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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Society of Naval Architects of Korea
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Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 46, Issue 6 - Dec 2009
Volume 46, Issue 5 - Oct 2009
Volume 46, Issue 4 - Aug 2009
Volume 46, Issue 3 - Jun 2009
Volume 46, Issue 2 - Apr 2009
Volume 46, Issue 1 - Feb 2009
Selecting the target year
Study on the Effect of Wake Control Devices on Ship Performance Components
Lee, Yeon-Seung ; Choi, Young-Bok ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 453~459
DOI : 10.3744/SNAK.2009.46.5.453
The DSME guide plate(GP) has been developed with the target to improve the cavitation and vibration performance when used with discharging cooling water around the outlet of LNG carrier. It was proven that it could as well be applied as a powerful wake control device on its own, even without discharging cooling water. However, it has to be taken into account that it inevitably results in speed loss. This study shows the possibility to design a GP which simultaneously improves both vibration and speed performance. The study intends to outline how to design the preliminary GP configurations from both the vibration and the speed performance points of view. Further, the study offers design guidance for the hull form and the propeller when adapting GP as a wake control device.
Numerical Study on the Gap Flow of a Rudder System with Bisymmetric Blocking Bar
Oh, Jung-Keun ; Seo, Dae-Won ; Kim, Hyo-Chul ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 460~470
DOI : 10.3744/SNAK.2009.46.5.460
In recent practice a half round prismatic bar has fillet welded or formed through foundry work along the centerline on rear concave surface of the horn to mitigate gap flow between fixed and movable part of the rudder system. When the gap clearance has been blocked with this practice, numerical simulations indicate that the practices are not only effective in reducing the gap flow but also in mitigating the cavitation. The blocking effects are remarkably improved when a pair of blocking bar is bisymmetrically attached with respect to centerline on the opposite convex surface of the movable part. The blocking bar could be placed on the exposed surface under maximum rudder angle. This implies that the blocking bar could be easily adopted not only in a design stage but also in a maintenance stage for mitigating rudder cavitation. In addition, the numerical simulations imply that more improvements could be anticipated through the selection of section shape of prismatic bar for gap flow blocking.
Study on Resistance Performance of Icebreaking Cargo Vessel in Pack Ice Condition according to Variation of Synthetic Ice Thickness and Hull Form Characteristics
Lee, Seung-Ho ; Kim, Moon-Chan ; Chun, Ho-Hwan ; Cho, Jun-Cheol ; Shin, Byung-Chul ; Jung, Un-Hwa ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 471~478
DOI : 10.3744/SNAK.2009.46.5.471
The present paper deals with characteristics of resistance performance according to the variation of synthetic ice thickness and hull form. The resistance test has been conducted with pack ice condition in Pusan National University towing tank. Stem angle has been chosen as main parameters for the variation of hull form characteristics, which is the most important factor especially in icebreaking cargo vessel. The serial comparisons of resistance test have been done with the variation of hull form parameter as well as with the different thickness of synthetic ice. The different trend of resistance performances with increasing of stem angle has been shown at each synthetic ice thickness. The present test results is expected to be confirmed by comparing the test results in ice tank in the near future.
Study on Design of a Twisted Full-Spade Rudder for a Large Container Ship by the Genetic Algorithm
Kim, In-Hwan ; Kim, Moon-Chan ; Lee, Jin-Hee ; Chun, Jang-Ho ; Jung, Un-Hwa ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 479~487
DOI : 10.3744/SNAK.2009.46.5.479
This paper describes the design of a full-spade twisted rudder section by using the genetic algorithm based on VLM(Vortex Lattice Method) and panel method. The developed propeller- rudder analysis program has been validated by comparing with experimental data. The developed code has been used for the design of a twisted full-spade rudder especially for finding out optimum section. The optimization has been firstly carried out by the genetic algorithm. The more detail variation of a rudder section has been also conducted by changing section profile in more detail to confirm the most optimum section profile. The developed new twisted rudder has been compared with existing twisted rudder by cavitation testing in the cavitation tunnel at MOERI. It is concluded that the developed twisted rudder has a lower cavity in comparison with existing twisted rudder. The verification of efficiency gain is expected to be carried out through self-propulsion tests in the near future.
Generation of Freak Waves in a Numerical Wave Tank and Its Validation in Wave Flume
Jeong, Seong-Jae ; Park, Seong-Wook ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 488~497
DOI : 10.3744/SNAK.2009.46.5.488
The freak wave, also known as New-Year-Wave in the north Atlantic, is relatively large and spontaneous ocean surface wave that can sink even large ships and destroy maritime structures. To understand oceanic conditions that develop freak waves, we simulated and generated two versions of scale-downed waves (1:64 and 1:42) in a numerical wave tank and compared the results with the experiment in wave flume. Both of the breaking and non-breaking waves were generated in the simulation. The numerical simulation was implemented based on the finite volume method and a genetic optimization algorithm. Random values were assigned as the initial values for the parameter in the control function, which produced signals representing the motion of wave-maker. The same signal obtained from the optimization process was used for both of the simulation and the experiment. By varying the object function and restrictions of the simulation, a best profile of design wave was selected based on the characteristics, height and period of simulated waves. Results showed that the simulation and experiment with the scale of 1:42 agreed better with freak waves in the natural condition. The presented simulation method will contribute to saving the time and cost for conducting subsequent response analyses of motion under freak waves in the course of the model test for ship and maritime structure.
