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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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
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Applicability of Investigation Modified Design Wave Model Considering Diffraction and Water Depth Effects
Kim, Kyu Han ; Han, Ha Na ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 349~356
DOI : 10.9765/KSCOE.2013.25.6.349
The purpose of this study is to review and overcome the limits of the existing design wave model applied to such waters as those located inside bays or near islands where the impact of wind influenced waves are more dominant, due to the nature of topographic isolation, than the influence of direct waves coming from the open sea. Although the existing model for an inside bay design wave is excellent for considering wind factors and very adaptable to topographically complicated areas compared to other models, it is difficult to show the wave diffractions and reflections caused by large scale structures or topographic features in the region. The study examined the various methods capable of taking into account wave diffraction, the angle of wave reflection, and changes in water depth. As a result of applying the modified design wave model to the target situation (inside bay or near island areas), it was found that the reliability of the design wave height around marine structures was improved, compared to the existing models. Therefore, it is fair to predict that the new model could provide more accurate design waves in the design of marine structures.
Characteristic Analysis of Reduced Motion due to the Shape of Floating Structure
Lee, Du Ho ; Jeong, Youn Ju ; You, Young Jun ; Park, Min Su ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 357~364
DOI : 10.9765/KSCOE.2013.25.6.357
In previous study, the hybrid floating structure composed of a pontoon and a semi-submersible was suggested to reduce the motions of floating structure. It was reported that the suggested hybrid floating structure could reduce the motions. However, the hybrid floating structure could not support enough buoyancy. In this study, the combination floating structure is newly suggested to resolve the problem. In order to adopt the shape of floating structures reducing the motions, the hydrodynamic analysis of various floating structures such as the pontoon, the hybrid and the combination of floating structure is carried out through hydrodynamic analysis program ANSYS AQWA. It is found that the combination floating structure is remarkably effective to reduce the motions compared to the other cases. Thus, the suggested combination floating structure may be a useful offshore structure for constructing a very large floating structure.
Statistical Characteristics of Hourly Tidal Levels around the Korean Peninsula
Ko, Dong Hui ; Jeong, Shin Taek ; Cho, Hongyeon ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 365~373
DOI : 10.9765/KSCOE.2013.25.6.365
Representative tidal gauging (TG) stations are selected to cover the tidal characteristics of the Korean peninsula coastal seas, and the statistical parameters of the data are analysed from the perspective of the probability distribution at that TG station. The shape of the distribution in the Incheon and Gunsan TG stations, which are tide-dominated areas, shows two clear modes at HWONT and LWONT in the distributions, and in the Mokpo station, shows an asymmetric double peak distribution. In contrast, the frequency distribution shape shows a smoothed flat peak in the Jeju, Yeosu and Busan TG stations, and a single peak in the Pohang and Sokcho TG stations. The emersion and submersion equations suggested as the 6-parameter Gaussian mixture models in this study are accurate, and well fitted to the observed tidal elevation data. The
parameters are highly correlated to the LWONT and HWONT, and the
parameters are also closely correlated to the mean tidal range. The
parameters coincide with the modes of the suggested probability distribution of the hourly tidal level data.
Sediment Particulate Motions Over a Ripple Under Different Wave Amplitude Conditions
Chang, Yeon S. ; Ahn, Kyungmo ; Hwang, Jin H. ; Park, Young-Gyu ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 374~385
DOI : 10.9765/KSCOE.2013.25.6.374
Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundary layer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated using Lagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing two different wave amplitudes while keeping other conditions such as wave period same. As expected, the amount of suspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flow intensity. However, it is also observed that the pattern of suspension may be different as well due to the only different condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the wave period is not coincident between the two cases because sediment suspension is strongly affected by the existence of turbulent eddies that are formed at different times over the ripple between the two cases as well. The role of these turbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it is also found the time of these eddies' formation may also dependent on the wave amplitude over rippled beds. Therefore, it has been proved that various flow as well as geometric conditions under waves has to be considered in order to have better understanding on the sediment suspension process over ripples. In addition, it is found that high turbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supports high suspension rate at these time steps. The results indicate that the relationship between the structure of flows and bedforms has to be carefully examined in studying sediment suspension at coastal regions.
Numerical Study on Propagation Characteristics of Tsunami Induced by Tokai, Tonankai and Nankai Massive Earthquakes
Kawasaki, Koji ; Suzuki, Kazuki ; Lee, Kwang-Ho ; Kim, Do-Sam ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 386~393
DOI : 10.9765/KSCOE.2013.25.6.386
After the 2011 Tohoku Earthquake, it has been pointed out that Tokai, Tonankai and Nankai massive earthquakes with a magnitude of 9.0 could strike the Pacific coasts in western Japan. This study aims at investigating numerically propagation characteristics of tsunami generated by a 9.0 magnitude Tokai, Tonankai and Nankai massive earthquakes on the Pacific coasts and three major bays in Japan, Tokyo Bay, Ise Bay and Osaka Bay. It was revealed from the numerical results that the tsunami heights on the Pacific coasts for M9.0 earthquake were about twice as much as those for M8.7 earthquake and the first tsunami arrival time was faster at some areas distant from the tsunami source. Moreover, high water level in the bays was recognized to continue for a long time because of the enclosed bays.
