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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 17, Issue 6 - Dec 2003
Volume 17, Issue 5 - Oct 2003
Volume 17, Issue 4 - Aug 2003
Volume 17, Issue 3 - Jun 2003
Volume 17, Issue 2 - Apr 2003
Volume 17, Issue 1 - Feb 2003
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Large Eddy Simulations on the Configuration Design of Afterbodies for Drag Reduction
PARK JONC-CHUN ; KANG DAE-HWAN ; CHUN HO-HWAN ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 1~10
When a body with slant angle behind its shoulder is moving at a high speed, the turbulent motion around the afterbody is generally associated with the flow separation, and determines the normal component of the drag. By changing the slant angle of the afterbody, the drag coefficients can be changed, drastically. Understanding and controlling the turbulent separated flows has significant importance for the design of optimal configuration of the moving bodies. In this paper, a new Large Eddy Simulation technique has been developed to investigate turbulent vortical motions around the afterbodies, using slant angle. By understanding the structure of the turbulent flow around the body, the new configuration of afterbodies is designed to reduce the drag of body, and the nonlinear effects, due to the interaction between the body configuration and the turbulent separated flows, are investigated by use of the developed LES technique.
An Incompressible Flow Computation by a Hierarchical Iterative Preconditioning
KIM JIN WHAN ; JEONG CHANG-RYUL ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 11~18
In two-dimensional incompressible flows, a preconditioning technique called Hierarchical Iterative Procedure (HIP) has been implemented on a SUPG finite element formulation. By using the SUPG formulation, one can escape from the LBB constraint hence, achieving an equal order formulation. In this paper, we increased the order of interpolation up to cubic. The conjugate gradient squared (CGS) method is used for the outer iteration, and the HIP for the preconditioning for the incompressible Navier-Stokes equation. The hierarchical elements have been used to achieve a higher order accuracy in fluid flow analyses, but a proper and efficient iterative procedure for higher order finite element formulation has not been available, thus far. The numerical results by the present HIP for the lid driven cavity flow showed the present procedure to be stable, very efficient, and useful in flow analyses, in conjunction with hierarchical elements.
On the Wave Source Identification of an Wave Maker Problem
JANG TAEK-SOO ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 19~24
The question of wave source identification in a wave maker problem is the primary objective of the this paper. With the observed wave elevation, the existence of the wave maker velocity is discussed with the help of the mathematical theory of inverse problems. Utilizing the property of the Strum-Liouville system and compactness, the uniqueness and the ill-posedness(in the sense of stability) for the identification are proved.
A Study on the Characteristics of the Stem Wave in front of the Coastal Structure
PARK HYO-BONG ; YOON HAN-SAM ; RYU CHEONG-RO ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 25~31
Numerical experiments have been conducted using the nonlinear combined refraction-diffraction model, in order to analyze the generation characteristics of stem wave, which is formed by the interaction between vertical structure and the oblique incident waves. The results of stem wave are discussed through the stem wave height distribution along/normal vertical structure, under the wide range of incident wave conditions-wave heights, periods, depths, and angles. Under the same wave height and period, the larger the incident wave angle, the higher the stem wave heights. According to the results of wave height distribution, in front of vertical structure, the maximum of stern wave heights occurs in the location bordering the vertical wall. Furthermore, the most significant result is that stem waves occur under the incident angles between
, and the stem wave height ratio has the maximum value, which is approximately 1.85 times the incident wave height when the incident wave angle becomes
Spatial and Temporal Variation Characteristics between Water Quality and Pollutant Loads of Yeong-il Bay (II) - Mutual Variation between Inflowing Pollutant Loads and Water Quality -
YOON HAN-SAM ; LEE IN-CHEOL ; RYU CHEONG-RO ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 32~38
This study investigates the distribution characteristics and relationship of water quality, and analyzes the spatial and temporal variation and distribution of the pollutant loads at Yeong-il Bay. The results of these analysis, the concentrations of nutrient loads (T-N and T-P), both appeared to be at the maximum value in November, while most small values were taken in May for the T-N, and in August for the T-P. For COD, the maximum concentration was in August, which has much precipitation during the same season, T-N was at the mean, and T-P was at the minimum value. Using the cluster analysis to develop the division of the sea basin by the dendrogram, before and after construction of Pohang New-port, the variation characteristics of water quality of Yeong-il Bay were discussed. The in flowing pollutant loads were transported to the landward by the high-density salinity water volume of the bottom layer therefore, it formed nutrient trap or coastal trapping areas of the pollutant load. By this mechanism, it is clear that the water volume with high-density nutrient exists on both sides of the Pohang New-port. Thus, the sea basins increasing concentration of the pollutant load at Yeong-il Bay are most prevalent at Hyeong-san estuary, the Pohang Old, and New-port. To improve water quality of this sea basin, the reduction of these nutrients loads should be the highest priority.
A Study on the Reinforced Method of Doubler Plate in Ship Hull Structure
HAM JUH-HYEOK ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 39~47
A study of the structural strength evaluation on the doubler plate, considering various load cases that were subjected to in-plane and out of plane combined load, has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate for various load cases, elasto-plastic large deflection analysis is introduced, including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed, based on the results. In order to compare the doubler structure with the original strength of main plate, without doubler, simple formulas for the evaluation of the equivalent flat plate thickness are derived for each load case, respectively, based on the additional series of analysis of flat plate structure. Using these derived equations, the thickness change of an equivalent flat plate is analyzed according to the variation of various design parameters of doubler platesome design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas are discovered, and these relations are formulated for the future development of simple strength evaluation formula of general doubler plate structure.
