• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.80-92
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• 1994

The dynamic response characteristics of a floating ocean city are examined for presenting the basic data for the design of huge offshore structures supported by a large number of floating bodies in waves. The numerical approach which is accurate in linear system is based on combination of a three dimensional source distribution method, wave interaction theory and the finite element method of using the space frame element. The hydrodynamic interactions among the floating bodies are taken into account in their exact form within the context of linear potential theory in the motion and structural analysis. The method is applicable to an arbitrary number of three dimensional bodies having any individual body geometries and geometrical arrangement with the restriction that the circumscribed, bottom-mounted. Imaginary vertical cylinder for each body does not contain any part of the other body. The validity of this procedure was verified by comparing with experimental results obtained in the literature.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.71-76
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• 2005

This paper describes basic structural design for the large floating crane barge of fixed undulation type. Structural analysis was performed separately after dividing the floating crane into two parts, The crane part was composed of jib boom, back stay and back tower and the barge part supported the crane part. The structural strength for jib boom structural members are in compliance with JIS B 8821 and scantling of all barge structural members are in compliance with the requirement of KR (Korean Register of Shipping) Steel Barges and Rules for Classification of Steel Ships. For the structural analysis of large floating crane, MSC/NASTRAN and MSC/PATRAN software were used.

• Tribology and Lubricants
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• v.19 no.6
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• pp.349-356
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• 2003

A damper floating ring seal with round hole pattern surfaces is suggested for better leakage control. The flat plate test of the round hole pattern surfaces has been performed to yield an empirical friction factor model. The exact predictions of the lock­up position of the damper floating ring, the leakage performance, and the rotordynamic coefficients of the seal are necessary to evaluate the rotordynamic performance of the turbo pump unit. The governing equations including the empirical friction factor model for round hole pattern surfaces are solved by the Fast Fourier Transform method. The lock­up position, leakage flow rate, and rotordynamic coefficients are evaluated according to the geometric parameters of the damper floating ring seal. Theoretical results show that the damper floating ring seals yield less leakage and better rotordynamic stability than the floating ring seal with a smooth surface.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.461-467
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• 2016

In order to install the floating transport type wind-turbine foundation, water pumping is used to sink the foundation. During this process, its mass and center of gravity, and buoyancy center become continuously changed so that the dynamic stability of the floating foundation become unstable. Dynamic stability analysis of the floating foundation is a complex problem since it should take into account not only the environmental wave, wind, and current loads but also its weight change effect simultaneously considering six-degree-of-freedom motion. In this study, advanced numerical method based on the coupled computational fluid dynamics (CFD) and multi-body dynamics (MBD) approach has been applied to the dynamic stability analysis of the floating foundation. The sloshing effect of foundation internal water is also considered and the floating dynamic characteristics are numerically investigated in detail.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.6
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• pp.373-382
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• 2013

The weight of floating offshore plant, such as an FPSO(Floating, Production, Storage, and Off-loading unit) and an offshore wind turbine, is important for estimating the amount of production material and for determining the production method. Furthermore, the weight is a factor which affects in the building cost and production time of the floating offshore plant. Although the importance of the weight has long been recognized, the weight has been roughly estimated by using the existing design and production data, and designer's experience. To solve this problem, a simplified model for the weight estimation of the floating offshore plant using the statistical method was proposed in this study. To do this, various data for estimating the weight of the floating offshore plant were collected through the literature survey, and then the correlation analysis and the multiple regression analysis were performed to generate the simplified model for the weight estimation. Finally, to examine the applicability of the developed model, it was applied to examples of the weight estimation of an FPSO topsides and an offshore wind turbine. As a result, it was shown that the developed model can be applied the weight estimation process of the floating offshore plant at the early design stage.

• Ocean Systems Engineering
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• v.3 no.1
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• pp.35-53
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• 2013

In this study, a hybrid floating structure with cylinder was introduced to reduce the hydrodynamic motions of the pontoon type. The hybrid floating structure is composed of cylinders and semi-opened side sections to penetrate the wave impact energy. In order to exactly investigate the hydrodynamic motions and structural behavior of the hybrid floating structure under the wave loadings, integrated analysis of hydrodynamic and structural behavior were carried out on the hybrid floating structure. Firstly, the hydrodynamic analyses were performed on the hybrid and pontoon models. Then, the wave-induced hydrodynamic pressures resulting from hydrodynamic analysis were directly mapped to the structural analysis model. And, finally, the structural analyses were carried out on the hybrid and pontoon models. As a result of this study, it was learned that the hybrid model of this study was showed to have more favorable hydrodynamic motions than the pontoon model. The surge motion was indicated even smaller motion at all over wave periods from 4.0 to 10.0 sec, and the heave and pitch motions indicated smaller motions beyond its wave period of 6.5 sec. However, the hybrid model was shown more unfavorable structural behavior than the pontoon model. High concentrated stress occurred at the bottom slab of the bow and stern part where the cylinder wall was connected to the bottom slab. Also, the hybrid model behaved with the elastic body motion due to weak stiffness of floating body and caused a large stress variation at the pure slab section between the cylinder walls. Hence, in order to overcome these problems, some alternatives which could be easily obtained from the simple modification of structural details were proposed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.275-289
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• 2022

