• Journal of Advanced Marine Engineering and Technology
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• v.4 no.1
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• pp.2-22
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• 1980

In the earlier days, when the diesel engine was used for ship propulsion, its shaft had often been broken by uncertain causes. Bauer suggested, for the first time in 1900, that it resulted from the torsional vibration of the shaft system. From 1901 to 1902, Gumbel and Frahm found out that shaft failures were caused by the resonance of the shaft system in critical speed. Since that time, valuable theories, empirical formulae and methods of vibration analysis were introduced by many investigators such as Geiger, Holzer, Lewis, Carter, Porter, Constant, Timoshenko, Dorey, Den Hartog, Tuplin, Ker Wilson, Bradbury etc. But, as the calculation of the damping energy involves very complicated and uncertain factors, the estimated amplitude of the torsional vibration is incorrect and uncertain. Besides, as high-powered engines have been installed on large vessels or special vessels and exciting force has been increased, new problems of the torsional vibration have continuously occurred. Although we can calculate the approximate natural frequencies or estimate their amplitude and additional stress in the design stage, through the above mentioned studies, the results of the calculations are unsatisfactory, and so much time is needed to carry out the calculation by hand. The authors have developed a computer program to calculate its natural frequencies, the amplitudes and additional stresses of the torsional vibration in the marine diesel engine shafting. In developing the computer program, the authors have paid the special attention to the calculation of the damping energy. To verify the reliability of the developed computer program, the torsional vibration of several propulsion shaftings which are driven by the diesel engine has been analyzed. The results calculted by the authors' computer program show good agreements with those of the actual measurements and are better than the results of engine maker's calculation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.101-109
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• 2002

The aluminum honeycomb sandwich panel (AHSP) structure not only have high flexural rigidity and strength per density but also excellence in vibration and noise properties. The AHSP structure are very useful for railway, airplane and high speed ship which need lighter-weighted and more strengthened elements. In this paper, from comparison the AHSP with the equivalent aluminum single plate (EASP) structure on the result of analysis, it was shown that the AHSP is S times lighter weight to the same stiffness than the EASP. And the AHSP structure have high bending rigidity and small shear rigidity in the direction of the thickness. Also, to the characteristics of vibration for the AHSP and EASP, which the stiffness is larger than the EASP, are higher than EASP.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.647-652
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• 2005

When a vessel passes near a channel boundary, the boundary creates forces and moments acting on the vessel. With the same reason passing of two vessels closely gives same effects to each other. The principal difference between the above two cases is that the channel boundary is long and constant shape compared to those of vessels. The interaction forces and moments between two vessels could be assumed to be functions of the longitudinal distance $chi_0$, transverse distance $y_0$ and speeds of the two vessels. Passage of one vessel close to another is important operationally from the viewpoint of replenishment at sea, avoidance of collisions and passage of two vessels in restricted channels. The authors studied the interactions between two vessels running closely and calculated safe conducting distances according to separated distances and speeds of the two vessels.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.199-206
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• 2011

In Korea, the current design codes for the bridge vessel collision load are based on AASHTO LRFD code which derived from the mean collision forces of the Woisin's test. To estimate the conservativeness of the code, in this study, the mean forces of head on collisions were evaluated from the mass-acceleration relationship of vessel and the deformation-kinetic energy relationship of bow those obtained from the series of nonlinear finite element analysis, and the mean forces were compared to that in AASHTO design code. As results, the variations of the mean forces versus the sizes of vessels were represented similar tendency, even those of the code are very conservative. However, the variations of mean collision force versus those of collision speeds were dominated by the plastic deformation of bow and it was differ from those of the code that have linear relationship with the collision speeds.

• Journal of Ocean Engineering and Technology
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• v.32 no.3
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• pp.202-207
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• 2018

This paper presents the efficiency of a floating vertical axis wind turbine with variable-pitch. A model was designed to use the lift force and drag force for blades with various pitch angles. The blade's pitch angle is controlled by the stopper. To validate the efficiency of the wind turbine discussed in this paper, a model test was carried out through a single model efficiency experiment and wave tank experiment. The parameters of the single model efficiency experiment were the wind speed, electronic load, and pitch angle. The wave tank experiment was performed using the most efficient pitch angle from the results of the single model efficiency experiment. According to the results of the wave tank experiment, the surge and pitch motion of a structure slightly affect the efficiency of a wind turbine, but the heave motion has a large effect because the heights of the wind turbine and wind generator are almost the same.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.192-199
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• 2004

