• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.819-831
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• 2020

Wind load is one of the major design loads for the hull and mooring of offshore floating structures, especially due to much larger windage area above water than under water. By virtue of extreme design philosophy, fully turbulent flow assumption can be justified and the hydrodynamic characteristics of the flow remain almost constant which implies the wind load is less sensitive to the Reynolds number around the design wind speed than wind profile. In the perspective of meteorology, wind profile used for wind load estimation is a part of Atmospheric Boundary Layer (ABL), especially maritime ABL (MBL) and have been studied how to implement the profile without losing turbulence properties numerically by several researchers. In this study, the MBL is implemented using an open source CFD toolkit, OpenFOAM and extended to unstable ABL as well as neutral ABL referred to as NPD profile. The homogeneity of the wind profile along wind direction is examined, especially with NPD profile. The NPD profile was applied to a semi-submersible rig and estimated wind load was compared with the results from wind tunnel test.

• Wind and Structures
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• 제32권4호
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• pp.321-340
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• 2021

In 2019, 5.6% of the total energy produced worldwide came from wind. Offshore wind generation is still a small portion of the total wind generation, yet its growth is exponential. Higher availability of sites, larger producibility and potentially lower environmental impacts make offshore wind generation attractive. On the other hand, as the water depth increases, fixed foundations are no more viable, and the new frontier is that of floating foundations. This paper brings an overview of why and how offshore wind energy should move deep water; it contains material from the Keynote Lecture given by the first author at the ACEM20/Structures20 Conference, held in Seoul in August 2020. The paper is organized into four sections: the first giving general concepts about wind generation especially offshore, the second and the third considering economic and technical aspects, respectively, of offshore deep-water wind generation, in the fourth, some challenges of floating offshore wind generation are presented and some conclusions are drawn.

• 한국해양공학회지
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• 제5권2호
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• pp.16-30
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• 1991

A numerical procedure is described for predicting the dynamic responses of combined systems of floating breakwaters and huge offshore structures supported by a large numer of the floating bodies in waves. The hydrodynamic interactins among tatal floating bodies are taken into account in their exact form within the context of linear potential theory. Wave control effects are discussed with both hydrodynamic interactions and hydrodynamic-structure interaction effects. The method presented is applicalbe to combined systems of floating breakwaters and huge structures for ocean space utilization for which a number of practical uses are seen in the future.

• 한국해양공학회지
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• 제5권2호
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• pp.156-156
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• 1991

A numerical procedure is described for predicting the dynamic responses of combined systems of floating breakwaters and huge offshore structures supported by a large numer of the floating bodies in waves. The hydrodynamic interactins among tatal floating bodies are taken into account in their exact form within the context of linear potential theory. Wave control effects are discussed with both hydrodynamic interactions and hydrodynamic-structure interaction effects. The method presented is applicalbe to combined systems of floating breakwaters and huge structures for ocean space utilization for which a number of practical uses are seen in the future.

• 한국지진공학회논문집
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• 제19권4호
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• pp.145-159
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• 2015

A seismic response analysis method for three-dimensional floating offshore structures due to seaquakes is developed. The hydrodynamic pressure exerted on the structure is calculated taking into account the compressibility of the sea water, the fluid-structure interaction, the energy absorption by the seabed, and the energy radiation into infinity. To validate developed method, the hydrodynamic pressure induced by the vibration of a floating massless rigid circular disk is calculated and compared with an exact analytical solution. The developed method is applied to seismic analysis of a support structure for a floating offshore wind turbine subjected to the hydrodynamic pressures induced from a seaquake. Analysis results show that earthquake response of a floating offshore structure can be greatly influenced by the compressibility of fluid, the depth (natural frequencies) of the fluid domain, and the energy absorption capacity of the seabed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.161-165
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• 2001

Recently, mega-float offshore structure is studied as one of the effective utilization of the ocean space. And mega-float structure are now being considered for various applications such as floating airports, offshore cities and so on. This mega-float structure is relatively flexible compared with real floating structures like large ships. when we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compared with horizontal. The analysis of the dynamic response as it receives regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. In order to know the characteristics of the dynamic response of the mega-float structures, effects of wavelength, water depth, and wave direction on dynamic response of the floating structure are studied by use of numerical calculation.

• 대한자원환경지질학회:학술대회논문집
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• 대한자원환경지질학회 2001년도 춘계 공동학술발표회 논문집
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• pp.66-70
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• 2001

Recently, mega-float offshore structure is studied as one of the effective utilization of the ocean space. And mega-structure are now being considered for various applications such as floating airports, offshore cities and so on. This mega-float structure is relatively flexible compared with real floating structures like large ships. when we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compared with horizontal. The analysis of the dynamic response as it receives regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. In order to know the characteristics of the dynamic response of the mega-float structures, effects of wavelength, water depth, and wave direction on dynamic response of the floating structure are studied by use of numerical calculation.

• Journal of Ship and Ocean Technology
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• 제6권3호
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• pp.13-25
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• 2002

In this paper, the motion responses with hydrodynamic interaction effect between two off-shore floating structures in various heading waves are studied by using a linearized three-dimensional potential theory. Numerical calculations using three-dimensional pulsating source distribution techniques have been carried out for twelve coupled linear motion responses and relative motions of the barge and the ship in oblique waves. The computational results give a good correlation with the experimental results and also with other numerical results. As a result, the present computational tool can be used effectively to predict the motion responses of multiple offshore floating structures in waves.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.973-979
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• 2002

Recently, floating offshore structure is studied as one of the effective utilization of the ocean space. And floating structure are now being considered for various applications such as floating airports, offshore cities and so on. The analysis of the dynamic response as it receives regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. In order to know the characteristics of the dynamic response of the floating structures, effects of wavelength, water depth, and wave direction on dynamic response of the floating structure are studied by use of numerical calculation.

• Wind and Structures
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• 제24권4호
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• pp.333-350
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• 2017

Differing from the fixed-type, the dynamic motion of floating-type offshore wind turbines is very sensitive to wind and wave excitations. Thus, the sensing and monitoring of its motion is important to evaluate the dynamic responses to the external excitation. In this context, a monitoring system for sensing and processing the wind-induced dynamic motion of spar-type floating offshore wind turbine is developed in this study. It is developed by integrating a 1/00 scale model of 2.5MW spar-type floating offshore wind turbine, water basin equipped with the wind generator, sensing and data acquisition systems, real-time CompactRIO controller and monitoring program. The scale model with the upper rotatable blades is installed within the basin by means of three mooring lines, and its translational and rotational motions are detected by 3-axis inclinometer and accelerometers and gyroscope. The detected motion signals are processed using a real-time controller CompactRIO to calculate the acceleration and tilting angle of nacelle and the attitude of floating platform. The developed monitoring system is demonstrated and validated by measuring and evaluating the time histories and trajectories of nacelle and platform motions for three different wind velocities and for eight different fairlead positions.