New businesses such as marine leisure and floating construction have recently flourished on the coast. As a result, consideration is given to a floating structure appropriate for marine environments. In this study, we applied a damping plate to increase the stability of a hybrid floating structure that was expanded by vertical and horizontal stacking of mobile unit modules. In the numerical analysis using ANSYS AQWA, the behavioral characteristics of the floating structure were analyzed according to the length change of the damping plate. However, the wave forces acting on a floating structure are excessively calculated by the resonance of fluid surrounded by the structure in the numerical analysis using potential flow. Therefore, we used the damping zone option of the ANSYS AQWA in the frequency domain analysis.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.3
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• pp.421-431
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• 2023

Recently, the destructive power of typhoons is continuously increasing due to the influence of global warming. In a situation where the installation of floating wind turbines is increasing around the world, concerns about the huge loss and collapse of floating offshore wind turbines due to strong typhoons are deepening. Regarding to the safe operation of the floating offshore wind turbine, the development of a new type of disconnectable mooring system is required. A new fairlead chain stopper considered in this study is devised to more easily attach or detach the floating offshore wind turbine with mooring lines comparing to other disconnectable mooring apparatuses. In order to investigate the structural safety of the initial design of fairlead chain stopper that can be applied to MW-class floating type offshore wind turbine, scale-down structural models were produced using a 3-D printer and structural tests were performed on the models. For the structural tests of the scale-down models, tensile specimens of acrylonitrile butadiene styrene material that was used in the 3-D printing were prepared, and the material properties were evaluated by performing the tensile tests. The finite element analysis of fairlead chain stopper was performed by applying the material properties obtained from the tensile tests and the same load and boundary conditions as in the scale-down model structural tests. Through the finite element analysis, the structural weak parts on the fairlead chain stopper were reviewed. The structural model tests were performed considering the main load conditions of fairlead chain stopper, and the test results were compared to the finite element analysis. Through the results of this study, it was possible to experimentally verify the structural safety of the initial design of fairlead chain stopper. It is also judged that the study results can be usefully used to improve the structural strength of fairlead chain stopper in a detailed design stage.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.55-62
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• 2015

Floating structure such as tension leg platform, semi-submersible and spar are widely used in field of oil exploration and renewable energy system. All of these structures have the base cylinder support structure which have effective rule in overall dynamic of response. So the accurate and reliable modeling is needed for optimum design and understanding the physical background of these systems. The aim of this article is an analytical discussion on stochastic modeling of floating cylinder based support structure but an applicable one. Due to this a mathematical mass-damper-spring system of a floating cylinder of HAWAII WTG offshore wind as an applicable and innovative system is adopted to model a coupled degrees using random vibration in analytical way. A fully develop spectrum is adopted to solve the stochastic spectrum analytically by a proper approximation. Some acceptable assumption is adopted. The simplified but analytical and innovative hydrodynamic analysis of this study not only will help researcher to concentrate more physically on hydrodynamic analysis of floating structures but also can be useful for any quick, simplified and closed form analysis of a complicated problem in offshore engineering.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.407-416
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• 2023

Demand for leisure facilities such as mooring facilities for berthing leisure vessels and floating pensions based on floating bodies is increasing owing to the rapid growth of the population and related industries for marine leisure activities. Owing to its relatively light weight as a fluid, inclination is easily generated by waves and surcharges flowing to the coast, resulting in frequent safety accidents because of the low stability. As a solution to this problem, a motion reduction device for floating bodies is proposed in this study. The device (motion reduction device based on the air pressure dif erence) was attached to a floating body and the effect was analyzed by comparing the results with those of a floating body without motion reduction. The effect analysis was further analyzed using a computer analysis test, and the method for increasing the stability of the floating body was studied, and its the effect was verified. Based on the analysis of the test results, the stability of the floating body increased with a motion damping device is higher than that of the floating body without a motion reducing device as the wave momentum reduces, owing to the air pressure difference. Therefore it was concluded that the use of such a device for reducing motion a floating body is useful not only for non-powered ships but also for powered and semi-submersible ships, and further research should be conducted by applying it to various fields.