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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 26, Issue 6 - Dec 2012
Volume 26, Issue 5 - Oct 2012
Volume 26, Issue 4 - Aug 2012
Volume 26, Issue 3 - Jun 2012
Volume 26, Issue 2 - Apr 2012
Volume 26, Issue 1 - Feb 2012
Selecting the target year
Semi-resolution Practicability of Three-Dimensional Statics of Cables from Computer Programs
Dodaran, Asgar Ahadpour ; Park, SangKil ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 1~6
DOI : 10.5574/KSOE.2012.26.6.001
The purpose of this paper is to present a rational method for analyzing, designing, or evaluating the spread mooring systems used with floating drilling units. This paper presents a validated model to calculate the catenary static configuration. A semi-resolution approach is presented in this paper that is capable of predicting the static performance of a caisson mooring system. The solution is derived as a function of only three parameters, which can be solved numerically by implementing different kinds of boundary conditions. The efficiency and accuracy of the method permit quick parametric studies for the optimal selection of the system particle, which is undoubtedly useful for a preliminary design. A number of numerical examples demonstrate the validity of the adopted approach. The paper contains a complete description of the test cases and reports the results in such a way that it can provide a "benchmark" test for users and programmers of computer codes for flexible riser analysis.
Numerical Study on Wave-induced Motion of Offshore Structures Using Cartesian-grid based Flow Simulation Method
Nam, Bo Woo ; Kim, Yonghwan ; Yang, Kyung Kyu ; Hong, Sa Young ; Sung, Hong Gun ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 7~13
DOI : 10.5574/KSOE.2012.26.6.007
This paper presents a numerical study of the wave loads acting on offshore structures using a Cartesian-grid-based flow simulation method. Finite volume discretization with a volume-of-fluid (VOF) method is adopted to solve two-phase Navier-Stokes equations. Among the many variations of the VOF method, the CICSAM scheme is applied. The body boundary conditions are satisfied using a porosity function, and wave generation is carried out by using transient (wave or damping) zone approaches. In order to validate the present numerical method, three different basic offshore structures, including a sphere, Pinkster barge, and Wigley model, are numerically investigated. First, diffraction and radiation problems are solved using the present numerical method. The wave exciting and drift forces from the diffraction problems are compared with potential-based solutions. The added mass and wave damping forces from the radiation problems are also compared with the potential results. Next, the wave-induced motion responses of the structures are calculated and compared with the existing experimental data. The comparison results are fairly good, showing the validity of the present numerical method.
Study on Hull Form Development and Resistance Performance of High Speed Aluminum Leisure Boat
Jeong, Uh-Cheul ; Kim, Do-Jung ; Choi, Hong-Sik ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 14~18
DOI : 10.5574/KSOE.2012.26.6.014
A 30ft class aluminum leisure boat is newly developed and the resistance performances are investigated by a model test at a high-speed circulating water channel. The effect of a fin attached to the side of the hull is studied at two different displacements. Wave patterns are observed to make clear the relationship between the resistance performance and wave characteristics. It can be found that a chine position at the draft line can have a strong effect on the resistance performance around a certain velocity range.
Experimental Study on Unconfined Compression Strength and Split Tensile Strength Properties in relation to Freezing Temperature and Loading Rate of Frozen Soil
Seo, Young-Kyo ; Choi, Heon-Woo ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 19~26
DOI : 10.5574/KSOE.2012.26.6.019
Recently the world has been suffering from difficulties related to the demand and supply of energy due to the democratic movements sweeping across the Middle East. Consequently, many have turned their attention to never-developed extreme regions such as the polar lands or deep sea, which contain many underground resources. This research investigated the strength and initial elastic modulus values of eternally frozen ground through a uniaxial compression test and indirect tensile test using frozen artificial soil specimens. To ensure accurate test results, a sandymud mixture of standard Jumunjin sand and kaolinite (20% in weight) was used for the specimens in these laboratory tests. Specimen were prepared by varying the water content ratio (7%, 15%, and 20%). Then, the variation in the strength value, depending on the water content, was observed. This research also established three kinds of environments under freezing temperatures of
. Then, the variation in the strength value was observed, depending on the freezing environment. In addition, the tests divided the loading rate into 6 phases and observed the variation in the stress-strain ratio, depending on the loading rate. The test data showed that a lower freezing temperature resulted in a larger strength value. An increase in the ice content in the specimen with the increase in the water content ratio influenced the strength value of the specimen. A faster load rate had a greater influence on the uniaxial compression and indirect tensile strengths of a frozen specimen and produced a different strength engineering property through the initial tangential modulus of elasticity. Finally, the long-term strength under a constant water content ratio and freezing temperature was checked by producing stress-strain ratio curves depending on the loading rate.
