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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
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Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 28, Issue 6 - Dec 2014
Volume 28, Issue 5 - Oct 2014
Volume 28, Issue 4 - Aug 2014
Volume 28, Issue 3 - Jun 2014
Volume 28, Issue 2 - Apr 2014
Volume 28, Issue 1 - Feb 2014
Selecting the target year
Fatigue Damage Model Comparison with Tri-modal Spectrum under Stationary Gaussian Random Processes
Park, Jun-Bum ; Jeong, Se-Min ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 185~192
DOI : 10.5574/KSOE.2014.28.3.185
The riser systems for floating offshore structures are known to experience tri-modal dynamic responses. These are owing to the combined loadings from the low-frequency response due to riser tension behavior, middle-range frequency response coming from winds and waves, and high-frequency response due to vortex induced-vibration. In this study, fatigue damage models were applied to predict the fatigue damages in a well-separated tri-modal spectrum, and the resultant fatigue damages of each model were compared with the most reasonable fatigue damage calculated by the inverse Fourier transform of the spectrum, rain-flow counting method, and Palmgren-Miner rule as a reference. The results show that the fatigue damage models developed for a wide-band spectrum are applicable to the tri-modal spectrum, and both the Benasciutti-Tovo and JB models could most accurately predict the fatigue damages of the tri-modal spectrum responses.
Analytic Investigation of Multi-Component Elastic Cables under 3-D Concentrated Static Loads
Choi, Yoon-Rak ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 193~198
DOI : 10.5574/KSOE.2014.28.3.193
An elastic cable with piecewise constant properties under the action of concentrated static loads is studied analytically. Analytic solutions for catenary cables are combined at the discontinuous points caused by the discontinuous elastic properties or concentrated loads. The application of the boundary conditions at both ends of the multi-component cable results in three algebraic non-linear equations for three unknown parameters, which are determined numerically. The solutions for the shape, tension, elongation, and cross-sectional contraction of the cable are expressed in closed forms. Some examples are given for cases of two- and three-dimensional loads.
CFD Simulations and Experimental Tests for Three Different Ducted Propellers
Joung, Tae-Hwan ; Jeong, Seong-Jae ; Lee, Seung-Keon ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 199~208
DOI : 10.5574/KSOE.2014.28.3.199
In this study, propeller open water characteristics (
) were compared for three different ducted propellers using a Computational Fluid Dynamics (CFD) analysis, as well as an experimental test at a basin. The best shape of the duct was selected from the three types of specially designed ducts based on the CFD analysis results. The same propeller model (Kaplan type propeller) was used inside all three duct models, and the propeller open water characteristics were compared, predominantly at the design speed for an underwater vehicle. Finally, the results of the CFD test simulations for the selected duct case were verified by experimental open water tests in a towing tank.
Experimental Study of Water Impact Loads on Symmetric and Asymmetric Wedges
Kim, Kyong-Hwan ; Lee, Dong Yeop ; Hong, Sa Young ; Kim, Young-Shik ; Kim, Byoung Wan ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 209~217
DOI : 10.5574/KSOE.2014.28.3.209
In the present study, the water impact loads on two-dimensional symmetric and asymmetric wedges were mainly studied. The impact pressure and force were measured during a vertical drop of the symmetric and asymmetric wedges. The measured pressure was compared with analytic solutions. The measured force at a local area of the wedge was compared with the integrated pressures and analytic solutions. Some findings on symmetric and asymmetrical wedge drops are presented, and the reliability of the force sensor used for the measurement of the local impact force is discussed.
Design Optimization and Reliability Analysis of Jacket Support Structure for 5-MW Offshore Wind Turbine
Lee, Ji-Hyun ; Kim, Soo-Young ; Kim, Myung-Hyun ; Shin, Sung-Chul ; Lee, Yeon-Seung ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 218~226
DOI : 10.5574/KSOE.2014.28.3.218
Since the support structure of an offshore wind turbine has to withstand severe environmental loads such as wind, wave, and seismic loads during its entire service life, the need for a robust and reliable design increases, along with the need for a cost effective design. In addition, a robust and reliable support structure contributes to the high availability of a wind turbine and low maintenance costs. From this point of view, this paper presents a design process that includes design optimization and reliability analysis. First, the jacket structure of the NREL 5-MW offshore wind turbine is optimized to minimize the weight and stresses, while satisfying the design requirements. Second, the reliability of the optimum design is evaluated and compared with that of the initial design. Although the present study results in a new optimum shape for a jacket support structure with reduced weight and increased reliability, the authors suggest that the optimum design has to be accompanied by a reliability analysis during the design process, as well as reliability based design optimization if needed.
