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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Korean Society of Coastal and Ocean Engineers
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Journal DOI :
Korean Society of Coastal and Ocean Engineers
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Volume & Issues
Volume 25, Issue 6 - Dec 2013
Volume 25, Issue 5 - Oct 2013
Volume 25, Issue 4 - Aug 2013
Volume 25, Issue 3 - Jun 2013
Volume 25, Issue 2 - Apr 2013
Volume 25, Issue 1 - Feb 2013
Selecting the target year
Buckling Behaviors of Bucket Foundation for Offshore Wind Tower
Lee, Gye Hee ; Tran, Duc Phu ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 123~127
DOI : 10.9765/KSCOE.2013.25.3.123
In this study, the buckling behaviors during the installation of a bucket foundation for an offshore wind turbine tower were investigated. The objective structure was modeled by using a commercial structural analysis program, and the buckling behavior of the model was estimated as Batdorf's parameter Z in the design code. The surrounding soil conditions and loading condition were applied to the verified analysis model. The effects of parameters such as the longitudinal stiffeners and driven depth were estimated for the buckling capacity. As a result, it was found that the longitudinal stiffeners could drastically increase the buckling capacity in a specific region. In addition, the buckling capacities increased linearly when considering the effect of the surrounding soil.
Numerical Simulation of Irregular Airflow in OWC Wave Generation System Considering Sea Water Exchange
Lee, Kwang Ho ; Park, Jung Hyun ; Cho, Sung ; Kim, Do Sam ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 128~137
DOI : 10.9765/KSCOE.2013.25.3.128
Due to the global warming and air pollution, interest in renewable energies has increased in recent years. In particular, the crisis of the depletion of fossil energy resources in the near future has accelerated the renewable energy technologies. Among the renewable energy resources, oceans covering almost three-fourths of earth's surface have an enormous amount of energy. For this reason, various approaches have been made to harness the tremendous energy potential. In order to achieve two purposes: to improve harbor water quality and to use wave energy, this study proposed a sea water exchange structure applying an Oscillating Water Column (OWC) wave generation system that utilizes the air flow velocity induced by the vertical motion of water column in the air chamber as a driving force of turbine. In particular, the airflow velocity in the air chamber was estimated from the time variations of water surface profile computed by using 3D-NIT model based on the 3-dimensional irregular numerical wave tank. The relationship of the frequency spectrums between the computed airflow velocities and the incident waves was analyzed. This study also discussed the characteristics of frequency spectrums in the air chamber according to the presence of the structure, wave deformations by the structure, and the power of the water and air flows were also investigated. It is found that the phase difference exists in the time series data of water level fluctuations and air flow in the air chamber and the air flow power is superior to the fluid flow power.
Development of a Stability Formula for Tetrapod by Using M5' Model Tree
Kim, Seung-Woo ; Suh, Kyung-Duck ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 138~146
DOI : 10.9765/KSCOE.2013.25.3.138
Tetrapod, one of the famous armor blocks for rubble mound breakwaters, has been widely used in the world. In order to evaluate the required weight of Tetrapod, many researchers have proposed various stability formulas. Since the stability formulas were proposed by curve-fitting the experimental data, some uncertainties are included in the formulas. The main uncertainties are associated with experimental data, derivation of the formula, and variability of the design variables. In this study, a new stability formula is developed by using M5' model tree, which reduces the uncertainty in the derivation of the formula. The index of agreement is used to evaluate the performance of the developed formula. The index of agreement for the new formula is higher by about 0.1 than the previous formula. The performance of the previous formula was not good when the predicted stability number is greater than about 3.0. However. the new formula is accurate regardless of the magnitude of stability number. As a result, the new formula performs better than the previous formula, while expressed in the form of a tree but still in an explicit form.