Navigation simulators have been used in many marine schools and manne training centers since the early 1960's. But these simulators were very expens~ve and were almost limited only in one engine system. In this paper, a catamaran with twin engine system. controlled by two remote control levers and its economic simulator based on a personal computer shall be introduced. One of the main features of catamaran is to control variously its progressing direction. In the static state, a catamaran can move into all the directions and in the dynamic state, ship can change immediately the heading and speed. Although a good navigator can skillfully operate one engine system, it is difficult to control smoothly the catamaran of twin engine system without any threat for the safety of passengers. Thus. in order to bring up the expert navigators. the development of a simulator which makes the training effective is necessary, Therefore, in this paper, a Fuzzy Inference Technique based Maneuvering Simulator for catamaran with twin engine system was developed. In general. in order to develop a catamaran simulator for effective training, first of all. its mathematical model must be acquired. According to the acquired system modeling. the dynamics of simulator is determined, But the proposed technique can omit a complex and tedious mathematical modeling procedures by using the fuzzy inference, which dependent upon only experiences of an expert and can design an efficient training program for unskillful navigators. This developed simulator was consisted of two fuzzy inference routines and two remote control levers, and was focused on effective training of navigators for the safe maneuvering to avoid a collision in a harbor.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.447-452
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• 2013

Vessel traffic system uses multiple sea surveillance radars as a primary sensor to obtain maritime traffic information like as ship's position, speed, course. The systematic errors such as the range bias and the azimuth bias of the two-dimensional radar system can significantly degrade the accuracy of the radar image and target tracking information. Therefore, the systematic errors of the radar system should be corrected precisely in order to provide the accurate target information in the vessel traffic system. In this paper, it is proposed that the method compensates the range bias and the azimuth bias using AtoN information installed at VTS coverage. The radar measurement residual error model is derived from the standard error model of two-dimensional radar measurements and the position information of AtoN, and then the linear Kalman filter is designed for estimation of the systematic errors of the radar system. The proposed method is validated via Monte-Carlo runs. Also, the convergence characteristics of the designed filter and the accuracy of the systematic error estimates according to the number of AtoN information are analyzed.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.159.2-159.2
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• 2011

Hyundai Heavy Industries has developed a tidal current energy converter utilizing the accumulated technology as the world largest constructor for ship and offshore structures. The model has two sets of turbines in both ends in order to utilize the bi-directional current flows in flood and ebb tide. The torque produced by turbine in tidal current is directly delivered to generator along the horizontal axis, in which the turbine, gear, generator, gear and turbine are connected successively. The manufactured model for field test has the turbine diameter of 5 meters to produce the maximum power of 500kW at maximum current speed of 5m/s. The technical verification of tidal power converter was performed by means of small scale model test in towing tank as well as field test at the Strait of Uldolmok located in Jindo of Jeollanamdo province. Field test was performed by mounting the tidal current converter on the SEP(Self Elevating Platform) which could lower the 4 vertical legs on the seabed and could elevate platform over the water surface using the hydraulic power for itself. The field test performed for a month shows that power output is similar or larger compared with the expected one in design stage. This paper presents the development of tidal current energy converter and real sea field test by Hyundai Heavy Industries. This project has finished successfully and provided the technical advance toward commercial services for tidal current power generation in the south-west region in Korea.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.326-334
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• 1994

This paper describes the fabrication of the hydrophilic magnetic fluid with high viscosity and its application to oil seal apparatus used with the Nd-permanent magnet. The results are as follows. 1) The ultrafine magnetite particles under the size of $100\;{\AA}$ are first coated by the oleic acid ion and again adsorbed by the hydrophilic D. B. S. ion, and there by hydrophilic magnetic fluid with high viscosity could be made by dispersing them into the ethylene glycol. 2) In development of the oil seal apparatus using magnetic fluid and Nd-permanent magnet, the viscosity and magnetic susceptibility show high when the $Fe_{3}O_{4}$ content is over 50%(g/cc) in the fluid, so that such properties could improve highly the capability of oil seal. 3) The maximum of the resisting pressure of the oil seal using the ethylene glycol base magnetic fluid and the Nd-permanent magnet, is about $50\;g/\textrm{cm}^2$, under the condition of this experiment. Therefore the oil seal may not be suitable for the ship engine and the driving part of the automobile, and thus it needs a lot further complementary reserch. However, it is quite favourable for such an oil seal apparatus as speed reducer under the condition of atmospheric pressure.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.37-43
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• 2005

Recently, many ships such as fishing boats, cargo ships, high speed ferry boats are visiting Mokpo harbor. In particular, many marine accidents rave been occurred at this area because of the narrow channel, a thick fog, the existing of the shallow waters etc. However there is no suitable ships' routeing system which takes account of today's traffic situations in this area. This study aims at the settling of hazardous factors to mitigate the danger to vessels in mokpo harbor and to secure the safety qf maritime environment.