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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 25, Issue 6 - Dec 2011
Volume 25, Issue 5 - Oct 2011
Volume 25, Issue 4 - Aug 2011
Volume 25, Issue 3 - Jun 2011
Volume 25, Issue 2 - Apr 2011
Volume 25, Issue 1 - Feb 2011
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Analytical Research of Topside Installation in Mating phase with Crane Vessel
Lee, Jong-Hyun ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 1~6
DOI : 10.5574/KSOE.2011.25.4.001
The installation of a topside structure can be categorized into the following stages: start, pre-lifting, lifting, lifted, rotating, positioning, lowering, mating, and end of installation. The transfer of the module onto the floating spar hull occurs in the last three stages, from lowering to the end. The coupled multi-body motions are calculated in both calm water and in irregular waves with a significant wave height (1.52m). The effects of the hydrodynamic interactions between the heavy lifting vessel and the spar hull during the lowering and mating stages are considered. The internal forces caused by the load transfer and ballasting are derived for the mating phases. The results of the internal forces for the calm water condition are compared with those in the irregular sea condition. Although the effect of the pitch motion on the relative vertical motion between the deck of the floating structure and the topside module is significant in the mating phases, the internal force induced pitch motion is too small to have this influence. However, the effect of the internal force on the wave-induced heave responses in the mating phases is noticeable in the irregular sea condition because transfer mass-induced draught changes for the floating structure are observed to have higher amplitudes than the external force induced responses. The impacts of the module on the spar hull in the mating phase are investigated.
Dynamic Analysis of Topside Module in Lifting Installation Phase
Lee, Jong-Hyun ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 7~11
DOI : 10.5574/KSOE.2011.25.4.007
The installation phase for a topside module suggested can be divided into 9 stages, which include start, pre-lifting, lifting, lifted, rotating, positioning, lowering, mating, and end of installation. The transfer of the topside module from a transport barge to a crane vessel takes place in the first three stages, from start to lifting, while the transfer of the module onto a floating spar hull occurs in the last three stages, from lowering to the end. The coupled multi-body motions are calculated in both calm water and in irregular waves with significant wave height (1.52m), with suggested force equilibrium diagrams. The effects of the hydrodynamic interactions between the crane vessel and barge during the lifting stage have been considered. The internal forces caused by the load transfer and ballasting are derived for the lifting phases. The results of these internal forces for the calm water condition are compared with those in the irregular sea condition. Although the effect of pitch motion on the relative vertical motion between the deck of the floating structure and the topside module is significant in the lifting phases, the internal force induced pitch motion is too small to show its influence. However, the effect of the internal force on the wave-induced heave responses in the lifting phases is noticeable in the irregular sea condition because the transfer mass-induced draught changes in the floating structure are observed to have higher amplitudes than the external force induced responses.
Creep Behavior of 9% Ni Alloy Steel at Elevated Temperatures
Suh, Chang-Min ; Oh, Sang-Yeob ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 12~17
DOI : 10.5574/KSOE.2011.25.4.012
Little design data is available for the creep life prediction of 9% Ni alloy in elevated temperatures. Therefore, in this study, a series of creep tests under 16 combined conditions with 4 kinds of stresses and 4 temperatures was performed to obtain creep design and life prediction data for 9% Ni alloy, with the following results. The stress exponents decreased as the test temperature increased. The creep activation energy gradually decreased as the stresses became larger. The Larson-Miller parameter (LMP) constant for this alloy was estimated to be about 2.
Potential Flow Analysis around Ship with Goose-neck Type Bulbous Bow Penetrating Free Surface
Choi, Hee-Jong ; Park, Il-Heum ; Kim, Jong-Kyu ; Kim, Ok-Sam ; Chun, Ho-Hwan ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 18~22
DOI : 10.5574/KSOE.2011.25.4.018
The Ranking source panel method was used to predict the flow phenomenon of a ship with a goose-neck type bulbous bow penetrating the free surface. The non-linearity of the free surface boundary condition was fully satisfied using an iterative calculation method, and the raised panel method was adopted to obtain a more stable solution at each iteration step. The panel cutting method was applied to generate a hull calculation grid at each iteration step, including the first step. At that time, the nose of the goose-neck type bulbous bow was divided by the free surface and the free surface panel was modified at each iteration step using the variable free surface panel method. Numerical calculations were performed to investigate the validity and efficiency of the applied numerical algorithm using the 3600 TEU container carrier. The computed wave resistance coefficients were compared with the experimentally achieved residual resistance coefficients.
