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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 23, Issue 6 - Dec 2009
Volume 23, Issue 5 - Oct 2009
Volume 23, Issue 4 - Aug 2009
Volume 23, Issue 3 - Jun 2009
Volume 23, Issue 2 - Apr 2009
Volume 23, Issue 1 - Feb 2009
Selecting the target year
Computations of Natural Convection Flow Using Hermite Stream Function Method
Kim, Jin-Whan ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 1~8
This paper is a continuation of the recent development on Hermite-based divergence free element method and deals with a non-isothermal fluid flow thru the buoyancy driven flow in a square enclosure with temperature difference across the two sides. The basis functions for the velocity field consist of the Hermite function and its curl while the basis functions for the temperature field consists of the Hermite function and its gradients. Hence, the number of degrees of freedom at a node becomes 6, which are the stream function, two velocities, the temperature and its x and y derivatives. This paper presents numerical results for Ra = 105, and compares with those from a stabilized finite element method developed by Illinca et al. (2000). The comparison has been done on 32 by 32 uniform elements and the degree of approximation of elements used for the stabilized finite element are linear (Deg. 1) and quadratic (Deg. 2). The numerical results from both methods show well agreements with those of De vahl Davi (1983).
Experimental Investigation of the Bow Configuration Influence on the Green Water on FPSO
Lee, Hyun-Ho ; Lim, Ho-Jeong ; Rhee, Shin-Hyung ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 9~14
The green water on deck has many harmful effects on the vessel in rough seas such as damages to hull structures, damages to cargos, increase of the downtime, decrease of the stability, and so on. Floating Production Storage and Offloading vessels (FPSOs) are operated in a specific location and are normally positioned to meet mostly head or bow waves in order to reduce the roll motions. But this makes FPSOs more vulnerable to green water around the bow region therefore the bow shape should be properly designed to mitigate the green water damage. In this paper, experimental results in regular head waves for three kinds of bow shapes are compared and some design considerations are proposed, with the building a database for computational fluid dynamics (CFD) validation in mind.
Studies on Variable Liquid-Column Oscillator for High Efficiency Floating Wave Energy Conversion System
Yang, Dong-Soon ; Cho, Byung-Hak ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 15~24
The results of a simulation study of variable liquid column oscillations in U-tanks with a novel control scheme are presented. The configuration under investigation is analogous to that of the tuned liquid-column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. However, by virtue of an adequate controller, the response of amplitude of the U-tanks becomes larger in a desired frequency range. The motion of wave energy conversion system equipped with a variable liquid column oscillator is described by a series of nonlinear differential equations. The equations describe the motion of body under ocean wave excitation, and the motion of liquid with an air-spring effect caused by the compression and expansion of air in vertical liquid columns and air chambers. It is shown that the effect of the air-spring has a vital role to maintain the natural frequency of oscillation in the system to synchronize with the frequency of the ocean wave, thus the system provides the most effective mode for energy extraction from the ocean.
Analysis of Flows around the Rotor-Blades as Rotating Body System of Wind Turbine
Kim, Don-Jean ; Kwag, Seung-Hyun ; Lee, Kyong-Ho ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 25~31
The most important component of wind turbine is rotor blades. The developing method of wind turbine was focused on design of rotor blade. By the way, the design of a rotating body is more decisive process in order to adjust the performance of wind turbine. For instance, the design allows the designer to specify the wind characteristics derived by topographical map. The iterative solver is then used to adjust one of the selected inputs so that the desired rotating performance which is directly related to power generating capacity and efficiency is achieved. Furthermore, in order to save the money for manufacturing the rotor blades and to decrease the maintenance fee of wind power generation plant, while decelerating the cut-in speed of rotor. Therefore, the design and manufacturing of rotating body is understood as a substantial technology of wind power generation plant development. The aiming of this study is building-up the profitable approach to designing of rotating body as a system for the wind power generation plant. The process was conducted in two steps. Firstly, general designing and it’s serial testing of rotating body for voltage measurement. Secondly, the serial test results above were examined with the CFD code. Then, the analysis is made on the basis of amount of electricity generated by rotor-blades and of cut-in speed of generator.
