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Kyong Hwan Kim

Bio: Kyong Hwan Kim is an academic researcher from Korean Ocean Research and Development Institute. The author has contributed to research in topics: Marine energy & Potential flow. The author has an hindex of 3, co-authored 5 publications receiving 32 citations.

Papers
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Journal ArticleDOI
TL;DR: The OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters, is summarized, with a focus on investigating the impact of different levels of nonlinearities in the numerical models.
Abstract: The International Energy Agency Technology Collaboration Programme for Ocean Energy Systems (OES) initiated the OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters (WECs). The long-term goal is to assess the accuracy of and establish confidence in the use of numerical models used in design as well as power performance assessment of WECs. To establish this confidence, the authors used different existing computational modelling tools to simulate given tasks to identify uncertainties related to simulation methodologies: (i) linear potential flow methods; (ii) weakly nonlinear Froude–Krylov methods; and (iii) fully nonlinear methods (fully nonlinear potential flow and Navier–Stokes models). This article summarizes the code-to-code task and code-to-experiment task that have been performed so far in this project, with a focus on investigating the impact of different levels of nonlinearities in the numerical models. Two different WECs were studied and simulated. The first was a heaving semi-submerged sphere, where free-decay tests and both regular and irregular wave cases were investigated in a code-to-code comparison. The second case was a heaving float corresponding to a physical model tested in a wave tank. We considered radiation, diffraction, and regular wave cases and compared quantities, such as the WEC motion, power output and hydrodynamic loading.

29 citations

Journal ArticleDOI
02 Mar 2021-Energies
TL;DR: In this article, the authors present results for a breakwater-mounted Oscillating Water Column (OWC) device at scale 1:4 relative to a full-scale installation in a water depth of 12.8 m. The power-extracting air turbine is modeled by an orifice plate of 1-2% of the internal chamber surface area.
Abstract: This paper reports on an ongoing international effort to establish guidelines for numerical modeling of wave energy converters, initiated by the International Energy Agency Technology Collaboration Program for Ocean Energy Systems. Initial results for point absorbers were presented in previous work, and here we present results for a breakwater-mounted Oscillating Water Column (OWC) device. The experimental model is at scale 1:4 relative to a full-scale installation in a water depth of 12.8 m. The power-extracting air turbine is modeled by an orifice plate of 1–2% of the internal chamber surface area. Measurements of chamber surface elevation, air flow through the orifice, and pressure difference across the orifice are compared with numerical calculations using both weakly-nonlinear potential flow theory and computational fluid dynamics. Both compressible- and incompressible-flow models are considered, and the effects of air compressibility are found to have a significant influence on the motion of the internal chamber surface. Recommendations are made for reducing uncertainties in future experimental campaigns, which are critical to enable firm conclusions to be drawn about the relative accuracy of the numerical models. It is well-known that boundary element method solutions of the linear potential flow problem (e.g., WAMIT) are singular at infinite frequency when panels are placed directly on the free surface. This is problematic for time-domain solutions where the value of the added mass matrix at infinite frequency is critical, especially for OWC chambers, which are modeled by zero-mass elements on the free surface. A straightforward rational procedure is described to replace ad-hoc solutions to this problem that have been proposed in the literature.

11 citations

Journal ArticleDOI
25 Feb 2016
TL;DR: In this paper, the dynamic performance of a large floating wave-offshore hybrid power generation platform in extreme conditions was evaluated by measuring motion responses in regular waves and complicated environmental conditions including wave, wind, and current.
Abstract: The present study experimentally considers dynamic performance of large floating wave-offshore hybrid power generation platform in extreme conditions. In order to evaluate the motion performance of the large floating hybrid power generation platform, 1/50 scaled model was manufactured. A mooring line was also manufactured, and free-decay and static pull-out tests were carried out to check the mooring model. A mooring line table was introduced to satisfy the water depth, and environmental conditions were checked. Motion responses in regular waves were measured and complicated environmental conditions including wave, wind, and current were applied to see the dynamic performance in extreme/survival conditions. Maximum motion and acceleration were judged following the design criteria, and maximum offset and mooring tension were also checked based on the rule. The characteristics of hybrid power generation platform are discussed based on these data.

