• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.48-54
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• 2011

Structural modifications of a ship may cause a fatal accident such as sinking and wrecking of ship. Especially, barge ship can be easily reconstructed to load more bulk cargo. In this study, for a real accident case, change of mooring force due to structural modification was analyzed to evaluate accident risk. A two dimensional dynamic model for the barge ship was constructed to compute mooring forces with related to floating motion. The equation of motion was established in Matlab code and buoyancy was calculated by using direct integration of submerged volume. The results showed that wind force, current force, and mooring force after rebuilding was approximately 4.3 kN, 14 kN, 1,561 kN respectively. The maximum force of mooring force according to the length of mooring cable were 1,614 kN at 30 m of mooring cable. Thus, an arbitrary modification of ship lead instability and unreliable result so that illegal rebuilding of ship should be avoided.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.90-103
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• 1997

A numerical procedure is described for predicting the motion and structural responses of the very large floating offshore structures supported by multiple 3-D floating bodies of arbitrary shape in multi-directional irregular waves. The developed numerical approach taking into account of the hydrodynamic interactions among the multiple floating bodies is based on a combination of the 3-D source distribution method, the wave interaction theory, the finite element method and the spectral analysis method to get the significant values of the dynamic responses in the multi-directional irregular waves. The effects of wave interactions and directionality on the dynamic responses of a very large offshore structure, which is semisubmersible ring type, are numerically examined.

• Journal of Navigation and Port Research
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• v.26 no.4
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• pp.441-447
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• 2002

The importance of utilization of ocean space is increased due to high population and narrow land space. The development of a new technology for future use of ocean space, such as a design technology of Very Large Floating Structures(VLFS) is needed. This paper introduces the rime history analysis of superstructures on very large floating structures and proposes the estimation method of time displacement history considering wave loads. The dynamic responses of superstructure according to variation of period and amplitude are analysed using an example frame structure and the dynamic structural safety of VLFS pilot superstructure is evaluated.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2109-2112
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• 2007

독도는 울릉도에서도 동남쪽으로 약 87.4km 떨어져 외해의 영향을 많이 받고 있는 지역이지만 방파제 등 외곽시설이 전무하여 평상파랑에도 접안이 어려운 경우가 많아서 독도 관광자원 활용도 및 편의시설 제공면에서 많은 어려움이 있다. 이에 본 연구에서는 독도 접안시설의 전면에 최근 국내에 본격적으로 도입되고 있는 부방파제(floating breakwater)를 설치할 경우 고정식 방파제 설치에 따른 문제점을 충분히 개선할 수 있다고 판단하여, 부방파제 설치에 따른 기술적인 타당성과 부두 이용률 개선효과 등을 연구 하였다. 독도의 접안시설은 해역이 동도와 서도에 의해 북쪽은 일부 차폐되고 남쪽은 직접 노출되어 있는 지리적 특성이 있어 주 파향인 남쪽계열의 8개 파향(SE, SSE, S, SW, SSW, WSW, W, WNW)의 평상파 제어가 가능하도록 방파제를 배치하였고, 이에 따른 부두 이용률 검토결과 부방파제를 설치할 경우 남쪽계열 파랑에 대하여 현상태에 비하여 부두 이용률이 대략 2배정도 증가되는 것으로 나타났으며, 부방파제 계류시스템의 안정에 대해서도 부체에 영향을 주는 외력에 대하여 계류체인의 길이와 Anchor Block 자중의 규모를 적당히 조정하면 충분히 안정한 것으로 검토되었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.3
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• pp.182-190
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• 1993

A numerical technique is presented to calculate the motions of 6 d.o.f and mooring tensions for a catenary moored floating breakwater. The breakwater may be subjected to the 3-D combination of regular or irregular waves and stationary forces. The added mass coefficients at the infinitive frequency of input wave and the variations of damping and exciting force coefficients are calculated using the source distribution method. The coefficients are used to constitute motion equations in time domain which are solved by WiIson-$\theta$ method. The solutions agree quite well with either static displacement determined from Newton method under the stationary force only or 6 d.o.f determined from the frequency domain analysis under regular wave only. An example analysis is also done for a floating breakwater to demonstrate its applicability.

• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.5-11
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• 2015

Ocean waves have huge amounts of energy, even larger than wind or solar, which can be extracted by some mechanical device. This can be done by creating a system of reacting forces, in which two or more bodies move relative to each other, while at least one body interacts with the waves. This moves the floater up and down. The floaters are connected to an arm structure, which are mounted on a fixed hull structure. Hence, the structure of the floater is very important. A static structural analysis with FSI (Fluid-Structure Interaction) analysis is conducted. To achieve the pressure load for the FSI analysis, the floater is simulated on a wave generator using rigid body motion. The structural analysis is done to examine the stresses on the whole system, and four types of flange and floater are optimized. The result shows that the structure of floater with wood support is the safest.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.67-73
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• 2005

The characteristics of the floating breakwater is briefly reviewed and their performance is numerically investigated. The numerical scheme is a boundary integral method for inviscid potential flows, and various two-dimensional floating breakwater modules are studied focusing on the transmission coefficient. The general characteristics of pontoons is studied as function of mooring line stiffness, mass moment inertia and draft. Trapezoidal-, hat- and table-shape cross-sections are also studied with varying shape-parameters. The efficiency varies with changes in each shape-parameter and for some cases satisfying tranquility can be expected with even longer waves.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.358-363
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• 2017

The high intercept probability depends on optimization of the system, which consists of target detection, tracking system, missile system and so on. To reduce the complexity of global optimization of the system performance, simplification of the relative dependances of each sub-system is done and design parameters for DACS configuration are identified. The conceptual design process is addressed based on the requirement of the design parameters and new methodology is suggested for higher performance.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.40-47
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• 2019

This paper proposes the environment construction and test method of system integration laboratory (SIL) and system integration test (SIT) for verification of interface between onboard equipment and ground control equipment of unmanned aerial systems (UAS). This research also describes the interface environment between subsystems built in SIL and verification methods for the systems' operation logic through simulated flights. Similarly, the paper handles the ground integration test process of UAS in the real testing environments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.235-243
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• 1991

This paper is concerned with developing infinite elements which are applicable to wave diffraction and radiation problems in the vertical plane. The near need region surrounding the solid body is modeled using conventional finite elements. but the far fold region is represented using the infinite elements developed in this study. The shape functions for the infinite elements are derived from the analytical eigenseries solution of the scattered waves in the far field region. The system matrices of the elements are constructed by performing the integration in the infinite direction analytically to achieve computational efficiency. Numerical analysis is carried out for two floating bodies with different cross-sectional shapes to prove the efficiency and validity of the elements. Numerical experiments are also performed to determine the suitable location of the infinite elements which directly affect accuracy and efficiency of the solution.