Microstructural Development of
Ceramics Containing Aligned
Bae, Byoung-Chan ; Park, Dong-Soo ; Seo, Won-Chan ; Bang, Kook-Soo ; Park, Chan ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 32~38
Silicon nitride samples with aligned whisker seeds were prepared with different amounts of yttria and alumina as the sintering additives. Their sintering behaviors and the microstructural developments between
were examined. The sample with larger amount of the sintering additives showed faster densification and grain growth. Even though addition of the aligned whisker seeds slightly retarded densification of silicon nitride, it improved the flexural strength and the fracture toughness. Both the flexural strength and the fracture toughness of silicon nitride with the aligned whisker seeds were increased as the amount of the sintering additives was increased.
A Study on the Deformation Characteristics of a Slipper Bearing for High Pressure Piston Pump
Koh, Sung-Wi ; Kim, Byung-Tak ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 39~44
The hydrostatic slipper bearing is generally used in high pressure axial piston pumps to support the load generated from two surfaces which are sliding relatively at low speed. The object of the bearing is to remove the possibility of direct contact by maintenance of an adequate oil film thickness between two metal surfaces. Because the bearing performance is influenced by the bearing deformation, it is highly dependent on the injection pressure, the bearing surface profile and so on. In this study, the deformation characteristics of a hydrostatic slipper bearing is investigated according to the injection pressure by the finite element analysis. In the analysis, the special boundary condition to take the fluid-structure interaction (FSI) into account is used on the interactive surface. The results, such as bearing deformation, stress and lifting force, obtained from the fully coupled analysis are compared with those from the single step sequential method.
Fatigue Characteristics of Engine Rubber Mount for Automotive
Suh, Chang-Min ; Oh, Sang-Yeob ; Park, Dae-Kyu ; Jang, Ju-Ho ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 45~53
In this study, Finite Element Analysis (FEA) was used to decide three kinds of material property of vibration proof rubber with the unique characteristic of non-linear and large deformation. As well, three types of hardness (Hs 50, 55, 60) were compared with the result of fatigue tests, fatigue life was able to be predicted. The request for fatigue life becomes strict more and more as increasing stress under conditions like a compaction, high load and high temperature for parts because it is main characteristics of rubber mount for automotive. Regarding to the fatigue life under dynamic deformation condition, it can be predicted as checking forced deformation extends and its frequency and its strain-life curve. As for material property tests of uniaxial tension test, uniaxial compression test, pure shear test, Ogden model was used for FEA by observing relations between stress and strain's rate as curve fitting. As a result of FEA, fatigue life for rubber mount was predicted and accorded well with the experimental data of fatigue test with hourglass specimens. In addition, its property of the predictable fatigue life method suggested in this study was accorded well with the experimental data by comparing the predicted fatigue life of FEA with the result of fatigue test for rubber component of engine rubber mount.
Evaluation on Basic Properties of Crushed Sand Mortar in Freezing-Thawing and Sulfate Attack
Kim, Myeong-Sik ; Baek, Dong-Il ; Choi, Kang-Seok ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 54~60
Exposed to various environments, concrete confronts degradation by a lot of physical and chemical reaction. Though so many experiments and theorizations on the single condition of concrete degradation have been carried out by constant studies, the truth for now is that there are few studies on the compound phenomenon of degradation related with marine environments. Accordingly, this study measured the degree of degradation in the change of external shape, the change of unit weight and compressive strength, ultrasonic velocity test, and the change of length, etc. after exposing the specimen of cement mortar to the environment between 0 cycle and the maximum of 300 cycles under the condition of aquatic curing, freezing and thawing, and compound degradation, using mineral admixture effective for concrete degradation as a binder. The result indicated that the case of adding mineral admixture showed greater resistance than that of using OPC only, and specifically, the specimen with the additive of slag powder and three component system showed very excellent resistance to freezing and thawing, and compound degradation.
