• 한국해양공학회지
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• 제30권2호
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• pp.84-90
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• 2016

In this study, a six degree-of-freedom motion analysis of a wind-wave hybrid platform equipped with numerous wave energy converters (WECs) was carried out. To examine the effect of the WECs on the platform, an analysis of one-way coupling was carried out, which only considered the power take-off (PTO) damping of the static WECs on the platform. The equation of motion of a floating platform with mooring lines in the time domain was established, and the responses of the one-way coupled platform were then compared with the case of a platform without any coupling effects from the WECs. The hydrodynamic coefficients and wave exciting forces were obtained from the 3D diffraction/radiation pre-processor code WAMIT based on the boundary element method. Then, an analysis of the dynamic responses of the floating platform with or without the WEC effect in the time domain was carried out. All of the dynamics of a floating platform with multiple wind turbines were obtained by coupling FAST and CHARM3D in the time domain, which was further extended to include additional coupled dynamics for multiple turbines. The analysis showed that the PTO damping effect on platform motions was negligible, but coupled effects between multiple WECs and the platform may differentiate the heave, roll, and pitch platform motions from the one without any effects induced by WECs.

• 한국항해항만학회지
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• 제43권6호
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• pp.344-352
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• 2019

초심해역 자원개발용 라이저와 계류된 부유체와의 연성해석을 수행한다. 일반적으로 라이저의 안전성은 부유체와의 연성해석 없이 최대 offset을 고려한 해석을 통해 보수적으로 평가되는데, 본 연구에서는 계류된 부유체의 연성 운동해석을 고려하여 라이저의 안전성을 분석한다. 라이저는 초심해역에 적용되는 SLWR이 고려되며, 부유체는 FPSO가 적용된다. 연성을 고려하는 방법과 고려하지 않는 방법론에 대하여 제시한다. 계류선이 모두 안전한 정상상태(Intact) 조건과 사고(damaged) 조건을 고려하여, 각 조건에서 파랑 입사각도에 따라 연성해석 효과를 분석한다. 하중 조건에 따라 계류선의 장력, 부유체의 운동 및 라이저의 거동 등을 분석한다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2009년도 공동학술대회
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• pp.30-31
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• 2009

본 연구의 목적은 쾌속여객선과 수중부유물과의 실선 충돌응답해석을 통하여 선체와 승객의 내충격 안전성 평가를 수행하는 것이다. 그동안 수중부유물과의 충돌사고로부터 발생하였던 선체와 승객들의 손상자료들을 면밀히 검토하고 평가하여 쾌속여객선 수중익 시스템의 수중부유물과의 충돌에 의한 손상구조를 철저히 파악함으로써 내충격 안전성 평가를 위한 다양한 충돌 시나리오를 작성할 수 있었다. 주변 유체를 고려하는 LS-DYNA 코드의 유체-구조 연성 해석기법과 국부 zooming 해석기법을 사용하여 쾌속여객선의 수중부유물과의 충돌응답해석을 수행하여 선체와 승객의 내충격 안전성 평가를 수행하였다.

• 대한조선학회논문집
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• 제42권5호
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• pp.493-498
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• 2005

Underwater explosion shock response analysis of a MIL-S-901D Standard Floating Shock Platform(SFSP) was performed using LS-DYNA/USA, and the accuracy of analysis results was examined through the comparison of them with the existing test results. Surrounding fluid as well as the SFSP was included In a three dimensional finite element model for the consideration of the cavitation effects of UNOEX shock wave. It was confirmed that the analysis results could predict accurately the shock behaviors of the SFSP, and the response characteristics according to heavy weight shock tests could be figured out well.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.241-248
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• 2004

In general, the salient features if the floating breakwater have excellent regulation of sea-water keeping the marine a1ways clean, up and dorm free movement with the incoming and outgoing tides, capable of being installed without considering the geological condition of sea-bed at any water depth, This study discusses the three dimensional wave transformation of the floating breakwater moored by catenary. Numerical method is based at the Green function method and eigenfunction expansion method. The validity of the present is confirmed by comparing it with the result of Ijima et a1.(1975) fer tensile maxed floating breakwater. According to the numerical results, drift and width of the floating breakwater affect at the wave transformation greatly, and incident wave of long period is well transmitted to the rear of the floating breakwater.

