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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 18, Issue 6 - Dec 2004
Volume 18, Issue 5 - Oct 2004
Volume 18, Issue 4 - Aug 2004
Volume 18, Issue 3 - Jun 2004
Volume 18, Issue 2 - Apr 2004
Volume 18, Issue 1 - Feb 2004
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Analysis of Impulse Turbine for Wave Energy Conversion Using CFD Method
HYUN BEOM-SOO ; MOON JAE SEUNG ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 1~6
This paper deals with the performance analysis and design of impulse turbine for owe type wave energy plant. Numerical analysis is performed using a commercial software FLUENT. This parametric study includes the variation of several important parameters, such as the number and shape of blades, hub ratio, and tip clearance. Since parametric study at various flow coefficients requires a considerable amount of computing time, two-dimensional analysis is employed to find out optimum principal particulars. Full three-dimensional calculations are also performed for several test cases, in order to confirm the validity of the two-dimensional approach. Up to the present stage, tentative results are demonstrated the usefulness of 2-D analysis.
Wave Control by an Array of Porous Dual Cylindrical Structures
CHO IL-HYOUNG ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 7~14
The interaction of incident manochromatic waves with an array of N surface-piercing porous dual cylindrical structures is investigated in the frame of three-dimensional linear potential theory. The dual cylindrical structure is camposed of concentric two cylinders. The exterior cylinder is porous and the interior cylinder is impermeable. The fluid domain is divided into N+1 regions i.e. a single exterior region and N interior regions. The diffraction potentials in each region representing the scattering of incident waves by an array of porous cylindrical structures are expressed by the Fourier Bessel series. The unknown coefficients in each region are determined by applying the porous boundary condition and continuity of mass flux at the matching boundary. It is found that an array of porous cylindrical structures reduces both the wave forces and the wave run-up, and shows the excellent performance of wave blocking. The results show that various types of breakwater exchanging seawater are prospective by controlling the porosity and the configuration of cylindrical structures.
Numerical Analysis of Flow-Induced Noise by Vortex-Edge Interaction
KANG HO-KEUN ; KIM EUN-RA ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 15~21
An edge tone is the discrete tone or narrow-band sound produced by an oscillating free shear layer, impinging on a rigid surface. In this paper, we present a 2-D edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle, using the finite difference lattice Boltzmann method (FDLBM). We use a modified version of the lattice BGK compressible fluid model, adding an additional term and allowing for longer time increments, compared to a conventional FDLBM, and also use a boundary fitted coordinates system. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of
= 23. At a stand-off distance, the edge is inserted along the centerline of the jet, and a sinuous instability wave, with real frequency, is assumed to be created in the vicinity of the nozzle and propagates towards the downstream. We have succeeded in capturing very small pressure fluctuations, resulting from periodical oscillations of a jet around the edge. The pressure fluctuations propagate with the speed of sound. Its interaction with the wedge produces an non-rotational feedback field, which, near the nozzle exit, is a periodic transverse flow, producing the singularities at the nozzle lips.
Numerical Prediction of Tidal Current due to the Density and Wind-driven Current in Yeong-il Bay
YOON HAN-SAM ; LEE IN-CHEOL ; RYU CHEONG-RO ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 22~28
This study constructed a 3D real-time numerical model that predicts the water quality and movement characteristics of the inner bay, considering the characteristics of the wind-driven current and density current in estuaries, generated by the river discharge from the Hyeong-san river and oceanic water of the Eastern sea. The numerical model successfully calculated the seawater circulation current of Yeong-il Bay, using the input conditions oj the real-time tidal current, river discharge, and weather conditions during March 2001. This study also observed the wind-driven current and density current in estuaries that are effected by the seawater circulation pattern of the inner bay. We investigated and analyzed each impact factor, and its relationship to the water quality of Yeong-il bay.
Optimization and Verification of Parameters Used in Successive Zooming Genetic Algorithm
KWON YOUNG-DOO ; KWON HYUN-WOOK ; KIM JAE-YONG ; JIN SEUNG-BO ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 29~35
A new approach, referred to as a successive zooming genetic algorithm (SZGA), is proposed for identifying a global solution, using continuous zooming factors for optimization problems. In order to improve the local fine-tuning of the GA, we introduced a new method whereby the search space is zoomed around the design variable with the best fitness per 100 generation, resulting in an improvement of the convergence. Furthermore, the reliability of the optimized solution is determined based on the theory of probability, and the parameter used for the successive zooming method is optimized. With parameter optimization, we can eliminate the time allocated for deciding parameters used in SZGA. To demonstrate the superiority of the proposed theory, we tested for the minimization of a multiple function, as well as simple functions. After testing, we applied the parameter optimization to a truss problem and wicket gate servomotor optimization. Then, the proposed algorithm identifies a more exact optimum value than the standard genetic algorithm.
