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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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Korean Society of Coastal and Ocean Engineers
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Volume & Issues
Volume 24, Issue 6 - Dec 2012
Volume 24, Issue 5 - Oct 2012
Volume 24, Issue 4 - Aug 2012
Volume 24, Issue 3 - Jun 2012
Volume 24, Issue 2 - Apr 2012
Volume 24, Issue 1 - Feb 2012
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A Study on Seawater Flow Characteristics inside the Shrouds used in Tidal Current Generation Systems for Various Geometric Angles under Constant Tidal Current Velocity
Kim, Jong-Won ; Lee, Sang-Ho ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 77~83
DOI : 10.9765/KSCOE.2012.24.2.077
Numerical analyses through Computational Fluid Dynamics have been performed to investigate the seawater flow field characteristics for various shrouds used in horizontal axis tidal current turbine systems. Seawater flow characteristics are largely influenced under constant tidal current velocity by the shroud geometry and there is considerable difference in fluid velocity distributions around the shrouds. Especially the location and magnitude of maximum seawater flow velocity directly affect turbine performance for power generation. For the cylinder-diffuser type shroud system whose cylinder and diffuser parts have the same length accelerated flow region is formed in the overall cylinder part while maximum velocity in the nozzle-diffuser type whose nozzle and diffuser parts have the same length with symmetry, locally appears near the minimum sectional area. In case of cylinder-diffuser type shroud fluid velocity increases rather high compared with current velocity. And fluid velocity at the centerline gradually increases from the entrance, and then decreases rapidly after reaching a peak close to the middle of the cylinder part unlike the nozzle-diffuser while there is not much variation near the rear of the shroud. These results of the seawater flow characteristics with various shroud geometries can be applied to optimal design for the development of efficient tidal current power generation systems.
Treatment of Inclined Boundaries in a Finite Element Model for the Mild-Slope Equation
Jung, Tae-Hwa ; Ryu, Yong-Uk ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 84~88
DOI : 10.9765/KSCOE.2012.24.2.084
A numerical skill for effective treatment of inclined boundaries in a finite element method is introduced. A finite element method has been frequently used to simulate hydraulic phenomena in a coastal zone since it can be applied to irregular and complex geometry. In case elliptic partial equations are governing equations for a finite element model, however, there is a difficulty in treating boundary conditions properly for cases in which boundaries are vertically inclined. In this study, a method to treat such inclined boundaries using Bessel functions for a finite element method is introduced and compared with analytical solutions.
Analysis on Response Characteristics of a Flexible Net Sheet in Waves
Cho, Il-Hyoung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 89~96
DOI : 10.9765/KSCOE.2012.24.2.089
Based on the hydroelastic theory and the matched eigenfunction expansion method(MEEM), the dynamic behavior of the porous flexible net sheet and wave forces have been investigated in monochromatic waves. The net sheet is installed vertically with the submergence depth. Top end of a net sheet is fixed and its lower end is attached by a clump weight. It is assumed that the initial tension is sufficiently large so that the effects of dynamictension variation can be neglected. The boundary condition on the porous flexible net sheet is derived based on Darcy`s fine-pore model and body boundary condition. The developed analytic model can be extended to the impermeable/permeable vertical plate and the impermeable flexible membrane. The analytical model was used to study the influence of design parameters(wave characteristics, porosity, submergence depth, initial tension) on the response characteristics and wave load of the net sheet.
Model Trajectory Simulation for the Behavior of the Namgang Dam Water in the Kangjin Bay, South Sea, Korea
Jung, Kwang-Young ; Ro, Young-Jae ; Kim, Baek-Jin ; Park, Kwang-Soon ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 97~108
DOI : 10.9765/KSCOE.2012.24.2.097
A Lagrangian particle tracking model coupled with the ECOM3D were used to study on the behavior of fresh water released from the Namgang Dam in terms of residence time in Kangjin Bay, South Sea, Korea. Model was calibrated until skill cores for elevation, velocity, temperature and salinity are satisfied over 85%. In the numerical simulation, particles were released in 1 hour time interval from the northern boundary. The different patterns of particle trajectory are identified under the varying dynamics from tidal to density-driven current. The average residence time of total particles are approximately 65.9 hours in the entire Kangjin Bay. The average residence time were increased from 55~65 to 70~80 hours during maximum discharge period. Discharge rate of fresh water and average residence time in the Kangjin Bay is high correlated with correlation coefficient over 0.81.
