• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.32-36
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• 2014

A tangible floating display that can provide different perspective views without special glasses being introduced. The proposed system can display perspective floating images in the space in front of the system with the help of concave mirrors. In order to avoid wearing special equipment to interact and deliver the sense of touch, the proposed system adopted an ultrasound focusing technology. For providing an immersive experience to the viewers, the proposed system consists of a tangible floating display system and a multiple-view imaging system for generating three lenticular displays in front of the users.

• Structural Engineering and Mechanics
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• v.63 no.1
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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.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.37-44
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• 2013

This study is about the connector of the floating platform in order to ensure safety due to various climate changes. The purpose of this study is to recommend the connector model of floating platform based on concrete structures after reviewing the literatures related in establishing floating structure in case of various climate changes in domestic coast. This study introduces the concept generation, existing model, detailed design and evaluation including current and future development of the technologies of marina floating platform connector based on concrete structures. The results from the research show that the analysed connector design (Rigid Pontoon Connector) provides a highly efficient and practical solution to facilitate connection of stable floating platform.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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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.

• Journal of Ocean Engineering and Technology
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• v.26 no.2
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• pp.48-57
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• 2012

This paper deals with numerical analyses in the context of estimations of hydrodynamic motions and dynamic loads for a floating type offshore platform using some exclusive simulation code such as code for the simulation of a floating type of offshore crane based on multi-body dynamics, along with the commercial code AQWA. Verifications of numerical models are carried out by comparing the RAO results from the simulation code. In the verification analyses, hydrodynamic motions are examined in the frequency domain for the floating type offshore platform according to the mooring lines. Both the hydrodynamic motions and dynamic loads are estimated for floating type offshore platforms equipped with the catenary type and taut mooring lines. A review and comparison are carried out for the numerically estimated results. The structural safety of the connection parts in an offshore structure such as a floating type offshore platform is one of the most important design criteria in view of fatigue life. The dynamic loads in the connecting area between a floating type offshore platform and its mooring lines are estimated in detail according to variations in the mechanical properties of the mooring lines. The dynamic tension load on the mooring lines is also estimated.

• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.22-32
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• 2013

This paper presents the conceptual design procedure for the taut-leg mooring lines of a floating-type combined renewable energy platform. The basic configuration of the platform is determined based on an understanding of floating offshore plants. The main dimensions and mass distribution are determined based on a hydrostatic calculation. To identify the motion history of the floating platform and the tension history of the mooring lines, a hydrodynamic analysis is executed using Ansys.Aqwa. This helps in the selection of the best configuration for the mooring system such as the number of mooring lines, wire types, anchored positions, etc. In addition, the fatigue life of the mooring lines can be predicted from the tension history using the rain-flow cycle counting method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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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.

• Wind and Structures
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• v.22 no.5
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• pp.525-541
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• 2016

An offshore wind turbine supported by a spar buoy floating platform is the subject of this study on tower and rotor extreme loads. The platform, with a 120-meter draft and assumed to be sited in 320 meters of water, supports a 5 MW wind turbine. A baseline model for this turbine developed at the National Renewable Energy Laboratory (NREL) is employed in stochastic response simulations. The support platform, along with the mooring system consisting of three catenary lines, chosen for loads modeling, is based on the "Hywind" floating wind turbine concept. Our interest lies in gaining an understanding of the dynamic coupling between the support platform motion and the turbine loads. We first investigate short-term response statistics using stochastic simulation for a range of different environmental wind and wave conditions. From this study, we identify a few "controlling" environmental conditions for which long-term turbine load statistics and probability distributions are established.

• Journal of Ocean Engineering and Technology
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• v.29 no.3
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• pp.255-262
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• 2015

The present study developed a numerical simulation tool for the coupled dynamic analysis of multiple turbines on a single floater (or Multiple Unit Floating Offshore Wind Turbine (MUFOWT)) in the time domain, considering the multiple-turbine aero-blade-tower dynamics and control, mooring dynamics, and platform motions. The numerical tool developed in this study was designed based on and extended from the single-turbine analysis tool FAST to make it suitable for multiple turbines. For the hydrodynamic loadings of floating platform and mooring-line dynamics, the CHARM3D program developed by the authors was incorporated. Thus, the coupled dynamic behavior of a floating base with multiple turbines and mooring lines can be simulated in the time domain. To investigate the effect of asymmetric aerodynamic loading on the global performance and mooring line tensions of the MUFOWT, one turbine failure case with a fully feathered blade pitch angle was simulated and checked. The aerodynamic interference between adjacent turbines, including the wake effect, was not considered in this study to more clearly demonstrate the influence of the asymmetric aerodynamic loading on the MUFOWT. The analysis shows that the unbalanced aerodynamic loading from one turbine in MUFOWT may induce appreciable changes in the performance of the floating platform and mooring system.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.4
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• pp.179-191
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• 2016

As the demand for renewable energy has increased following the worldwide agreement to act against global climate change and disaster, large-scale floating offshore wind systems have become a more viable solution. However, the cost of the whole system is still too high for practical realization. To make the cost of a floating wind system be more economical, a new concept of tension leg platform (TLP) type ocean floating wind system has been developed. To verify the performance of a 5-MW TLP type ocean floating wind power system designed by the Korea Advanced Institute of Science and Technology, the FAST simulation developed by the National Renewable Energy Laboratory is used. Further, 1/50 scale model tests have been carried out in the ocean engineering tank of the Research Institute of Medium and Small Shipbuilding, Korea. This paper compares the simulation and ocean engineering tank test results on motion prediction and tension assessment of the TLP anchor.