Microstructure and Impact Toughness of Weld Metal in Multipass Welded Super Duplex Stainless Steel
Seo, Won-Chan ; Park, Chan ; Bang, Kook-Soo ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 27~32
DOI : 10.5574/KSOE.2012.26.6.027
The effects of reheating during welding on the microstructure and impact toughness of weld metal in 25% Cr super duplex stainless steels were investigated. Using different heat inputs, weld metals with different reheated regions were obtained. This showed that, depending on the reheating temperature, the microstructure in the reheated region was quite different from that of the as-deposited microstructure. When reheated into the
temperature range, fine intragranular austenite was formed in the as-deposited columnar structure. However, when reheated above the
solvus temperature range, most of the columnar structure disappeared and fine equiaxed austenite and ferrite were formed. Because of the larger amount of fine austenite in the reheated region, a higher impact toughness was obtained in the weld metal with a higher amount of reheated region.
CFD Analysis of Underwater Standard Penetration Test Equipment
Ko, Jin Hwan ; Jang, In Sung ; Kim, Woo Tae ; Kwon, O Soon ; Baek, Won Dae ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 33~38
DOI : 10.5574/KSOE.2012.26.6.033
In our study, a closed-type penetration unit for standard penetration test (SPT) equipment was developed in order to operate in an underwater environment. This type causes energy dissipation, mainly due to the small gap between an airtight case and moving hammer. The dissipation was estimated through a CFD analysis. The computed dissipated energy was less than 1.2% compared to the potential energy of the hammer with the given gap. Subsequently, the impact energy of the underwater SPT equipment was within 1.2% of that for the SPT equipment on land.
Design and Performance Analysis of Ducted Propulsor for Underwater Robot
Kim, Kyung-Jin ; Lee, Doo-Hyoung ; Park, Warn-Gyu ; Park, Han-Il ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 39~45
DOI : 10.5574/KSOE.2012.26.6.039
Underwater robots are generally used for the construction of seabed structures, deep-sea ecosystem research, ocean energy development, etc. A ducted marine propulsor is widely used for the thruster of an underwater robot because of its collision protection, efficiency increase, cavitation reduction, etc. However, the flow of a ducted propeller is very complex because it involves strong flow interactions between the blade impeller and duct. The present work aimed to design a ducted propeller using 2-D strip theory and CFD analysis. The hydrodynamic forces (i.e. and ) were computed to set the local angle of attack in a spanwise direction of the propeller blade. After the propeller design, performance coefficients such as the thrust, torque, and efficiency were computed to check whether the designed performance was achieved. To validate the present analysis, the thrust was compared with experimental data and good agreement was obtained.
Experimental Study of Motion Behavior of Side-by-Side Moored Two Floating Bodies Including Sloshing in Head Sea
Cho, Seok-Kyu ; Sung, Hong-Gun ; Hong, Jang-Pyo ; Hong, Sa-Young ; Hong, Seok-Won ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 46~52
DOI : 10.5574/KSOE.2012.26.6.046
The motions and drift forces of side-by-side moored FSRU and LNGC including the sloshing effect, were studied using experiments. The FSRU and LNGC contained LNG cargo tanks and the LNG sloshing could affect the motions and drift forces of the structures due to its coupling with floating body motion. The effect of coupling can vary with the LNG filling level, and the effect of the filling level was investigated. The coupling effect was stronger at lower filling level. It was confirmed that longitudinal sloshing influenced the surge and surge mean drift force in head sea. In addition, gap flow affected the sway and mean drift forces. Sloshing attenuated the sway and yaw excited by gap flow in side-by-side configuration.
Experimental Study of Hydrodynamic Performance of Backward Bent Duct Buoy (BBDB) Floating Wave Energy Converter
Kim, Sung-Jae ; Kwon, Jinseong ; Kim, Jun-Dong ; Koo, Weoncheol ; Shin, Sungwon ; Kim, Kyuhan ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 53~58
DOI : 10.5574/KSOE.2012.26.6.053
An experimental study on the hydrodynamic performance of a backward bent duct buoy (BBDB) was performed in a 2D wave tank. The BBDB is one of the promising oscillating water column (OWC) types of floating wave energy converters. Two different corner-shaped BBDBs (sharp-corner and round-corner) were used to measure the maximum chamber surface elevations and body motions for various incident wave conditions, and their hydrodynamic characteristics were compared. In order to investigate the effect of the pneumatic pressure inside the chamber, the heave and pitch angle interacted with elevations were compared for both open chamber and partially open chamber BBDBs. From the comparison study, the deviation in the chamber surface elevations between the two shapes of BBDBs was found to be significant near the resonance period, which may be explained by viscous energy loss. It was also found that the pneumatic pressure noticeably affected the chamber surface elevation and body motions.
