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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 27, Issue 6 - Dec 2015
Volume 27, Issue 5 - Oct 2015
Volume 27, Issue 4 - Aug 2015
Volume 27, Issue 3 - Jun 2015
Volume 27, Issue 2 - Apr 2015
Volume 27, Issue 1 - Feb 2015
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Analysis of Nonlinear Destructive Interaction between Wind and Wave Loads Acting on the Offshore Wind Energy Converter based on the Hydraulic Model Test
Cho, Yong Jun ; Yang, Kee Sok ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 281~294
DOI : 10.9765/KSCOE.2015.27.5.281
In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed,
, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.
Effect of Energy Loss by a Vertical Slotted Wall
Cho, Il-Hyoung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 295~303
DOI : 10.9765/KSCOE.2015.27.5.295
The eigenfunction expansion method is appled for the wave scattering by a vertical slotted, where both the inertial and quadratic drag terms are involved. Quadratic drag term representing the energy loss is linearized by the application of socalled equivalent linearization. The drag coefficient, which was empirically determined by Yoon et al.(2006) and Huang(2007) is used. Analytical results are verified by comparison to the experimental results conducted by Kwon et al.(2014) and Zhu and Chwang(2001). Using the developed design tool, the effect of energy loss by a vertical slotted wall is estimated with various design parameters, such as porosity, submergence depth, shape of slits and wave characteristics. It is found that the maximum value of energy loss across the slotted wall is generated at porosity value less than P = 0.1. The present solutions can provide a good predictive tools to estimate the wave absorbing efficiency by a slotted-wall breakwater.
Impact Assessment of Sea_Level Rise based on Coastal Vulnerability Index
Lee, Haemi ; Kang, Tae soon ; Cho, Kwangwoo ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 304~314
DOI : 10.9765/KSCOE.2015.27.5.304
We have reviewed the current status of coastal vulnerability index(CVI) to be guided into an appropriate CVI development for Korean coast and applied a methodology into the east coast of Korea to quantify coastal vulnerability by future sea_level rise. The CVIs reviewed includes USGS CVI, sea_level rise CVI, compound CVI, and multi scale CVI. The USGS CVI, expressed into the external forcing of sea_level rise, wave and tide, and adaptive capacity of morphology, erosion and slope, is adopted here for CVI quantification. The range of CVI is 1.826~22.361 with a mean of 7.085 for present condition and increases into 2.887~30.619 with a mean of 12.361 for the year of 2100(1 m sea_level rise). The index "VERY HIGH" is currently 8.57% of the coast and occupies 35.56% in 2100. The pattern of CVI change by sea_level rise is different to different local areas, and Gangneung, Yangyang and Goseong show the highest increase. The land use pattern in the "VERY HIGH" index is dominated by both human system of housing complex, road, cropland, etc, and natural system of sand, wetland, forestry, etc., which suggests existing land utilization should be reframed in the era of climate change. Though CVI approach is highly efficient to deal with a large set of climate scenarios entailed in climate impact assessment due to uncertainties, we also propose three_level assessment for the application of CVI methodology in the site specific adaptation such as first screening assessment by CVI, second scoping assessment by impact model, and final risk quantification with the result of impact model.
Dispersion Characteristics of Wave Forces on Interlocking Caisson Breakwaters by Cross Cables
Seo, Ji Hye ; Yi, Jin Hak ; Park, Woo Sun ; Won, Deck Hee ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 315~323
DOI : 10.9765/KSCOE.2015.27.5.315
Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.
An Analytical Study on Generation of Pore-Water Pressures Induced by Flow and Waves in Seabed, and Resulting Liquefaction
Lee, Kwang-Ho ; Kim, Dong-Wook ; Kim, Do-Sam ; Bae, Ki-Seong ; Jeon, Jong-Hyeok ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 324~338
DOI : 10.9765/KSCOE.2015.27.5.324
Analytical solutions for interaction between seabed and waves such as progressive wave or partial standing wave with arbitrary reflection ratio or standing wave have been developed by many researchers including Lee et al.(2014; 2015a; 2015b; 2015c; 2015d) and Yamamoto et al.(1978). They handled the pore-water pressure as oscillating pore-water pressure and residual pore-water pressure separately and discussed the seabed response on each pore-water pressure. However, based on field observations and laboratory experiments, the oscillating and residual pore-water pressures in the seabed do occur not separately but together at the same time. Therefore, the pore-water pressure should be investigated from a total pore-water pressure point of view. Thus, in this paper, the wave-induced seabed response including liquefaction depth was discussed among oscillating, residual, and total pore-water pressures' point of view according to the variation of wave, seabed, and flow conditions. From the results, in the field of flow with the same direction of progressive wave, the following seabed response has been identified; with increase of flow velocity, the dimensionless oscillating pore-water pressure increases, but the dimensionless residual pore-water pressure decreases, and consequently the dimensionless total pore-water pressure and the dimensionless liquefaction depth decrease.
