• Special Issue of the Society of Naval Architects of Korea
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• 2007.09a
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• pp.74-78
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• 2007

In this paper, the HPMM(Horizontal Planar Motion Mechanism) test is simulated in a numerical towing tank by using a commercial CFD(Computational Fluid Dynamics) code, FLUENT. The results of calculation are compared with those of static drift test or rotating arm test calculated by CFD to verify the results simulated by CFD. Through comparing pure sway test of HPMM test with static drift test and pure yaw test of HPMM with rotating arm test, it is found that HPMM test can be simulated in the numerical towing tank.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.5
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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.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.3
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.372-379
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• 1998

A new 6 degrees-of-freedom micro stage, based on parallel mechanisms and actuated by using piezoelectric elements, has been developed for the application of micro positioning such as semiconductor manufacturing devices, high precision optical measurement systems, and high accurate machining. The micro stage structure consists of a base platform and an upper platform(stage). The base platform can effectively generates planar motion with yaw motion, while the stage can do vertical motion with roll and pitch motions with respect to the base platform. This separated structure has an advantage of less interference among actuators. The forward and inverse kinematics of the micro stage are discussed. Also, through linearization of kinematic equations about an operating point on the assumption that the configuration of the micro stage remains essentially constant throughout a workspace is performed. To maximize the workspace of the stage relative to fixed frame, an optimal design procedure of geometric parameter is shown. Hardware description and a prototype are presented. The prototype is about 150mm in height and its base platform is approximately 94mm in diameter. The workspace of the prototype is obtained by computer simulation. Kinematic calibration procedure of the micro stage and its results are presented.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.31-37
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• 1990

To obtain the values of linear stability derivatives, both analytical and experimental methods are now proposed and in use. The experimental method is well known as the planar motion mechanism(PMM) test. Its concept is to drive the model with a prescrived frequency and amplitude of the motion and pick up the hydrodynamic forces. But this kind of method is inconvenient in case we want to know the stability derivatives in wider range of the frequencies. So a different method is attempted that with one test run, we can get the derivatives in wider range of the frequencies. This technique forces the impulsive motion on the model, using the power of the oil pressure pump. This kind of method was originated by Scragg, C.A., Cummins, W.E, or Frank, T., This resarch is a further development of such preceding works. Todd's series 60(Cb=0.7) 2.00M model is chosen for the test and the results are compared with Van Leeuwen's famous PMM test results.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.6
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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.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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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.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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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.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.5
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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.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.6 s.144
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• pp.551-558
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• 2005

In this paper, horizontal manoeuvrability of an underwater vehicle near free surface was investigated. Planar Motion Mechanism(PMM) tests were performed at the shallow depth within 4.5 times of vehicle's diameter. Hydrodynamic coefficients related to the horizontal movement were estimated from the measured data using Least SQuare(LS) method and analyzed at each submerged depth. Furthermore, horizontal dynamic stability, trajectory of turning and zigzag test were investigated for the various depths. As underwater vehicle is positioned nearer to the free surface, forces increase and moment decreases. Tested model was found to be stable only at the depth 0.5 times of vehicle's diameter.