Characteristics of Waves around the Sea near Busan New Port Based on Continuous Long-term Observations during Recent 10 years
Jeong, Weon-Mu ; Oh, Sang-Ho ; Baek, Won-Dae ; Chae, Jang-Won ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 109~119
DOI : 10.9765/KSCOE.2012.24.2.109
Long-term wave observation was carried out near Busan New Port and the major wave characteristics were analyzed. At Busan New Port, waves from south direction were predominant throughout the year, while waves from the west, developed at the north sea of Geoje island, appeared almost the same frequency in winter season, showing apparent seasonal variation. During the observation period, the significant wave height was mostly less than 1 m, but it reached its maximum of 8.0 m when typhoon Maemi passed on September 2003. Also, the seasonal variation was hardly observed except July. In contrast, seasonal variation was apparent for the significant wave period, whose peak ranges 4~5 s in summer whereas about 3 s in winter. The largest significant wave period was 15.56 s, observed on June 2003. Meanwhile, the annual variation was negligible for mean wave direction as well as significant wave height and period. Further analysis of the wave data acquired for 5 years at 4.5 km south, in the south sea of Daejuk island, confirmed high correlation between the two observation points in summer and vice versa in winter.
Analysis of the Variation Pattern of the Wave Climate in the Sokcho Coastal Zone
Cho, Hong-Yeon ; Jeong, Weon-Mu ; Baek, Won-Dae ; Kim, Sang-Ik ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 120~127
DOI : 10.9765/KSCOE.2012.24.2.120
Exploratory data analysis was carried out by using the long-term wave climate data in Sokcho coastal zone. The main features found in this study are as follows. The coefficient of variations on the wave height and period are about 0.11 and 0.02, respectively. It also shows that the annual components of the wave height and period are dominant and their amplitudes are 0.24 m and 0.56 seconds, respectively. The amount of intra-annual variation range is about two times greater than that of the inter-annual variation range. The distribution shapes of the wave data are very similar to the log-normal and GEV(generalized extreme value) functions. However, the goodness-of-fit tests based on the KS test show as "rejected" for all suggested density functions. Then, the structure of the timeseries wave height data is roughly estimated as AR(3) model. Based on the wave duration results, it is clearly shown that the continuous and maximum duration is decreased as a power function shape and the total duration is exponentially decreased. Meanwhile, the environment of the Sokcho coastal zone is classified as a wave-dominated environment.
Parameters Analysis for Influence on the Local Scour around a Pipeline Exposed Waves and Currents
Kim, Kyoung-Ho ; Oh, Hyoun-Sik ; Kim, Heung-Guk ; Son, Kwang-Sik ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 128~137
DOI : 10.9765/KSCOE.2012.24.2.128
This paper deals with the local scour around a pipeline exposed to combined waves and current in the shallow water zone. To investigate the characteristics of the scour around a pipeline on the sea bed, experiments were performed according to the various pipe diameters, wave periods, wave heights, and current velocities. Wave generator and current generator were used for the experiments. Two current directions were used ; co-direction and counter direction to the waves. With the experimental results, the correlations between the scour depths and non-dimensional parameters such as Keulegan-Carpenter number(KC), Froude number(Fr), Ursell number(Ur) and velocity ratio were analysed. The relative scour depths were found obviously to be dominated by the wave component when the velocity ratio function approaches zero and those are gorverned by the current component when the velocity ratio approaches unity. Velocity ratio function was approved to be a proper parameter which is able to express the change of the scour in the combined wave and current zone. Also considering the orbital velocity and the current velocity into Fr numer and KC number respectively, scour depths show more favorable correlationship with the parameters.
Stochastic Reliability Analysis of Armor Units of Rubble-Mound Breakwaters Subject to Multiple Loads
Lee, Cheol-Eung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 2, 2012, Pages 138~148
DOI : 10.9765/KSCOE.2012.24.2.138
A stochastic reliability analysis model has been developed for evaluating the time-dependent stability performance of armor units of rubble-mound breakwaters subjected to the multiple loads of arbitrary magnitudes which could be occurred randomly. The initial structural capacities and the damage rates of armor units of rubble-mound breakwaters could be estimated as a function of the incident wave height with a given return period by using the modified Hudson`s formula and Melby`s formula. The structural stability performances of armor units of rubble-mound breakwaters could be analyzed in detail through the lifetime reliability investigations according to the limit states such as the serviceability or ultimate limit state and the conditions of multiple loads. Finally, repair intervals for the structural management of armor units of rubble-mound breakwaters could quantitatively be evaluated by a new approach suggested in this paper that has been based on the target probability for repair and the accumulated probabilities of failure obtained from the present stochastic reliability analysis model.