• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1932-1934
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• 2001

In this paper, a horizontal LOS(line of sight) rate estimator for conventional sea skimming ASM(anti-ship missile) is proposed. A LOS rate dynamics model in 2 axis gimbal system and in homing geometry is derived. And a new LOS rate estimator is proposed by applying a Kalman filter theory to the LOS rate dynamics model. The proposed filter can estimate LOS rates with taking roll motions into account. Simulation results show the proposed filter produces smaller estimation errors than a conventional method.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.16-21
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• 2003

The very large container ships have been built recently and those ships have very small structural rigidity compared with the other conventional ships. As a result, the destruction of ship hull is occurred by the springing including to warping phenomena due to encounter waves. In this study, the solutions of hydrodynamic coefficients are obtained by solving the three dimensional source distribution method and the forward speed Green function representing a translating and pulsating source potential for infinite water depth is used to calculating the integral equation. The vessel is longitudinally divided into various sections and the added mass, wave damping and wave exciting forces of each section is calculated by integrating the dynamic pressures over the mean wetted section surface. The equations for six degree freedom of motions is obtained for each section in the frequency domain and stiffness matrix is calculated by Euler beam theory. The computations are carried out for very large ship and effects of bending and torsional ridigity on the wave frequency and angle are investigated.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.119-122
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• 2007

The sloshing flows in the cargo tank model of a ship are measured by PIV and are analyzed with the results. The measurement system is consisted of a Nd-Yag laser(120mJ, 15Hz). two cameras($1k\;{\times}\;1k$) and a host computer. Four experimental cases were tested for the tank model. in which swaying motions are made by 6 DOF-motion platform. The amplitudes of swaying are 9.76mm and 29.29mm, and the frequencies are 0.633Hz and 0.828Hz. The measurement regions are the vertical plane 50mm away from the front wall of the tank where a pump tower is installed. It was verified that the flow patterns of the sloshing are similar each other when the swaying amplitudes are similar.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1982-1992
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• 1999

This paper presents a novel concept of cargo handling system adapted for a sea port subjected to severe time-varying tide. The proposed system can perform loading or unloading by using a sort of hydraulic elevator associated with real-time position control. In order to achieve a proof-of-concept, a small-sized laboratory model of the cargo handling system is designed and built. The model consists of three principal components container palette transfer (CPT) car, platform with lifting columns, and cargo ship. The platform activated by electro-rheological (ER) valve-cylinders is actively controlled to track the position of the cargo ship subjected to be varied due to the time-varying tide and wave motion. Following the derivation of the dynamic model for the platform and cargo ship motions, an appropriate control scheme is formulated and implemented. The location of the CPT car is sensed by a set of photoelectric switches and controlled via sequence controller. On the other hand, a sliding mode controller (SMC) is adopted as the position controller for the platform. Both simulated and measured control results are presented to demonstrate the effectiveness of the proposed cargo system.

• Journal of Ocean Engineering and Technology
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• v.18 no.3
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• pp.8-12
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• 2004

The anchor is laid on the seabed, and the main engine is working against incident environmental loads in a typhoon. As the main engine is broken Mum in the storm, the anchor chain is cut and the vessel drifts. Although a ship is moored by two-point mooring lines to maintain her position, it has crashed into a rock because of a typhoon, resulting in a possible accidental oil spillage. In this paper, we studied maintenance of a ship's position, which is analyzed based on the slow motion maneuvering equations considering wave, current, and wind. To estimate wave loads, the direct integration method is employed. The current forces are calculated, using MMG (Mathematical Modeling Group). Th two-point mooring forces are quasi-statistically evaluated, using the catenary equation. Th coefficients of wind forces are modeled from Isherwood's empirical data, and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two-point moored ship are simulated, considering wave, current, and wind load, in specific domain of time.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.1
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• pp.47-57
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• 2019

Recent CFD solvers in engineering have to treat geometrically complex domains and moving body problems. In ship hydrodynamics, flow around the stern and ship motions in waves are examples of such cases mentioned before. The unstructured grid scheme is successfully applied for these problems, but it has weakness of inefficient memory usage and intensive computational time as compared to the structured grid method. Overset grid scheme is one of the alternatives for structured grid system taking advantage of fast and memory efficiency. Overset grid scheme is especially useful for moving body problem because there is no need to re-mesh around the body. In this paper, we adopted the Suggar++, the grid connectivity and interpolation utility for the overlapping grid, to WAVIS which is the in-house flow solver of KRISO. Then we introduced some applications using the overset grid method for flow analysis around the ships. The computed results show that WAVIS with Suggar++ is practically feasible and has an advantages for moving geometry cases.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_1
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• pp.907-915
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• 2020