Calibration of Water Velocity Profile in Circular Water Channel Using Particle Image Velocimetry
Suh, Sung-Bu ; Jung, Kwang-Hyo ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 23~27
DOI : 10.5574/KSOE.2011.25.4.023
This experimental study was performed to find rpms of the impeller and the surface flow accelerator to make a uniform velocity vertical distribution in the circular water channel. PIV technique was employed to measure the water velocity profiles into the water depth from the free surface. The number of instantaneous velocity profiles was decomposed into mean and turbulence velocity components, and the distribution of velocity fluctuation and turbulence intensity were computed for each experimental condition. From these results, the velocity uniformity was quantitatively determined to present the flow quality in the measuring section of the circular water channel. It has been shown that the proper operation of the surface flow accelerator would make the uniform velocity profiles and reduce the velocity fluctuation near the free surface.
Numerical Analysis of Wave-induced Motion of Floating Pendulor Wave Energy Converter
Nam, Bo-Woo ; Hong, Sa-Young ; Kim, Ki-Bum ; Park, Ji-Yong ; Shin, Seung-Ho ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 28~35
DOI : 10.5574/KSOE.2011.25.4.028
In this paper, the wave-induced motion characteristics of a floating pendulor are investigated numerically. A floating pendulor is a movable-body-type wave energy converter. This device consists of three main parts (floater, pendulum, and damping plates). In order to obtain the hydrodynamic coefficients and wave exciting forces acting on floating bodies, a higher-order boundary element method (HOBEM) using a wave Green function is applied to the present problems. The hinged motion of a pendulum is simulated by applying the penalty method. In order to obtain a more realistic motion response for a pendulor, numerical body damping is included. First, the wave force and motion characteristics of just a floater are observed with respect to different shape parameters. Then, a coupled analysis of a floater, pendulum, and damping plates is carried out. The relative pitch velocity and wave forces acting on the floating pendulor are compared with those of a fixed pendulor.
Direct forcing/fictitious domain-Level set method for two-phase flow-structure interaction
Jeon, Chung-Ho ; Yoon, Hyun-Sik ; Jung, Jae-Hwan ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 36~41
DOI : 10.5574/KSOE.2011.25.4.036
In the present paper, a direct forcing/fictitious domain (DF/FD) level set method is proposed to simulate the FSI (fluid-solid interaction) in two-phase flow. The main idea is to combine the direct-forcing/fictitious domain (DF/FD) method with the level set method in the Cartesian coordinates. The DF/FD method is a non-Lagrange-multiplier version of a distributed Lagrange multiplier/fictitious domain (DLM/FD) method. This method does not sacrifice the accuracy and robustness by employing a discrete
(Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, easy implementation, and utilization of the original governing equation without modification. Simulations of various water-entry problems have been conducted to validate the capability and accuracy of the present method in solving the FSI in two-phase flow. Consequently, the present results are found to be in good agreement with those of previous studies.
Design Optimization of Wake Equalizing Duct Using CFD
Lee, Ho-Sung ; Kim, Dong-Joon ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 42~47
DOI : 10.5574/KSOE.2011.25.4.042
In this paper, wake equalizing duct (WED) form optimization was carried out using computational fluid dynamics (CFD) techniques. A WED is a ring-shaped flow vane with a foil-type cross-section fitted to a hull in front of the upper propeller area. The main advantage of a WED is the power savings resulting from the uniformity of the velocity distribution on the propeller plane, a reduction in the flow separation at the aft-body, and lift generation with a forward force component on the foil section. This paper intends to evaluate these functions and find an optimized WED form for minimizing the viscous resistance and equalizing the wake distribution. In the optimization process, the study uses four WED parameters: the angle of the section, longitudinal location, and angles of the axes for the half rings against the longitudinal and transverse planes of the ship. KRISO 300K VLCC2 (KVLCC2) is chosen as an example ship to demonstrate the WED optimization. The optimization procedure uses genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-II(NSGA-II) for Multiobjective Optimization. The results show that the optimized WED can reduce the viscous resistance at the expense of the uniformity of the wake distribution.