Reflection and Hydraulic Characteristics inside Two-Chamber Vertical Slit Caisson in 3-D Oblique Wave Field
Hur, Dong-Soo ; Lee, Jun ; Lee, Woo-Dong ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 227~235
DOI : 10.5574/KSOE.2014.28.3.227
Using a 3-D numerical scheme (LES-WASS-3D) that considered wave-structure-sandy seabed interactions in a 3-D wave field, we analyzed the wave reflection and hydraulic characteristics inside a slit caisson with two chambers in a 3-D oblique wave field. To verify the 3-D numerical analysis method suggested in this study, we compared the numerical results with existing experimental results and found good agreement. The numerical analysis revealed that a standing wave field is generated on the front side of the slit caisson due to the effect of wave reflection. For incident waves propagating perpendicular to the slit caisson, the nodes and anti-nodes of the standing wave are apparent and symmetrical. However, in an oblique wave field, as the incident wave angle decreases, the nodes and anti-nodes of the standing wave become ambiguous and unsymmetrical. It was also found that the wave reflection coefficient decreases as the incident wave angle decreases. It can be pointed out that as the incident wave angle decreases, the turbulent intensity in the chamber increases. Thereby, the increased wave energy dissipation by the increased turbulent intensity reduces the rate of wave reflection. In addition, a strong turbulent intensity generally occurs in the first chamber.
Marine Environmental Characteristics of Seagrass Habitat in Seomjin River Estuary
Ji, Hyeong-Seok ; Seo, Hee-Jeong ; Kim, Myeong-Won ; Lee, Moon Ock ; Kim, Jongkyu ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 236~244
DOI : 10.5574/KSOE.2014.28.3.236
This study considered a seagrass habitat in order to analyze the characteristics of a marine environment of seagrass located in the Seomjin river estuary, through an analysis of the distribution of the water depth, field observation, and three-dimensional numerical experiments using an EFDC model. The seagrass habitat was usually distributed at D.L(-) 0.5~0.0 m, and was hardly seen in the intertidal zone higher than that range. The distribution of the water temperature was within the range of
, and the seagrass was demonstrated to have a strong tolerance to changes in the water temperature. In addition, the salinity distribution was found to be 27.2~31.0 psu, with suspended solids of 32.1 mg/L, which were higher than the previous research results (Huh et al., 1998), implying that there may be a reduction in the amount of deposits caused by the suspended solids. As for the sedimentary facies, they were comprised of 62.7% sand, 19.1% silt, and 18.2% clay, indicating that the arenaceous was superior and the sedimentary facies were similar to that of Dadae Bay. According to a numerical experiment, the maximum tidal current was 75 cm/s, while the tidal residual current was 10 cm/s, confirming that it sufficiently adapted to strong tidal currents. The erosion and deposition are predicted to be less than 1.0 cm/year. Thus, it is judged that the resuspension of sediments due to tidal currents and the changes in sedimentary facies are insignificant.
Improvement Plan of Ocean Physics Assessment Technique for Power Plant Thermal Effluent
Kim, Myeong-Won ; Jo, Gwang-Woo ; Maeng, Jun-Ho ; Kang, Tae-Soon ; Kim, Jongkyu ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 245~253
DOI : 10.5574/KSOE.2014.28.3.245
This research analyzed the current situation and problems with an environmental impact assessment to provide a rational ocean physics assessment technique for power plant thermal effluent. This research also tried to create an improvement plan for heated effluent diffusion impact assessment by examining the reporting regulations for environmental impact assessment, national and international evaluation guidelines, etc. In the case of evaluating the oceanographic impact of heated effluent discharged from power plants, a pre-investigation is necessary before a full-scale presentence investigation, to accurately predict and minimize power plant construction effects on the surrounding environments. Before this presentence investigation, moreover, an integrated presentence plan, which agrees with the business plan, effect prediction, and post-investigation, needs to be established. A sufficient summit investigation must be made, which considers climate changes, and new and additional power plant construction. For accurate long-term oceanic environmental change prediction, the credibility of effect prediction must be elevated by presenting an evaluation method that is categorized by numerical organization models, verification methods, result presentation, and other things. Furthermore, unproductive conflicts between the people involved in heated effluent evaluation should be reduced by these improvement plans.
Feasibility Study on Sampling Ocean Meteorological Data using Stratified Method
Han, Song-I ; Cho, Yong-Jin ;
Journal of Ocean Engineering and Technology, volume 28, issue 3, 2014, Pages 254~259
DOI : 10.5574/KSOE.2014.28.3.254
The infrared signature of a ship is largely influenced by the ocean environment of the operating area, which has been known to cause large changes in the signature. As a result, the weather condition has to be clearly set for an analysis of the infrared signatures. It is necessary to analyze meteorological data for all the oceans where the ship is supposed to be operated. This is impossibly costly and time consuming because of the huge size of the data. Therefore, the creation of a standard environmental variable for an infrared signature research is necessary. In this study, we compared and analyzed sampling methods to represent ocean data close to the Korean peninsula. In order to perform this research, we collected ocean meteorological records from KMA (Korea Meteorological Administration), and sampled these in numerous ways considering five variables that are known to affect the infrared signature. Specifically, a simple random sampling method for all the data and 1-D, 2-D, and 3-D stratified sampling methods were compared and analyzed by considering the mean square errors for each method.