• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1995.11a
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• pp.153-165
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• 1995

When an automatic course-keeping is introduced as is quite popular in modern navigation the closed-loop steering system consists of autopilot device power unit(or telemotor unit) steering gear ship dynamics and magnetic or gyro compass. We derive the mathematical model of each element of the automatic steering system. We provide a method of theoretical analysis on propulsive energy loss related to automatic steering of ships inthe open seas taking account of the on-off mechanism of power unit. Also we paid attention to dead band mechanism of autopilot device which is normally called weather adjustment. Next we make numerical calculation of the effects of autopilot control constants ont he propulsive energy loss for two kinds of ship a fishing boat and an ore carrier. Realistic sea and wind disturbances are employed in the calculation.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.2
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• pp.236-242
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• 2005

Dynamic Positioning(DP) system maintains ship's position (fixed location or predetermined track) exclusively by means of CPPs and thrusters. To generate the control input adequate to various situation an integrated controller for CPPs and thrusters is required. The integrated controller is composed of a thrust calculation algorithm and a thrust allocation algorithm. The thrust calculation algorithm generates thrusts in the surge direction and the sway direction from the desired forward and lateral speed and generates a moment about the yaw axis from desired heading angle. The thrust allocation algorithm allocates the generated thrusts and moment to each CPP and thruster. Computer simulations are executed to confirm the effectiveness of the suggested controller.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.137-139
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• 2003

As a part of numerical and experimental research works for the prediction and improvement of ship's maneuvering performance, a study on the performance analysis of two different rudders has been carried out. While the planform shape and the aspect ratio of the rudders have been fixed, section shape has been changed. Conventional type of HMRI NP section and special type of dolphin-tail section have been employed. Performances of the rudders have been investigated by using CFD and compared with experimental data obtained in a wind tunnel. A commercial CFD program has been used to solve the RANS equations. Two-equation k-ro model has been applied to close the governing equations. Block-structured grids are used in the numerical calculation. Based upon the calculation results, the rudder with dolphin-tail section has shown a possibility of significantly improving rudder performance if utilized as the section of ship rudders.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.102-110
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• 1997

In a shipyard, computer calculation is not frequently used for the grain stability calculation because of large difference between calculation values and real values. Therefore, the necessary calculation process for grain stability is done manually. GUI(Graphical User Interface) is adopted for the convenience of users and interactive data I/O. The hold shape (girder, hold, etc.)needed for calculation are visualized using GLBAX which is a 3 dimensional graphic library. The interface with the ship basic calculation package is also implemented. The aim of this paper is to develop a reliable interactive grain stability calculation program which reduces computational time, and is to computerize the grain stability calculation procedure.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.66-75
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• 1993

Flow control devices, such as flow liners, are frequently introduced hi a cavitation tunnel in order to reduce the tunnel blockage effect, when a three-dimensional wake distribution is simulated using a complete ship model or a dummy model. In order to estimate the tunnel wall effect and to evaluate the effect of flow liners on the simulated wake distribution, a surface panel method is adopted for the calculation of the flow around a ship model and flow liners installed in a rectangular test section of a cavitation tunnel. Calculation results on the Sydney Express ship model show that the tunnel wall effect on the hull surface pressure distribution is negligible for less than 5% blockage and can be appreciable for more than 20% blockage. The flow liners accelerate the flow near the after body of the ship model, so that the pressure gradient there becomes more favorable and accordingly the boundary layer thickness would be reduced. Since the resulting wake distribution is assumed to resemble the full scale wake, flow liners can also be used to simulate an estimated full scale wake without modifying the ship model. Boundary layer calculation should be incorporated in order to correlate the calculated wake distribution with tole measured one.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.4
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• pp.528-533
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• 2010