3D Non-linear Analysis of Interlaminar Stress around the Hole Edge of Orthotropic Laminates
SONG KWAN-HYUNG ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 36~42
Orthotropic laminates, such as [
]s and [
]s, were performed, using a commercial nonlinear finite element method. Interlaminar stress distributions, around the hole curve free-edge, were calculated. The delamination bearing strengths of pin joints were predicted, using the modified delamination failure criterion. These stress distributions were presented along the radial lines and around the free-edge of the hole. Further, three-dimensional non-linear contact analysis of orthotropic laminates was conducted to investigate the effect of friction. In this paper, laminates with a circular hole were taken to study interlaminar stresses the curved edge. This study may assist in the design of a thick composite laminate with mechanically pin joints.
Effect of Stress Ratio on Fatigue Fracture of a Shot Peening Marine Structural Steel
PARK KYOUNG-DONG ; JIN YOUNG-BEOM ; PARK HYOUNG-DONG ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 43~49
The lightness of components required in the automobile and machine industry necessitates the use of high strength components. In particular, the fatigue failure phenomena, which occurs when using metal, increases the danger to human life and property. Therefore, antifatigue failure technology is an integral part of current industries. Currently, the shot peening is used for removing the defect from the surface of steel, while improving the fatigue strength on surface. Therefore, in this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in a stress ratio(R=0.1, R=0.3, R=0.6) was investigated, giving consideration to fracture mechanics. By using the methods mentioned above, following conclusions are drawn: (1) The fatigue crack growth rate(da/dN) of the shot-peening material was lower than that of the un-peening material and in stage I, ΔKth, the threshold stress intensity factor of the shot-peen processed material is high in critical parts, unlike the un-peening material. Also m, fatigue crack growth exponent and number of cycle of the shot-peening material, was higher than that of the un-peening material, as concluded from effect of da/dN. (2) Fatigue life shows more improvement in the shot-peening material than in the un-peening material, and the compressive residual stress of surface on the shot-peen processed operate resistance of fatigue crack propagation.
On Corrosion Behaviors in Welded Zone of API 5L-X65 Steel for Natural Gas Transmission
JO SANG-KEUN ; SONG HAN-SEOP ; KONG Yu-SIK ; KIM YOUNG-DAI ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 50~56
This study is on the constant-current stress corrosion test, related to the load stress, in both the welded and non-welded zones of high tensile strength steel that is used for natural gas transmission. The surface corrosion pattern of the welded zone of API 5L-X65 specimens for natural gas transmission showed general corrosion and narrow pitting, and the pitting was increased with load stress. Initially, the average relative electrode potential and the average relative current of the high tensile strength steel, used for natural gas transmission specimens, were decreased rapidly, and the average relative electrode potential was higher and the average relative current was lower in welded zone, compared to base metal. The average relative electrode potential was decreased with load stress, and the average relative current was somewhat increased by increasing the load stress. The corrosion rate was less in welded zone, compared to base metal, and the corrosion rate was decreased by increasing the load stress.
Comparison of the Stern Forms and Resistance Characteristics for G/T 47,000 Class Mid-size Cruise Ships
KIM DONG-JOON ; PARK HYUN-SOO ; HYUN BEOM-SOO ; KIM MOO-LONG ; CHOI KYUNG-SIK ;
Journal of Ocean Engineering and Technology, volume 18, issue 5, 2004, Pages 57~63
Various propulsion systems, applicable for a G/T 47,000 class mid-size cruise ship, are discussed and a comparative study on stern forms and hull resistance characteristics is carried out, in relation to these propulsion systems. Based on shipyard production logs on similar cruise ships, a reference hull form of a single shaft propulsion system with center-skeg, is generated. Then two new stern hull forms are derived by using a hull transform technique: consisting of one stern form using a twin-skeg system and the other using the Azipod system. Using a CFD-based commercial flaw analysis program, WAVIS (WAve and VIScous flaw analysis system for hull form development), various hydrodynamic characteristics, including wave profiles and ship hull resistance, are compared for three hull forms.