The Influence of Suction Foundation Models for Offshore Wind Turbine
Jang, Hwa Sub ; Nam, Hyun Woo ; Kwak, Yeon Min ; Yoon, Se Woong ; Kim, Ho Sun ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 339~344
DOI : 10.9765/KSCOE.2015.27.5.339
Suction piles have been widely used as foundations and anchor systems in offshore industry, and recently, it have been tried to be used as foundations for offshore wind turbines. Many researches have shown that stiffness of a foundation could effect dynamic responses of a offshore wind turbine so that appropriate modeling application of wind turbine foundations is recommended. In this paper, we calculate a stiffness matrix of a suction foundation through 3D FEM analysis and compare the results with the ones calculated by conventional formula for estimating stiffness of shallow foundations. And then we carry out integrated load analysis for the evaluation of dynamic responses and natural frequencies of the structure using the calculated stiffness matrix. The results shows that the effect of load in the mudline is not large, but in the case of assuming the foundation as a fixed support, the natural frequency is over-estimated up to 10%. Therefore, considering stiffness of foundations is recommended when you evaluate the natural frequencies of wind turbine structures.
Hydraulic Experiments on Transmission Coefficients for Vertical Structure under Intermediate Water Depth Condition
Kim, Young-Taek ; Lee, Jong-In ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 345~352
DOI : 10.9765/KSCOE.2015.27.5.345
Two-dimensional hydraulic model experiments on vertical structures were conducted to investigate wave transmission characteristics under irregular wave condition. The formula about transmission coefficient for the vertical structure was suggested and the results were compared with Goda(1969). Since Goda(1969)'s tests were conducted based on regular waves, the results showed the discrepancy with this study. The Goda's results were relatively higher than the results from the present study. An influence parameter was quantitatively suggested in this study to consider the effect of structural design factors such as the width of structures, the water depth, and the wave length on the wave transmission, while Goda(1969) suggested the mean, upper and lower limits of parameters for the vertical wall(d=h). The transmission coefficients and energy conservation for zero-freeboard conditions were analyzed.
Subsurface Water Storage Using Coastal Aquifers Filled With Saline Water
Jung, Eun Tae ; Park, Namsik ; Kim, In Chul ; Lee, Seoung Hwi ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 353~357
DOI : 10.9765/KSCOE.2015.27.5.353
A new method is proposed for water resources using aquifers in coastal areas. These aquifers are generally filled with saline water due to seawater intrusion and consequently being left unutilized. Surface water can be injected into these aquifers and recovered for water quality enhancement and stored water. Injection and pumping wells are used. For this technique to be successful protection of pumping well from seawater intrusion is an essential issue. Salt water pumping can be used to prevent saline water upconing. Numerical analysis demonstrated that a properly designed and executed salt water pumping well can protect a freshwater pumping well from salt water intrusion.
Analysis of Working Time at the Test Site of Southwest Offshore Wind Project in Korea Based on Weather Window
Kim, Min Suek ; Kim, Ji Young ; Kwak, Ji Yeong ; Kang, Keum Seok ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 358~363
DOI : 10.9765/KSCOE.2015.27.5.358
As a preparation process for successful establishment of demonstration offshore wind farm, analyses have been made for working time at the construction site where working time is defined as the time available for marine operation to take place under given weather conditions. Data used are hourly wave and wind data from met mast, HeMOSU-1, and 3 hour numerical model data from Korea Meteorological Administration (KMA). Seasonal results show the minimum working time during winter and moderate during autumn and spring. The most working time was seen during summer on average. Monthly analyses show the most working time in May, June, and August which was higher than the working time in July and September. Working time reaches at steady state and no significant change was seen above wave height of 1.5 m and wind speed of 8 m/s.
The Design Development on the Mooring System of a Floating Barge Positioned in the Shallow Water Zone
Kim, Young-Bok ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 27, issue 5, 2015, Pages 364~371
DOI : 10.9765/KSCOE.2015.27.5.364
This study is aimed to develop the dynamic analysis technique for a floating aquaculture in a shallow water region under the harsh sea condition. In case of the installation region to transform from a coastal area to the offshore area, the influence of sea bed with sea waves on the mooring lines was announced to be significant by other authors. In this study, the numerical tool was developed to solve dynamic behavior of the floating barge coupled with mooring lines in a shallow zone of the sea considering the influence of sea bed on the floating system.