Ultimate Strength Analysis of Ring-stiffened Cylinders with Initial Imperfections( I )
PARK CHI-MO ; PARK DONG-MIN ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 48~56
This paper has developed an efficient nonlinear finite element method that covers both initial deformations and initial stresses of general distribution in calculating the ultimate strength of ring-stiffened cylinders. The developed method and two widely-used commercial codes (NASTRAN and ABAQUS) were simultaneously applied to the same analysis model within the extent of those commercial codes' coverage to check the validity of the present method. After the validity check, it was used for parametric studies for more general cases of initial stress distribution, which produced some useful information about the imperfection sensitivity of the ultimate strength of ring-stiffened cylinders.
Structure-Control Combined Design with Structure Intensity
PARK JUNG-HYEN ; KIM SOON HO ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 57~65
This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback
controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the
norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and
norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.
Finite Element Analyses of Cylinder Problems Using Pseudo-General Plane Strain Elements(Planar Constraint)
KWON YOUNG-DOO ; KWON HYUN-WOOK ; SHIN SANG-MOK ; LEE CHAN-BOK ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 66~75
Long cylinder, subjected to internal pressure, is important in the analysis and design of nuclear fuel rod structures. In many cases, long cylinder problems have been considered as a plane strain condition. However, strictly speaking, long cylinder problems are not plane strain problems, but rather a general plane strain (GPS) condition, which is a combination of a plane strain state and a uniform strain state. The magnitude of the uniform axial strain is required, in order to make the summation of the axial force zero. Although there has been the GPS element, this paper proposes a general technique to solve long cylinder problems, using several pseudo-general plane strain (PGPS) elements. The conventional GPS elements and PGPS elements employed are as follows: axisymmetric GPS element (GA3), axisymmetric PGPS element (PGA8/6), 2-D GPS element (GIO), 3-D PGPS element (PG20/16), and reduced PGPS elements (RPGA6, RPG20/16). In particular, PGPS elements (PGA8/6, PG20/16) can be applied in periodic structure problems. These finite elements are tested, using several kinds of examples, thereby confirming the validity of the proposed finite element models.
Friction Welding of Spheroidal Graphite Cast Iron and 2024 Aluminium Alloys using Insert Metal
KIM CHANG-GYU ; KIM CHI-OK ; KIM KWANG-ILL ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 76~81
Friction welding of GCD45 spheroidal graphite cast iron and 2024 aluminum alloy has been studied, especially in terms of the joint faces and strength of friction welding. For appropriate results of the friction welding of GCD45 graphite cast iron and 2024 aluminum alloy, an insert of A1050 pure aluminum metal was used. The joint strength of the A1050 pure aluminum insert approached the maximum strength of 165.7Mpa, compared to 128MPa for the joint between GCD45 graphite cast iron and A1050 pure aluminum without the insert metal. Maximum strength, 165.7Mpa, was possible for the following optimum conditions: 20MPa for the friction pressure, P1, 60MPa for the upsetting pressure, P2, 1 second for the friction time, t1, 3000rpm for the rotation, N, and 0.3 seconds for the brake time, tB.
A Study on the Sharing Architecture of FMS for Small and Medium Enterprises on Distributed Heterogeneous Environments
PARK JE-WOONG ; KIM WON-JUNG ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 82~87
A practical method to investigate the sharing architecture of FMS, for small and medium enterprises, on distributed heterogeneous environmental conditions is investigated. Because the industrial FMS model requires a reasonable size for actual work-site flexible operation, the initial facility expense is very heavy. The support for flexible cooperation of FMS, with some external different FMS, can reduce expenditures and provide greater functionality. While most FMS provide their operation process using an adequate mechanism, when used in isolation, such as island of automation, there is increasing demand for FMS that can cooperate. By exchanging intermediate products and information with other external FMS, products can be produced that cannot be produced alone, such as those that require various processes. This study first considers the sharing architecture of FMS for small and medium enterprises, and investigates the effects of the general sharing architecture of FMS on distributed heterogeneous environments, by using transducer approach to agentification. In this study, set-up station or in-out station takes charge of the gateway of intermediate products, and routes them among distributed heterogeneous FMS plants. The transducer approach is applied to web agent and set-up agent established interfaces, with system controller and setup controller. In this study, the FMS-established sharing architecture is able to obtain not only the internal flexibility, but also the external flexibility.
A Study on the Hull Form Development of the 25 Knots Class Planing Hull Form Fishing Boat
LEE KWI-JOO ; JOA SOON-WON ; PARK MYUNG-KYU ; SHIN YOUNG-KYUN ;
Journal of Ocean Engineering and Technology, volume 17, issue 5, 2003, Pages 88~94
A series of tests of 5 model ships, selected from a data survey of 10 Gross Tonnage actual fishing boats, were performed in two circulating water channels (Chosun University in Korea and WJFEL in Japan), in order to develop the basic hull form of a 25 knots-class fishing boat. Resistance tests, trim and sinkage measurements and wave pattern observations etc., were included in each I1wdel test, and the model test results were compared and analyzed. The result was as follows: P-4 hull form ship changed into Deep V type bow is the best hull form with good performance, especially with regard to ship's resistance efficiency.