• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.466-477
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• 2015

In this study, a numerical prediction method on manoeuvrability of Wind Turbine Installation Vessel (WTIV) is presented. Planar Motion Mechanism (PMM) captive test for the bare hull of WTIV is carried out in the model basin and compared with the numerical results using RANS simulation based on Open-source Field Operation And Manipulation (OpenFOAM) calculation to validate the developed method. The manoeuvrability of WTIV with skeg and/or without skeg is investigated using the numerical approach along with the captive model test. In the numerical calculations, the dynamic stability index which indicates the course keeping ability is evaluated and compared for three different hull configurations i.e. bare hull and other two hulls with center skeg and twin skeg. This paper proves that the numerical approach using RANS simulation can be readily applied to estimate the manoeuvrability of WTIV at the initial design stage.

• 대한조선학회논문집
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• 제43권1호
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• pp.15-21
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• 2006

Recently, the attention to large container ships whose size is greater than 10,000 TEU container ship has been increased due to their increasing demand. The large container ship has twin skegs because of the engine capacity and large beam-draft ratio. In this paper, the maneuvering characteristics of a container ship with twin skegs were investigated through 4DOF(four degree of freedom) HPMM(Horizontal Planar Motion Mechanism) test and computer simulation. A mathematical model for maneuvering motion with 4DOF of twin skegs system was established to include effects of roll motion on the maneuvering motion. And to obtain roll-coupling hydrodynamic coefficients of a container ship, 4DOF HPMM system of MOERI which has a roll moment measurement system was used. HPMM tests were carried out for a 12,000 TEU class container ship with twin skegs at scantling load condition. Using the hydrodynamic coefficients obtained, simulations were made to predict the maneuvering motion. Rudder forces of twin-rudders were measured at the angles of drift and rudder. The neutral rudder angles with drift angles of ship was quite different with those of single skeg ship. So other treatment of flow straightening coefficient $\gamma_R$ was used and the simulation results was compared with general simulation result. The treatment of experimental result at static drift and rudder test was very important to predict the maneuverability of a container ship with twin skegs.

• 대한조선학회지
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• 제27권3호
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• pp.31-37
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• 1990

선박의 방향안정성 등을 논할 때 필요하게 되는 선형조종미계수에 대해서는 이론적, 실험적으로 그 추정법이 제안되고 있다. 이중, 실험적 방법은 모형선에 규칙적인 강제동요를 시켜서 원하는 값들을 구하고 있으나, 한규칙 동요에 대해서 그 주파수에 대한 값만 나오므로 넓은 범위의 운동주파수에 걸쳐 미계수의 값들을 얻고자 할 때는 방대한 회수의 실험을 행해야 한다, 이러한 단점을 개선하기 위해 고안된 것이 본 논문에서 취급하는 Transient Maneuvering Method(TMM)로서, 기본원리는 모형에게 과도적 운동을 시켜 그로 인한 동유체력을 계측하고 이를 Fourier 변환하므로서 여러가지 주파수에 대한 미계수의 값을 얻게 되는 것이다. 종래의 이 분야 연구자들은 모형을 움직일 때 전동모터를 사용했으나 모터를 사용할 경우 원하는 과도 운동을 충분히 시킬 수 없으므로 본 논문에서는 유압 펌프를 사용하여 좋은 효과를 얻었다. 그 외에도 입력신호를 다소 개량하여 최종결과의 S/N비를 개선하는데 성공하였다. 실험에 사용한 모델은 Todd의 계열 60(Cb=0.7) 2M급이고, 이 결과를 종래의 PMM 시험결과와 비교하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권5호
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• pp.848-872
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• 2015

Hydrodynamic derivatives or coefficients are required to predict the maneuvering characteristics of a marine vehicle. These derivatives are obtained numerically for a DTMB 5512 model ship by virtual simulating of captive model tests in a CFD environment. The computed coefficients are applied to predict the turning circle and zig-zag maneuvers of the model ship. The comparison of the simulated results with the available experimental data shows a very good agreement among them. The simulations show that the CFD is precise and affordable tool at the preliminary design stage to obtain maneuverability performance of a marine vehicles.

• 한국해양공학회지
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• 제25권1호
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• pp.27-31
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• 2011

The previously developed method of estimating the propulsion performance of a UUV was applied to the high speed UUV, which is propelled by commercial thrusters. The thrusters were selected with an overdesign mentality; in other words, their capacities were excessive. At that point, the designer's concern was focused on a question regarding at what rpm the UUV could reach the design speed. Because the developed method required thrust coefficient curve data, the researchers asked for the POW data of the thrusters from the manufacturer. From the data, the researchers extracted the thrust coefficient and estimated the rpm value of design speed for the UUV. Finally, the researchers compared the estimated value and the result from a self-propulsion test using a VPMM (Vertical planar motion mechanism) test at a towing tank in MOERI.