• Structural Engineering and Mechanics
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• 제63권1호
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• pp.37-46
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• 2017

This paper is concerned with the numerical study on the resonance response of a rigid spar-type floating platform in coupled heave and pitch motion. Spar-type floating platforms, widely used for supporting the offshore structures, offer an economic advantage but those exhibit the dynamically high sensitivity to external excitations due to their shape at the same time. Hence, the investigation of their dynamic responses, particularly at resonance, is prerequisite for the design of spar-type floating platforms which secure the dynamic stability. Spar-type floating platform in 2-D surface wave is assumed to be a rigid body having 2-DOFs, and its coupled dynamic equations are analytically derived using the geometric and kinematic relations. The motion-variance of the metacentric height and the moment of inertia of floating platform are taken into consideration, and the hydrodynamic interaction between the wave and platform motions is reflected into the hydrodynamic force and moment and the frequency-dependent added masses. The coupled nonlinear equations governing the heave and pitch motions are solved by the RK4 method, and the frequency responses are obtained by the digital Fourier transform. Through the numerical experiments to the wave frequency, the resonance responses and the coupling in resonance between heave and pitch motions are investigated in time and frequency domains.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.113-116
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• 1998

This study should investigate to what extent the electric field of a vacuum interrupter might be influenced by the electric potential of floating arc shield. The electric potentials of floating shield and electric fields of a vacuum interrupter are analysed by a finite element method against variation of gap distances from 1mm to 12mm. The electric potentials of floating shield was increased with the gap distance, which is because the relative position of shield is closer to fixed contact so that the capacitance distribution inside interrupter is varied. The calculated results show that the maximum value of electric field of a vacuum interrupter with floating shield is nearly same to that without shield at shorter gap distance(below 5mm), however at larger gaps a significant increment of electric field is achieved in interrupter with shield companying with model without shield, which is due to the influence of charged floating shield.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권3호
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• pp.252-261
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• 2016

A spar-type floating substructure that is being widely used for offshore wind power generation is vulnerable to resonance in the heave direction because of its small water plane area. For this reason, the stable dynamic response of this floating structure should be ensured by accurately identifying the resonance characteristics. The purpose of this study is to analyze the characteristics of the combination resonance between the excitation frequency of a regular wave and natural frequencies of the floating substructure. First, the nonlinear equations of motion with two degrees of freedom are derived by assuming that the floating substructure is a rigid body, where the heaving motion and pitching motions are coupled. Moreover, to identify the characteristics of the combination resonance, the nonlinear term in the nonlinear equations is approximated up to the second order using the Taylor series expansion. Furthermore, the validity of the approximate model is confirmed through a comparison with the results of a numerical analysis which is made by applying the commercial software ANSYS AQWA to the full model. The result indicates that the combination resonance occurs at the frequencies of ${\omega}{\pm}{\omega}_5$ and $2{\omega}_{n5}$ between the excitation frequency (${\omega}$) of a regular wave and the natural frequency of the pitching motion (${\omega}_{n5}$) of the floating substructure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.614-622
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• 2011

In this study, the computational structural dynamic modeling of floating offshore wind turbine system is presented using efficient equivalent modeling technique. Structural dynamic behaviors of the offshore floating platform with 5MW wind turbine system have been analyzed using computational multi-body dynamics based on the finite element method. The considered platform configuration of the present offshore wind turbine model is the typical spar-buoy type. Equivalent stiffness and damping properties of the floating platform were extracted from the results of the baseline model. Dynamic responses for the floating wind turbine models are presented and compared to investigate its structural dynamic characteristics. It is important shown that the results of the present equivalent modeling technique show good and reasonable agreements with those by the fully coupled analysis considering complex floating body dynamics.

• 한국산업융합학회 논문집
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• 제17권4호
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• pp.227-233
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• 2014

Information presented in this study is intended to inform candidates as they prepare to design and structure the floatovoltaics solar power system. A developed floatovoltaics solar power generation results from the combination of PV plant technology and PV floating technology. This floating-based PV system is a new concept for PV development. The PV floating technology opens new opportunities to give value to unused areas so far while preserving valuable land for more adapted activities. Therefore the land-use conflicts are avoided and the environmental impact is minimized. Therefore the technology offers an interesting opportunity to regions facing on drought during summer time without any negative impact to the eco-system. This study describe the basic components of a floatovoltaics solar power system. A typical system consist of floating system and solar modules, a control device, rechargeable batteries, a load or device and the associated electrical connections. The floating system is specifically designed to keep all metallic components above water leaving only 100% recyclable, closed cell foam filled HDPE plastic floats in contact with the water. As the first case that can maximize the power generation efficiency of PV internationally, it is expected that this study will be utilized as a primary guide for future development of floating type PV system.