7 citations

Patent
16 Nov 2017
TL;DR: In this article, a platform for a semi-submersible floating marine structure is arranged on the ocean surface and comprises: a main body portion having a structure in which a plurality of pontoons are coupled in the shape of polygons; and protruding member-connecting parts, which extend from each corner part of the main body part, for connecting protruding members protruding out from the main part portion with the other.
Abstract: A platform for a semi-submersible floating marine structure, according to one embodiment of the present invention, is arranged on the ocean surface and comprises: a main body portion having a structure in which a plurality of pontoons are coupled in the shape of a plurality of polygons; and protruding member-connecting parts, which extend from each corner part of the main body portion, for connecting protruding members protruding out from the main body portion with the main body portion. On a pontoon at the perimeter of the platform for the floating marine structure, a mooring line coupling portion for coupling a mooring line is installed, wherein the protruding members are for installing a tower and further comprise a protruding member-reinforcement part for supporting the protruding members.

Cited by
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Journal ArticleDOI
TL;DR: A critical overview of the state-of-the-art in wave energy device geometry optimisation is provided, comparing and contrasting various optimisation approaches, and attempting to detail the current limitations preventing further progress, and convergence, in the development of optimal wave energy technology.

50 citations

Book ChapterDOI
14 Dec 2015

41 citations

Journal ArticleDOI
TL;DR: In general, the NS solvers appear to predict the behaviour of the structures better than the linearised methods but there is considerable variation in the results (even between similar methods).
Abstract: Results from the CCP-WSI Blind Test Series 3 are presented. Participants, with numerical methods, ranging from low-fidelity linear models to high-fidelity Navier–Stokes (NS) solvers, simulate the interaction between focused waves and floatingstructures without prior access to the physical data. The waves are crest-focused NewWaves with various crest heights.Two structures are considered: a hemispherical-bottomed buoy and a truncated cylinder with a moon-pool; both are taut-moored with one linear spring mooring. To assess the predictive capability of each method, numerical results for heave,surge, pitch, and mooring load are compared against corresponding physical data. In general, the NS solvers appear topredict the behaviour of the structures better than the linearised methods, but there is considerable variation in the results(even between similar methods). Recommendations are made for future comparative studies and development of numericalmodelling standards.

39 citations

Journal ArticleDOI
TL;DR: This paper proposes a discussion and validation of three mooring-line models: one quasi-static approach (developed in-house) and two dynamic lumped-mass approaches (the open source MoorDyn and the commercial OrcaFlex) and a case study is a 1:32-scale prototype of a floating oscillating water column WEC tested in a wave tank.
Abstract: The mooring system of floating wave energy converters (WECs) has a crucial impact on power generation efficiency, cost of delivered energy, proper operation, reliability and survivability. An effective design, addressing such competing objectives, requires appropriate mathematical models to predict mooring loads and dynamic response. However, conversely to traditional offshore engineering applications, experience in modelling mooring systems for WECs is limited, due to their unique requirement of maximising the motion while minimising loads and costs. Even though modelling approaches and software are available for this application, guidelines and critical comparison are still scarce. This paper proposes a discussion and validation of three mooring-line models: one quasi-static approach (developed in-house) and two dynamic lumped-mass approaches (the open source MoorDyn and the commercial OrcaFlex). The case study is a 1:32-scale prototype of a floating oscillating water column WEC tested in a wave tank, with three mooring lines, each one comprising of a riser and a clump weight. Validation, performed by imposing fairlead displacements and comparing resulting tensions, shows good agreement. The small scale may induce numerical instabilities and uncertainties in the parameter estimation. Finally, likely due to internal resonance of this particular mooring system, high-frequency content in the mooring tension is found, albeit absent in the kinematics of the floater.

34 citations

Journal ArticleDOI
TL;DR: In this article, a model test was carried out for various sea states, including rotating rotor effect with wind in the Ocean Engineering Wide Tank, University Of Ulsan (UOU).

32 citations