Virtual Goal Method for Homing Trajectory Planning of an Autonomous Underwater Vehicle
Park, Sung-Kook ; Lee, Ji-Hong ; Jun, Bong-Huan ; Lee, Pan-Mook ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 61~70
An AUV (Autonomous Underwater Vehicle) is an unmanned underwater vessel to investigate sea environments and deep sea resource. To be completely autonomous, AUV must have the ability to home and dock to the launcher. In this paper, we consider a class of homing trajectory planning problem for an AUV with kinematic and tactical constraints in horizontal plane. Since the AUV under consideration has underactuated characteristics, trajectory for this kind of AUV must be designed considering the underactuated characteristics. Otherwise, the AUV cannot follow the trajectory. Proposed homing trajectory panning method that called VGM (Virtual Goal Method) based on visibility graph takes the underactated characteristics into consideration. And it guarantees shortest collision free trajectory. For tracking control, we propose a PD controller by simple guidance law. Finally, we validate the trajectory planning algorithm and tracking controller by numerical simulation and ocean engineering basin experiment in KORDI.
Comparison of Buckling Check Formulas and Optimal Design
Jang, Beom-Seon ; Cho, Ho-Young ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 71~78
In ship design or offshore structure design, the evaluation of buckling strength (or ultimate strength) is critical to the determination of scantling of stiffened plates. For this reason, it is useful to study the effect of applying different formula or the relationship between stiffened plate with buckling utilization factor (UF). It can facilitate a designer to decide how much the scantling should be reinforced or how much can be reduced for an optimal design. This paper conducts a comparative study for three buckling check methods; DNV-Ship-Rule, DNV-RP-C201, DNV-PULS. The capacity curves and 2D contour plot for utilization factors versus bi-axial in-plane stresses are compared. The contour plots of DNV-Ship-Rule and DNV-PULS show smoothly increasing trends of UF as the applied in-plane stresses increase, however that of DNV-RP-C201 shows rapidly increasing trend as the applied stresses go beyond transverse buckling stress. A sensitivity analysis is performed to investigate the influence level of each parameter of a stiffened plate on UF. Resulting from the analysis, plate thickness is identified to be the most affective parameter to UF regardless of the buckling check methods. Based on the addressed study, optimal designs for bottom plate of 165 K tanker corresponding to three formulas are compared with each other. DNV-PULS yields 1 mm and 2 mm less thickness than DNV-Ship-Rule and DNV-RP-C201, respectively.
Characteristic Evaluation according to Heat Treatment Conditions of Super Duplex Stainless Steel with Additive 0.2% N - Part 2: Fatigue Crack Propagation Behavior
Ahn, Seok-Hwan ; Kang, Heung-Joo ; Seo, Hyun-Soo ; Nam, Ki-Woo ; Lee, Kun-Chan ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 79~84
Super duplex stainless steel has long life in severe environments by showing the enough strength and corrosion resistance. Therefore, the fracture mechanics approach needs to support the structural strength integrity for the used material. In this study, fatigue crack propagation behavior was investigated to super duplex stainless steel with 0.2% nitrogen. The various volume fraction and distribution of austenite structure for applied specimen in test were obtained by changing the heat treatment temperature and cycle. From test results, fatigue crack propagation rate showed two kinds of tendency between da/dN and
according to distribution of austenite structure and structure anisotropy.
Characteristic Evaluation according to Heat Treatment Conditions of Super Duplex Stainless Steel with Additive 0.2% N - Part 3: Corrosion Characteristic
Ahn, Seok-Hwan ; Kang, Heung-Joo ; Seo, Hyun-Soo ; Nam, Ki-Woo ; Lee, Kun-Chan ;
Journal of Ocean Engineering and Technology, volume 23, issue 5, 2009, Pages 85~91
A stainless steel that contains aggressive negative ion was known to decrease the corrosion resistance. Stainless steel with super corrosion resistance was developed for improvement of corrosion resistance. Super duplex stainless steel is widely used under sever environment because of good mechanical properties and corrosion resistance. Also, Super duplex stainless steel has long life in severe environments by showing the enough strength and corrosion resistance. But duplex stainless steel is not stabilized compared to austenite stainless steel in corrosion resistance. In this study, corrosion characteristic were investigated to super duplex stainless steel with additive 0.2% nitrogen with
thin films coated or no coated by sol-gel method in 3.5% NaCl. From test results, corrosion current density in the heat-treated specimen for
phase precipitation was higher than that of different heat-treated specimen. Also,
colloidal-coated specimen had not occurred almost corrosion.