Study of 7 Degree of Freedom Desktop Master Arm
Choi, Hyeungsik ; Lee, Dong-Jun ; Ha, Kyung-Nam ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 59~65
DOI : 10.5574/KSOE.2012.26.6.059
In this research, a novel mater arm was studied as a teaching device for an underwater revolute robot arm used as a slave arm. The master arm was designed to be a seven-degree-of-freedom (DOF) structure, with a structure similar to that of the slave arm, and to be desktop size to allow it to be worn on a human arm. The master arm with encoders on the joints was used as an input device for teaching a slave robot arm. In addition, small electric magnets were installed at the joints of the master arm to generate the haptic force. A control system was designed to sense excessive force and torque in the joints of the master arm and protect it by controlling the position and velocity of the slave arm through the encoder signal of the master arm.
Structural Design Equation for a Box-shape Pressure Compensated Chamber of Pilot Mining Robot
Lee, Minuk ; Hong, Sup ; Lim, Woochul ; Lee, Tae Hee ; Choi, Jong-Su ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 66~73
DOI : 10.5574/KSOE.2012.26.6.066
A pressure compensated chamber of a pilot mining robot isolates and protects an electrical-electronic system from the ambient highly pressured water. Since the inner pressure of the chamber is compensated with outer water pressure using hydraulic oil and pressure compensator, there exists a pressure difference, less than 1 bar, between outer and inner surface. The structural safety of the chamber is obtained relatively easier than the canister type which inner pressure is kept as the atmospheric pressure. However, due to the adoption of box shape for space efficiency and usage of the transparent engineering plastic viewport for checking inner circumstance, the viewport can be largely deformed. This large deformation can cause an additional tensile force, called the prying force, to the bolt-flange connection parts of the viewport. In this paper, we suggest the structural design equation considering the prying action for designing the structure of a box-shape pressure compensated chamber.
Numerical Analysis of Ship Local Resistance
Park, Dong-Woo ; Seo, Jang-Hoon ; Yoon, Hyun-Sik ; Chun, Ho-Hwan ; Jung, Jae-Hwan ; Kim, Mi-Jeong ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 74~79
DOI : 10.5574/KSOE.2012.26.6.074
The present study aims at suggesting the systematic approach to analyze the local drag components as the resistance performance characterized by the flow of the ship. In order to identify the local areas, the hull surface is decomposed into SVM (Station-Vertical Section Map) which consists of 20 stations along the longitudinal direction and 20 sections along the vertical direction (from the bottom to the waterline). Successively, on the SVM, the friction and pressure drag coefficients as the components of total drag coefficient have been analyzed for two different hull forms of Wigley and KVLCC by using CFD.
Study of Reliability-Based Robust Design Optimization Using Conservative Approximate Meta-Models
Sim, Hyoung Min ; Song, Chang Yong ; Lee, Jongsoo ; Choi, Ha-Young ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 80~85
DOI : 10.5574/KSOE.2012.26.6.080
The methods of robust design optimization (RDO) and reliability-based robust design optimization (RBRDO) were implemented in the present study. RBRDO is an integrated method that accounts for the design robustness of an objective function and for the reliability of constraints. The objective function in RBRDO is expressed in terms of the mean and standard deviation of an original objective function. Thus, a multi-objective formulation is employed. The regressive approximate models are generated via the moving least squares method (MLSM) and constraint-feasible moving least squares method (CF-MLSM), which make it possible to realize the feasibility regardless of the multimodality/nonlinearity of the constraint function during the approximate optimization processes. The regression model based RBRDO is newly devised and its numerical characteristics are explored using the design of an actively controlled ten bar truss structure.
Semi-submersible Drilling Rig and Drilling Equipment
An, Byoung-Ky ; Oh, Hyun-Jung ;
Journal of Ocean Engineering and Technology, volume 26, issue 6, 2012, Pages 86~92
DOI : 10.5574/KSOE.2012.26.6.086
An exploration well is drilled where oil or gas potential is shown by a seismic survey and interpretation. With the advance of drilling technology, most of the easily accessible oil had been developed by the end of the 20th century. To satisfy the ever increasing demand for oil, and bolstered by high oil prices, the major oil companies started to drill in deep water, which requires a deep offshore drilling unit. Offshore drilling units are generally classified by their maximum operating water depth. Many semi-submersible rigs have been purpose-designed for the drilling industry as the allowable drilling water depth has become deeper by the developed technics since the first semi-submersible was launched in 1963. Semi-submersible rigs are commonly used for shallow to deep water up to 3,000 m. Drilling equipment such as a top drive, blowout preventer, drawworks and power system, mud circulation system, and subsea wellhead system are explained to help with an understanding of offshore drilling procedures in the oil and gas fields. The objective of this paper is to introduce the main components of a semi-submersible rig and, by doing so, to raise the awareness of offshore drilling, which accounts for over 30% of the total oil production and will continue to increase.