Specification selection, Layout, specifications and combinations of Power Drives, and Ship motions were studied for FGPP(Floating Gas-fired Power Plants), which are still needed in areas such as the Caribbean, Latin America, and Southeast Asia where electricity is not sufficiently supplied. From this study, the optimal equipment layout in ships was derived. In addition, the difference between engine and turbine was verified through LCOE(Levelized Cost of Energy) comparison according to the type and combination of Power Drives. Analysis of Hs(Significant Height of wave) and Tp(spectrum Peak Period of wave) for places where this FGPP will be tested or applied enables design according to wave characteristics in Brazil and Indonesia. Normalized Sloshing Pressures of FGPP and LNG Carrier are verified using a sloshing analysis program, which is CFD(Computational Fluid Dynamics) software developed by ABS(American Bureau of Shipping). Power Transmission System is studied with Double bus with one Circuit Breaker Topology. A nd the CFD analysis allowed us to calculate linear roll damping coefficients for more accurate full load conditions and ballast conditions. Through RAO(Response Amplitude Operator) analysis, we secured data that could minimize the movement of ships according to the direction of waves and ship placement by identifying the characteristics of large movements in the beam sea conditions. The FGPP has been granted an AIP(Approval in Principle) from a classification society, the ABS.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.116-118
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• 2023

In recent years, the need for economical and sustainable ship routing has emerged due to the enforced regulations on environmental issues. Despite the development of weather forecasting technology, maritime accidents by rough waves have continued to occur due to incorrect weather forecasts. In this study, onboard measurements are conducted to observe the acutal situation on merchant ships in operation encountering rough waves. The types of measured data include information related to navigation (Ship's position, speed, bearing, rudder angle) and engine (engine revolutions, power, shaft thrust, fuel consumption), weather conditions (wind, waves), and ship motions (roll, pitch, and yaw). These ship experiments was conducted to 28,000 DWT bulk carrier, 63,000 DWT bulk carrier, 20,000 TEU container ship, and 12,000 TEU container ship. The actual ship experiment of each ship is intended to acquire various types of data and utilize them for multi-objective studies related to ship operation. Additionally, in order to confirm the sea conditions, the directional wave spectrum was reproduced using a wave simulation model. Through data collection from ship experiments and wave simulations, various studies could be proceeding such as the measurement for accurate wave information by marine radar and analysis for cargo collapse accidents. In addition, it is expected to be utilized in various themes from the perspective of safety and efficiency in ship operation.

• Journal of Navigation and Port Research
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• v.32 no.1
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• pp.15-22
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• 2008

A ship in a sea cruises with rolling, pitching, heaving etc because of environmental causes such as wind and wave. Those motions make crews or passengers feel inconvenience and they feel acceleration changes. Therefore, if lateral and vertical accelerations can be measured at a specific position in a ship, it can be known how discomfortable crews or passengers are. The motion monitoring system developed in this paper consists of measuring and communicating part including five accelerometers and gyro and a main computer which acquires measuring data and calculates motion indices. MSI(Motion Sickness Incidence) and MII(Motion Induced Interrupt) are calculated in real time using measured acceleration and angular rate. The validity of the developed system was confirmed through the real ship test of Hannara which is the school ship of Korea Maritime University.

• Journal of Navigation and Port Research
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• v.32 no.5
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• pp.333-339
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• 2008

When a vessel is underway in a heavy weather, passengers and crew suffer from seasickness caused by ship motions such as pitch, heave or roll, or all combined Sickness induces drowsiness, dizziness, headache, stomachache etc, in extreme conditions, they are met with a serious trouble which is physiologically unrecoverable. It results in weakening of spiritual activities or making errors from decrease of motivation, dropping off skills, poor recognition and poor judgement. In this paper, it was examined the international standards concerning the occurrence of sickness and the execution of works, also evaluated the boarding comfort by conducting several times of questionnaire on cadets boarding on the training ship HANBADA As a result, it was confirmed that the main factor of occurring the sickness was the vertical acceleration and the level was more than 0.2g. Also, it was presented the way how to reduce the sickness by changing the speed and/or course in relation to the encounter period.