• Journal of Ocean Engineering and Technology
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• v.17 no.6
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• pp.1-6
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• 2003

Wave energy dissipation and energy transfer between wave components, during the directional wave breakings, are investigated. Directional incipient and plunging breakers were generated by focusing the multi-frequency and multi-directional wave components at a designed location, based on a constant wave amplitude and a constant wave steepness frequency spectrum. The time series of surface wave elevation was measured at 9 different locations around the wave focusing point, using a wave gauge array. In order to examine the variation of the directional spreading function, the horizontal velocity of fluid motion was also measured. By comparing energy spectrums, before and after the breaking, the characteristics of energy dissipation and energy transfer, caused by wave breaking, are investigated. Their dependencies on directionality, as well as frequency, are analyzed. The breakings significantly dissipate wave energy, through energy transfer, in the upper region of the peak-frequency band, while enhancing wave energy in the low-frequency band.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.2
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• pp.94-102
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• 2013

In this study, numerical modeling was performed to investigate influence of the apron shape on the discharge performance of the sluice for tidal power plant. The numerical modeling was carried out for comparison of the difference in the discharge coefficient when the apron width, slope, and the length of the horizontal section were different, without considering change in the shape of the sluice caisson itself. The modeling result showed that significant discrepancy in terms of the overall discharge performance appeared according to the apron geometry. In order to achieve maximum discharge performance of the sluice caisson, it is desirable to make the design by putting a space equivalent to the width of the sluice caisson on its both sides, by making the apron slope be 1:5, and by keeping length of the horizontal section to be 50 m that is corresponding to the streamwise length of the sluice caisson.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.3
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• pp.141-147
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• 2006

A newly designed floating breakwater made of Polyethylene with considering the introduction of new material for being harmony with environment and stability of the floater is developed for a marine ranching. In this study, the new concept in which incident wave dissipates its energy due to the vortex shedding by passing through the pipes and sheets is selected for wave breaking mechanism. Model experiment in order to te st its capability is performed for the regular and irregular waves in ocean engineering basin. Good capability to break the incident wave within the 6 seconds of period and 1 m of height is shown. Breaking efficiency for long period wave is not so good in regular and irregular wave. The results of this study will contribute to the design and construction of the floating breakwater.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.178-186
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• 2021

The wave power extraction by multiple Wave Energy Converters (WECs) deployed in a Y-shaped Water Channel Resonator (WCR) has been investigated. A WCR consists of a long water channel, and a V-shaped wave guider installed at the entrance of a water channel. If the period of the incident waves coincides with the natural periods of the fluid in a WCR, resonance occurs, as a result, the internal fluid in a WCR is greatly amplified. To estimate the wave power by multiple WECs placed at the antinodal points in a WCR, the heave motion response, time-averaged power, and capture width ratio were calculated for several design parameters. Also, the systematic model tests were conducted in a 2D wave tank. The numerical results are in good agreement with the experimental data. It was verified that a WCR helps the WECs to produce electricity more effectively by amplifying the wave energy in a WCR.

• New & Renewable Energy
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• v.20 no.2
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• pp.2-16
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• 2024

Various loads induced by marine environmental conditions, such as waves, currents, and wind, are crucial for the operation and viability of offshore wind power (OWP) systems. In particular, waves have a significant impact on the stress and fatigue load of offshore structures, and highly reliable design parameters should be derived through extreme value analysis (EVA) techniques. In this study, extreme wave analyses were conducted with various Weibull distribution models to determine the reliable design parameters of an OWP system suitable for the Ulsan area. Forty-three years of long-term hindcast data generated by a numerical wave model were adopted as the analyses data, and the least-squares method was used to estimate the parameters of the distribution function for EVA. The inverse first-order reliability method was employed as the EVA technique. The obtained results were compared among themselves under the assumption that the marginal probability distributions were 2p, 3p, and exponentiated Weibull distributions.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.8
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• pp.704-709
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• 2016

Wave energy generation systems can be divided into oscillating water chamber type, over topping device type and wave activating body type. The wave activating body type converts wave energy to kinetic energy, and the power generation amount increases as the motion of an activating body increases. In this paper, the wave energy convertor consists of a main body, which has an H-shape, and the activating body. These are connected by a bar-type bridge. By the incident wave, when the activating body moves with vertical motion this motion is consequently converted into rotational motion. The twisting moment and angular velocity at a shaft of convertor are calculated according to various conditions of the incident wave and the shape of the activating body. This can be used as a basic idea for determining the design of wave activating body type convertor.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.6
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• pp.419-427
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• 2015

Recently Energy Saving Device has been developed actively due to the regulation of the EEDI. This Energy Saving Device which is newly developed is integrated duct and stator. This paper verified performance of the Energy Saving Device through CFD. The experimentation to find the best pitch angle of each blade of the stator designed has been conducted. The angle of incidence of the duct has been obtained through the measurement of the wake. The experimentation has been carried out with and without Energy Saving Device. The efficiency increase was through these two experiments.

• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.3
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• pp.22-35
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• 2011

Incheon Bay has a suitable condition for tidal power generation due to the high tidal range by topographical effect. Therefore a study on the technology development for tidal energy utilization has been promoted since 2006. It is needed to deduce optimal alternatives to determine the suitable location of facilities for tidal power generation and to reduce the environmental damage from development. In order to carry out efficiently this mission, spatial information system is essential to manage and use various spacial elements related to the development and conservation. In this study, for the development of tidal energy, spatial data could be defined as three kinds of dataset. Fundamental dataset is defined as spatial data such as tide, tidal current, wave, erosion and sedimentation. Framework dataset is composed of topographical map, facility map and bathymetry. The reference dataset is composed of marine ecology and environment having the characteristics of thematic map. This study is mainly aimed at establishing methodology of conceptual spatial data modeling classifying as essential data model and optional data model through the definition of the components of spatial data.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.3
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• pp.173-180
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• 2007

Oscillating wave amplitude in a bottom-mounted OWC chamber designed for wave energy converter is investigated by applying characteristic wave conditions in Korean coastal water. The effects of shape parameters of OWC chamber in a view of wave energy absorbing capability are analyzed. Both experimental and numerical approaches are adopted and their results are compared to optimize the shape parameters which can result in a maximum power production under given wave distribution. The experiment was carried out in a wave flume under 2-D assumption of OWC chamber. The numerical scheme employed a hybrid Green integral equation which adopts the Rankine Green function inside chamber to take account of fluctuating air pressure, while it uses the Kelvin Green function in outer domain. Air duct diameter, chamber width, and submerged depths of front skirt and back wall of chamber changes the magnitude and peak frequency of wave absorption significantly.

• Journal of Digital Convergence
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• v.21 no.2
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• pp.1-7
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• 2023

This study examines the policy direction for energy self-reliant islands using marine energy. In other words, it was suggested that the environmental characteristics of the ocean should be considered by conducting a strategic marine environmental impact assessment when establishing an energy-independent island project plan. It was also suggested to proceed with preemptive site selection. In particular, it was emphasized that continuous monitoring of the marine environment should be carried out during the construction and operation of the marine energy development project. In addition, I emphasized the need to seek ways to expand marine environmental impact data and to actively participate and support the residents of the island, which is important in promoting self-reliant islands using ocean energy. This can be said to have a high probability of success when the government-led smart grid project group and KEPCO collaborate with each other. The results of the study analyzed through literature review are as follows. First, active participation and support for initiatives led by residents are needed. second,. KEPCO must collaborate with specialized public institutions such as the Smart Grid Project Group. Third, a strategic marine environment impact assessment should be introduced. Fourth, continuous marine environmental impact investigations should be conducted.