation now. The EHP values from the hull after optimization process are also compared with those of the original hull to confirm its effect. Also, optimizing is investigated for the hull form to reestimate such factors as stability, laboring environment for the best design. it is expected that the results of this study here can be effectively used to improve the present design status of domestic small fishing boats.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.3
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• pp.258-268
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• 2008

The radiation potential of a ship advancing in waves is studied using the 3D time-domain forward-speed free-surface Green function and the Green integral equation. Numerical solutions are obtained by making use of the 2nd order BEM(Boundary Element Method) which make it possible to take account of the line integral along the waterline in a rigorous manner. The 6 degree of freedom motion memory functions of a hemisphere and the Wigley seakeeping model obtained by direct integration of the time-domain 3D potentials over the wetted surface are presented for various Froude numbers.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.49-58
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• 2013

Recently, the design of commercial ships with less green-house gas is one of great interests in naval architecture fields. Ship designers are asked to find optimum hull forms with minimum resistance in ocean waves. The accurate computation of added resistance, therefore, is getting more important for the prediction of power increase in random ocean waves. This study focuses on the numerical computation of added resistance on ships with Ax-bow shapes which are designed to reduce added resistance. To this end, the time-domain Rankine panel methods based on weakly-nonlinear and weak-scatterer approaches are applied, which can reflect the influence of above-still-water bow shape. As computational models, KCS and KVLCC2 hull forms are considered. Each ship is combined with the three types of Ax-bow shape, and computational results are compared each other.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.431-437
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• 2018

The running attitude of a planing hull is determined by the pressure distribution on the hull bottom, and it significantly affects hydrodynamic performance of the ship, i.e., resistance, maneuverability, and seakeeping ability. Therefore, it is essential to investigate pressure distribution on the hull bottom in order to improve hull design. In the present study, a novel pressure measurement system using tactile sensors was introduced for a planing hull. The test model was a 23 m-class planing hull with a hard chine. The pressure measurement showed that the pressure at the transom was lower than the atmospheric pressure, owing to flow separation at the transom.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.27-33
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• 2016

A numerical analysis on deck wetness is carried out for a large caisson directly wet-towed by tugs in irregular waves. A constant panel method is used for linear analysis in frequency domain and a statistical post-processing for the deck wetness is presented. Hydrodynamic coefficients obtained from the frequency domain computation are imported for time domain analysis which enables complete modeling for towing equipment, environment, etc. Both frequency and time domain computations over two sea states are performed and comparison is made. In the time domain analysis, towing systems of various arrangements of tugs are investigated from short-term prediction for the largest deck wetness and the number of occurrences of deck wetness.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.516-527
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• 2011

This paper considers a numerical analysis of ship maneuvering performance in the high amplitude incident waves by adopting linear and nonlinear ship motion analysis. A time-domain ship motion program is developed to solve the wave-body interaction problem with the ship slip speed and rotation, and it is coupled with a modular type 4-DOF maneuvering problem. Nonlinear Froude-Krylov and restoring forces are included to consider weakly nonlinear ship motion. The developed method is applied to observe the nonlinear ship motion and planar trajectories in maneuvering test in the presence of incident waves. The comparisons are made for S-175 containership with existing experimental data. The nonlinear computation results show a fair agreement of overall tendency in maneuvering performance. In addition, maneuvering performances with respect to wave slope is predicted and reasonable results are observed.