• 대한조선학회논문집
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• 제52권5호
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• pp.407-417
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• 2015

For the more accurate prediction on manoeuvring performance of a ship at initial design phase, bare hull manoeuvring coefficients were estimated by RANS(Reynolds Averaged Navier-Stokes) based virtual captive model tests. Hydrodynamic forces and moment acting on the hull during static drift and harmonic oscillatory motions were computed with a commercial RANS code STAR-CCM+. Automatic and consistent mesh generation could be implemented by using macro functions of the code and user dependency could be greatly reduced. Computed forces and moments on KCS and KVLCC 1&2 were compared with the corresponding measurements from PMM(Planar Motion Mechanism) tests. Quite good agreement can be observed between the CFD and EFD results. Manoeuvring coefficients and IMO standard manoeuvres estimated from the computed data also showed reasonable agreement with those from the experimental data. Based on these results, we could confirm that the developed virtual captive manoeuvring model test process could be applied to evaluate manoeuvrability of a ship at the initial hull design phase.

• 한국항해항만학회지
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• 제36권8호
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• pp.613-618
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• 2012

부선이 선미 예인되는 상황에서의 예부선 통합시뮬레이션을 수행하기 위하여, 본 연구에서는 부선 단독 조종성능 추정을 위한 구속모형실험을 수행하였다. 구속모형실험결과로부터 부선 실선의 저항성능을 추정하였고, 도출된 유체력 미계수를 이용하여 선회시뮬레이션을 수행하였다. 부선의 선회시뮬레이션을 위해 부선에 작용하는 예인력의 힘과 방향을 단순히 모델링하고, 예인줄 방향각 변화에 따른 선회시뮬레이션 결과 비교와 실선시운전시험결과와의 선회직경 비교를 통하여 수학모델을 검증하였다. 그 결과 예인줄 방향각이 커질수록 선회직경이 작아지는 정성적인 경향을 확인하였고, 실선시운전결과와 비교 시 배수량 차이 등에 의하여 선회직경이 작게 추정되는 결과를 확인하였다.

• 대한조선학회논문집
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• 제35권1호
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• pp.46-53
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• 1998

본 논문은 초기 설계단계에서 조종성능추정에 널리 사용되고 있는 Inoue 및 Kijima 추정법을 개선하였다. 이를 위하여 당연구소는 Horn 형태의 타와 선미벌브 형태를 갖는 저속비대선에 대해 12척의 계열 PMM 시험과 타단독시험을 수행하였다. 조종수학모델은 일본에서 개발된 MMG 방법을 사용하여 유체력미계수 및 MMG 실험 계수를 해석하였고, 그 결과를 이용하여 기본제원에 의한 회귀분석을 수행하여 민감도 조사 및 조종성능 해석을 수행하였다. 본 논문의 유효성을 검토하기 위해 개선된 회귀식으로 조종성능 해석을 수행하고 그 결과를 Inoue 추정법, PMM 시험에 의한 추정법 및 실선 시운전 결과를 서로 비교하였다.

• 대한조선학회논문집
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• 제51권6호
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• pp.539-547
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• 2014

Ship squat is a well known phenomenon, which means an additional sinkage and a change of trim when a ship sails in shallow water. As a series of ship squat study, a HPMM(Horizontal Planar Motion Mechanism) test of KVLCC2 model ship to measure a sinkage and a trim in shallow water was conducted. Additionally a CFD(Computational Fluid Dynamics) analysis was carried out to simulate fluid flows around the ship surface. A change in ship speed, drift angle at three depth conditions(H/T = 1.2, 1.5 & 2.0) is considered for comparing these results. As a result, an increase of the ship speed and the drift angle caused an increase in ship squat in EFD(Experimental Fluid Dynamics), and created a lower pressure on the ship bottom area in CFD. Lastly the sinkage results of KVLCC2 by EFD and CFD are compared to results by three empirical formulas. The tendency of sinkage by EFD and CFD is similar to the results of empirical formulas.

• 한국생산제조학회지
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• 제24권2호
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• pp.141-147
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• 2015

In this study, a position control algorithm for an omni-directional mobile robot based on Mecanum wheels was introduced and experimentally evaluated. Multiple ultrasonic sensors were installed around the mobile robot to obtain position feedback. Using the distance of the robot from the wall, the position and orientation of the mobile robot were calculated. In accordance with the omni-directional velocity generation mechanism, the velocity kinematics between the Mecanum wheel and the mobile platform were determined. Based on this formulation, a simple and intuitive position control algorithm was suggested. To evaluate the control algorithm, a test bed composed of artificial walls was designed and implemented. While conventional control algorithms based on normal wheels require additional path planning for two-dimensional planar motion, the omni-directional mobile robot using distance sensors was able to directly follow target positions with the simple proposed position feedback algorithm.