This paper describes a calculation method of source level of a ship transient noise, which is one of the important elements for the ship detection. Aim of transient noise measurements is to evaluate of acoustic energy due to singular occurrence, which is therefore defined as non-periodic and short termed events like an attack periscope, a rudder and a torpedo door. In generally, in the case of randomly spaced impulse, the spectrum becomes a broadband random noise with no distinctive pattern. Therefore, frequency analysis is not particularly revealing for type of signal. In the paper, it is performed in time domain to analyze a transient noise. However, a source level of transient noise is required an investigation for multiple frequency band. So, in order to calculate a source level of transient noise, a design of exponential weighting function, convolution, band pass filtering, peak detection, root mean square, and parameter compensation are applied. The effectiveness of this calculation scheme is studied through computer simulations and a sea test. Furthermore, an application of the method is applied in a real case.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.1
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• pp.35-38
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• 1982

Ship hull Vibration is caused by troubling measure instruments installed in the ship, fatigue of the hull girder. Vibration has been studied by the View point of anti-Vibration. However, the theoretical calculation values of the Vibration analysis were not obtained accurately. Therfore, in this paper, Vibration analysis were made on the two (cylinder form, ship form) of ship hull girder by the transfer matrix method. The super-structure length was determined to be 0, 20, 40, 60, 80, 100, percentage of the ship's length from the stern. The results of analysis by the transfer matrix method are as follow. 1. Natural frequency may be determined by the order of node numbers and superstructure length. 2. Natural frequency inereased when the ship form is a finess and increasing ratio followed by high order of node numbers.

• Journal of Navigation and Port Research
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• v.27 no.6
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• pp.639-643
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• 2003

The emphasis is put on the detailed knowledge on manoeuvring characteristic for the safe navigation while avoiding terrible collision between ships and on the guideline to the design and operation of the ship-waterway system The numerical simulation of manoeuvring motion was carried out parametrically for different ship types, ship-velocity ratios, separation and stagger between ships. As for the calculation parameters, the ratios of velocity difference (hereafter, $U_2$/$U_1$ ) between two ships were considered as 0.6, 1.2, 1.5. From the inspection of this investigation, it indicates the following result. Considering the interaction force only as parameter, the lateral distance between ships is necessarily required for the ship-velocity ratio of 1.2, compared to the cases of 0.6 and 1.5 regardless of the ship types. Furthermore, regardless of the ship-velocity ratio, an overtaking and overtaken vessel can be manoeuvred safely without deviating from the original course under the following conditions: the lateral distance between two vessels is approximately kept at 0.5 times of ship-length and 5 through 10. degrees of range in maximum rudder angle. The manoeuvring characteristic based on this investigation will be very useful for keeping the safety of navigation from the practical point of ships design and traffic control in restricted waterways.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.4
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• pp.686-694
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• 2014

Research on ship motion and seasickness is recognized as the important research area to ensure the pleasant operative environment in addition to the research of operation safety of ship. In this paper, The motion performance in waves for the training ship Kaya of Pukyong National University is obtained by using the computer program based on Strip method. To guarantee the pleasant seafaring in ocean, the vertical acceleration of ship motion is calculated according to the hull form modification. The results of calculation by changes of hull form are compared with the guideline of MSI(Motion Sickness Incidence). The degree of motion sickness is shown and discussed through the comparison between calculated vertical acceleration spectrum and MSI guideline.

• Journal of the Korea Society for Simulation
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• v.10 no.2
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• pp.33-46
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• 2001

Recently, the usage of containers in marine transportation is rapidly increasing. The problem of ship stability is important because of its direct influence to the loss of the human-life, ship, and merchandise. However, the assessment for ship stability during container loading/unloading in port is dependent on human experience only. On the other hand, the emerging information and communication technologies of shipbuilding industrial environments are rapidly changing. To respond to the situation, a new paradigm has been matured with new concepts such as the concrete method. Especially, all the efforts are shown to be concentrated to realize the concept of Simulation Based Design(SBD) based on three dimensional Computer Aided Design(CAD) model. In this paper, ship model-based simulation methodology for design and operation of ship is suggested, and for the verification of suggested methodology, the system for stability assessment of ship during container loading/unloading was developed using ENVISION, a general-purpose simulation system. The developed system consists of geometric modeling subsystem, basic calculation subsystem, and Computer Aided Engineering(CAE) subsystem. In addition, interface to CAE/CAD /simulation system such as SIKOB and ENVISION is provided.