Wave Analysis and Spectrum Estimation for the Optimal Design of the Wave Energy Converter in the Hupo Coastal Sea
Kweon, Hyuck-Min ; Cho, Hongyeon ; Jeong, Weon-Mu ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 147~153
DOI : 10.9765/KSCOE.2013.25.3.147
There exist various types of the WEC (Wave Energy Converter), and among them, the point absorber is the most popularly investigated type. However, it is difficult to find examples of systematically measured data analysis for the design of the point absorber type of power buoy in the world. The study investigates the wave load acting on the point absorber type resonance power buoy wave energy extraction system proposed by Kweon et al. (2010). This study analyzes the time series spectra with respect to the three-year wave data (2002.05.01~2005.03.29) measured using the pressure type wave gage at the seaside of north breakwater of Hupo harbor located in the east coast of the Korean peninsula. From the analysis results, it could be deduced that monthly wave period and wave height variations were apparent and that monthly wave powers were unevenly distributed annually. The average wave steepness of the usual wave was 0.01, lower than that of the wind wave range of 0.02-0.04. The mode of the average wave period has the value of 5.31 sec, while mode of the wave height of the applicable period has the value of 0.29 m. The occurrence probability of the peak period is a bi-modal type, with a mode value between 4.47 sec and 6.78 sec. The design wave period can be selected from the above four values of 0.01, 5.31, 4.47, 6.78. About 95% of measured wave heights are below 1 m. Through this study, it was found that a resonance power buoy system is necessary in coastal areas with low wave energy and that the optimal design for overcoming the uneven monthly distribution of wave power is a major task in the development of a WEF (Wave Energy Farm). Finding it impossible to express the average spectrum of the usual wave in terms of the standard spectrum equation, this study proposes a new spectrum equation with three parameters, with which basic data for the prediction of the power production using wave power buoy and the fatigue analysis of the system can be given.
A Study on Tranquility by the Development of New Type Floating Breakwater
Lee, Hyun Jin ; Kim, Do Sam ; Shin, Moon Seup ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 154~164
DOI : 10.9765/KSCOE.2013.25.3.154
In this study, a new type floating breakwater was proposed to improve the capability of wave attenuation compared with the existing floating breakwater in Wonjun Port, which is located in Masan City, Korea. In order to develop the optimal design, many different configurations considering the shape and location of vertical barrier and horizontal plate were examined based on the shape of existing floating breakwaters in Wonjun and Tongyeong Port. The analytical and numerical results of the new type floating breakwater showed better performance in long-period wave attenuation than the existing floating breakwater in Wonjun. Therefore, the new type floating breakwater can improve harbor tranquility in Wonjun Port.
Decomposition of Tidal Residual Data Using a Wavelet Method and Characteristic Analysis of Their Short-period Components
Kang, Ju Whan ; Kim, Yang-Seon ; Cho, Hongyeon ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 165~171
DOI : 10.9765/KSCOE.2013.25.3.165
The fact that tidal residuals are detected greatly at the tide-dominated region implies that tide component has still remained in the tidal residual. Auto-correlation function analysis also show that the auto-correlation coefficients are conspicuous near tidal periods at the Western Coast. A wavelet method was used to analyze characteristics of the short period or tide-relevant residuals. Considering the results that tidal period is prominent at the tide-dominated region, that seasonal variation is trivial at the short periods, and that shallow tidal period is conspicuous at Mokpo, the short period can be considered to be correlated with tide modulated surge. The result also shows short period components stem mainly from tide-forecasting error and tide-surge interaction. Thus tide modulated surge must be distinguished from meteorological surge.
Study on the Basic Design Method of Submerged Breakwater Composed of Double-Layer Permeable Blocks
Lee, Dal Soo ; Oh, Sang-Ho ; Park, Yi-Dong ; Jeong, Weon-Mu ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 3, 2013, Pages 172~180
DOI : 10.9765/KSCOE.2013.25.3.172
The focus of this study is to provide a method for determining the dimension of a submerged breakwater satisfying the target transmission performance or predicting the transmission coefficient of a given structure. This method was developed based on data analysis of the physical experiment that was carried out by using the submerged breakwater composed of double-layer permeable blocks. Two different armor blocks of Tetrapod and Triangular Pyramid Block were used in the experiment. The parameter
was introduced in the analysis of the measurement data. By using the linear regression line deduced from the analysis of the experimental data, it was possible to readily predict the wave transmission coefficient irrespective different water depths at the crest of the submerged breakwater, under the condition of significant decrease in transmitted wave height due to the submerged breakwater. This method can be effectively utilized for estimating the necessary number of blocks used for the submerged breakwater as well as comparing the transmission characteristics of the submerged breakwater according to use of different armor blocks.