Proposal for Improvement in Prediction of Marine Propeller Performance Using Vortex Lattice Method
Suh, Sung-Bu ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 48~53
DOI : 10.5574/KSOE.2011.25.4.048
Current trends in propeller design have led to the need for extremely complex blade shapes, which place great demands on the accuracy of design and analysis methods. This paper presents a new proposal for improving the prediction of propeller performance with a vortex lattice method using the lifting surface theory. The paper presents a review of the theory and a description of the numerical methods employed. For 8 different propellers, the open water characteristics are calculated and compared with experimental data. The results are in good agreement in the region of a high advanced velocity, but there are differences in the other case. We have corrected the parameters for the trailing wake modeling in this paper, and repeated the calculation. The new calculation results are more in agreement with the experimental data.
Application of Inclusive Environmental Impact Assessment for Newly-Proposed Airport in Korea
Lee, Hee-Su ; Park, Jong-Chun ; Kim, Hyo-Seob ; Jang, Chang-Hwan ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 54~58
DOI : 10.5574/KSOE.2011.25.4.054
The need and importance of developing and utilizing the oceans, not only as sources of renewable energy and mineral resources, but also as countermeasures to global warming such as for CCS (carbon capture and storage), have continued to increase, especially in countries with limited land areas and resources. Therefore, it is necessary to assess the sustainability of an ocean utilization technology or system not only from an economic point of view but also from an ecological one. For this purpose, it might be effective to develop a comprehensive evaluation method and/or index, by which the assessment of and decisions about a technology and system can be made more objectively. It would also be useful to have an environmental simulation model, which was developed and reported in a previous research. The aim of this study was to modify a reasonable and quantitative index, with which a comprehensive evaluation system can be established, to assess environmental sustainability and risk.
Impedance-based Long-term Structural Health Monitoring for Tidal Current Power Plant Structure in Noisy Environments
Min, Ji-Young ; Shim, Hyo-Jin ; Yun, Chung-Bang ; Yi, Jin-Hak ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 59~65
DOI : 10.5574/KSOE.2011.25.4.059
In structural health monitoring (SHM) using electro-mechanical impedance signatures, it is a critical issue for extremely large structures to extract the best damage diagnosis results, while minimizing unknown environmental effects, including temperature, humidity, and acoustic vibration. If the impedance signatures fluctuate because of these factors, these fluctuations should be eliminated because they might hide the characteristics of the host structural damages. This paper presents a long-term SHM technique under an unknown noisy environment for tidal current power plant structures. The obtained impedance signatures contained significant variations during the measurements, especially in the audio frequency range. To eliminate these variations, a continuous principal component analysis was applied, and the results were compared with the conventional approach using the RMSD (Root Mean Square Deviation) and CC (Cross-correlation Coefficient) damage indices. Finally, it was found that this approach could be effectively used for long-term SHM in noisy environments.
Flexural strength properties of MoSi
Lee, Sang-Pill ; Lee, Hyun-Uk ; Lee, Jin-Kyung ; Bae, Dong-Su ;
Journal of Ocean Engineering and Technology, volume 25, issue 4, 2011, Pages 66~71
DOI : 10.5574/KSOE.2011.25.4.066
The flexural strength of
based composites reinforced with Nb sheets has been investigated, based on the detailed examination of their microstructure and fractured surface. Both sintered density and porosity of Nb/
composites were also examined. Nb/
composites were fabricated by different conditions such as temperature, applied pressure and its holding time, using a hot-press device. The volume fraction of Nb sheet in this composite system was fixed as 10%. The characterization of Nb/
composites were investigated by means of optical microscopy, scanning electron microscope and three point bending test. Nb/
composites represented a dense morphology at the interfacial region, accompanying the creation of two types of reaction layer by the chemical reaction of Nb and
composites possessed an excellent density at the fabricating temperature of
, corresponded to about 95% of theoretical density. The flexural strength of Nb/
romposites were greatly affected by the pressure holding time at the same fabricating temperature, owing to the large suppression of porosity in the microstructure. Especially, Nb/
composites represented a good flexural strength of about 310 MPa at the fabricating condition of
, 30MPa and 60min, accompanying the pseudo-ductile fracture behavior by the deformation of Nb sheet and the interfacial delamination.