Analysis of the Wave Spectral Shape Parameters for the Definition of Swell Waves
Ahn, Kyungmo ; Chun, Hwusub ; Jeong, Weon Mu ; Park, Deungdae ; Kang, Tae-Soon ; Hong, Sung-Jin ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 394~404
DOI : 10.9765/KSCOE.2013.25.6.394
In the present study, the characteristics of spectral peakedness parameter
, bandwidth parameter
, and spectral width parameter
were analyzed as a first step to define the swell waves quantitatively. For the analysis, the joint probability density function of significant wave heights and peak periods were newly developed. The MCMC(Markov Chain Monte Carlo) simulations have been performed to generate the significant wave heights and peak periods from the developed probability density functions. Applying the simulated significant wave heights and peak periods to the theoretical wave spectrum models, the spectral shapes parameters were obtained and analyzed. Among the spectral shape parameters, only the spectral peakedness parameter
, is shown to be independent with the significant wave height and peak wave period. It also best represents the peakedness of the spectral shape, and henceforth
should be used to define the swell waves with a wave period. For the field verification of the results, wave data obtained from Hupo port and Ulleungdo were analyzed and results showed the same trend with the MCMC simulation results.
Sediment Transport Calculation Considering Cohesive Effects and Its Application to Wave-Induced Topographic Change
Cho, Yong Hwan ; Nakamura, Tomoaki ; Mizutani, Norimi ; Lee, Kwang-Ho ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 405~411
DOI : 10.9765/KSCOE.2013.25.6.405
A sediment transport calculation considering cohesive force is proposed to deal with the transport phenomena of cohesive sediment. In the proposed calculation, each sand particle is assumed to be surrounded by a thin layer of mud. The critical Shields parameter and bed-load sediment transport rate are modified to include the cohesive force acting on the sand particle. The proposed calculation is incorporated into a two-way coupled fluid-structure-sediment interaction model, and applied to wave-induced topographic change of artificial shallows. Numerical results show that an increase in the content ratio of the mud, cohesive resistance force per unit surface area and water content cause increases in the critical Shields parameter and decreases in the bed-load sediment transport rate, reducing the topographic change of the shallow without changing its trend. This suggests that mixing mud in the pores of the sand particles can reduce the topographic change of shallows.
Estimation of Seismic Fragility for Busan and Incheon Harbor Quay Walls
Kim, Young Jin ; Kim, Dong Hyawn ; Lee, Gee Nam ; Park, Woo Sun ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 412~421
DOI : 10.9765/KSCOE.2013.25.6.412
Nowadays, small and medium-sized earthquakes occur frequently in the west coast of Korea. The earthquake induced damages on the harbor structure such as quay wall possibly make a severe impact on national economy. Therefore, not only a seismic design for the structures but warning system for seismic damage right after the occurrence of earthquake should be developed. In this study, seismic fragility analysis was performed to be given to earthquake damage prediction system for quay wall structures in Busan and Incheon harbor. Four types of structures such as pier-type, caisson type, counterfort type, block-type were analyzed and fragility curves of functional performance level and collapse prevention level based on displacement criteria were found. Regression analyses by using the results of the two ports were done for possible use in other port structures.
Modelling of Wind Wave Pressure and Free-surface Elevation using System Identification
Cieslikiewicz, Witold ; Badur, Jordan ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 422~432
DOI : 10.9765/KSCOE.2013.25.6.422
A System Identification method to develop parametric models linking free surface elevation and wave pressure is presented and two models are built allowing for either wave pressure or free surface elevation simulation. Linear, time invariant model structures with static nonlinearities are assumed and solutions are sought in a form of autoregressive model with extra input (ARX). An arbitrary chosen free-surface elevation and wave pressure dataset is used for estimation of the models, which are subsequently verified against datasets with similar pressure gauge depth but different free-surface elevation spectra due to different meteorological conditions. It is shown that free-surface simulation using System Identification methods can perform better than traditional linear transfer function derived from linear wave theory (LTF), while wave pressure simulation quality using presented methods is generally similar to that obtained with corrected LTF.
An Overview of Marine Renewable Energy
Kim, Young C. ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 25, issue 6, 2013, Pages 433~438
DOI : 10.9765/KSCOE.2013.25.6.433
With the prospect of an increasing shortage of energy resources, there has been a growing interest in renewable alternative sources of energy. An increasing effort is being directed towards resolving the problems of extracting energy from the world's oceans, as they represent a vast potential source of renewable energy. This paper summarizes the extraction and conversion techniques of the ocean's energy resources, namely, energy derived from the ocean waves, tides, thermal gradients, and currents. For each energy extraction and conversion technique, case studies are discussed.