Cyclic Stress-strain Hardening Model of AC4C-T6 Alloy at Cryogenic Temperature
Lee, Jae-Beom ; Kim, Kyung-Su ; Lee, Jang-Hyun ; Yoo, Mi-Ji ; Choung, Joon-Mo ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 498~509
DOI : 10.3744/SNAK.2009.46.5.498
Present study is concerned with the simulation of plasticity models for the cyclic stressstrain behavior of aluminum alloy AC4C-T6 that can be used for primary materials of LNG cargo pump. Material model of cyclic hardening and plasticity for aluminum alloy AC4C-T6 was investigated through experiments and numerical simulations. Monotonic tensile and cyclic tension-compression test under symmetric load cycles was performed at both room temperature and cryogenic temperature of
. Based on the experimental data plastic hardening models were evaluated for isotropic/kinematic/combined hardening. FEA (Finite Element Analysis) models which describe the cyclic stress-strain relationship were evaluated for the simulation of plasticity. An appropriate hardening model is proposed comparing the results of FEA with those of experiments.
Development of Evaluation System for Fatigue Strength on the Connection Between Longitudinals and Transverse Web
Hong, Ki-Sup ; Kim, Sung-Chan ; Ahn, Jae-Wook ; Kim, Seong-Ki ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 510~519
DOI : 10.3744/SNAK.2009.46.5.510
Ship structure is composed of the welded mixture members which are plate and stiffeners. Ship structure is also influenced by variable loadings such as wave and inertia load. There have been several fatigue damage problems on the connection between longitudinal and transverse web due to wide usage of high tensile steel and adoption of wide web space to improve shipbuilding productivity. It is impossible to estimate the fatigue lives for all connection details through refined fatigue analysis. It is necessary to use the simplified approach for the fatigue life estimation of the connection details. PLUS analysis, which is suggested by the classification society, is one of the simplified approaches and is widely adopted to get fatigue lives for the connection details along whole cargo hold area. However, ship building yards still have difficulties to get fatigue lives due to large amount of calculation and time even if this approach reduce the time and amount of calculation. This paper treats the computing system developed to reduce efforts of estimating the fatigue lives. The influence factors of mean shear stress and local dynamic pressure are easily calculated and fatigue lives for all hot spots can be estimated automatically by the developed computing system. It is possible to reduce computing time and efforts to get the fatigue lives for the connection details between longitudinals and transverse webs along the ship. This system was applied to get fatigue lives on the connection details of a VLCC and verified the availability.
A Framework for Container Stowage Information Exchange Between Ships and Harbors Using RFID and Web Services
Kim, Ik-June ; Han, Soon-Hung ; Paik, Bu-Geun ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 520~526
DOI : 10.3744/SNAK.2009.46.5.520
Efficient stowage plan is required for handling large number of containers in a container terminal. Before a ship enters port, most of container terminals prepare a stowage plan based on information received from the shipping company. If this information does not have the accurate information of containers in the vessel, the stowage plan might be often changed or sometimes it becomes useless. In order to avoid this problem, we apply RFID system in the container ship and we propose a framework for communication between ships and terminals using RFID and Web Services technology.
Suppression of Load Pendulation Using Tagline Control System for Floating Crane
Ku, Nam-Kug ; Cha, Ju-Hwan ; Kwon, Jung-Han ; Lee, Kyu-Yuel ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 527~535
DOI : 10.3744/SNAK.2009.46.5.527
This paper describes the control system to suppress the load pendulation using tagline for the floating crane. Dynamic equation of motion of the floating crane and the load is derived using Newton's 2nd law and free body model. The floating crane and the load are assumed that they move in center plane. Each rigid body has 3 DOF (surge, heave, pitch), because it moves in two directions and rotates. Then, this system, which is composed of two rigid bodies, has 6 DOF. The gravitational force, the hydrostatic force, the hydrodynamic force and the tension of the wire rope are considered as external forces, which affect to the floating crane. To suppress the pendulation of the load, the tagline, which connects between the load and the float crane, is applied to the system. The tagline is composed of the spring and the wire rope. Proportional and Derivative control is used as a linear control algorithm. The results of the numerical analysis of the 3,600 ton floating crane show that the tagline system is effective to suppress the load pendulation.
Numerical Simulation of Electromagnetic Wave Scattering from Offshore Wind Turbine
Kim, Kook-Hyun ; Cho, Dae-Seung ; Choi, Gil-Hwan ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 536~544
DOI : 10.3744/SNAK.2009.46.5.536
The performance of radars operated near an offshore wind farm region may be degraded due to the distorted signals by wind turbines. This degradation of radar systems includes ghost effects and doppler effects by a tower, nacelle, and turbine blades consisting of the wind turbine. In this paper, electromagnetic wave backscatterings from a offshore wind turbine are numerically simulated in terms of temporal radar cross section and radar cross section spectra, using a quasi-static approach based on physical optics and physical theory of diffraction. The simulations are carried out at 3.05 GHz for the seven yaw angles and four blade pitch angles. From the results, radar cross section values and doppler effect as turbine blades rotate are investigated.
Development of Bi-directional Triple-eccentric Type Butterfly Valve
Kim, Soo-Young ; Lee, Dong-Myung ; Bae, Jung-Hoon ; Shin, Sung-Chul ; Sul, Chang-Ho ;
Journal of the Society of Naval Architects of Korea, volume 46, issue 5, 2009, Pages 545~551
DOI : 10.3744/SNAK.2009.46.5.545
In naval architecture and offshore engineering, the development and a broad use has been achieved in the field of flow control valves for pipe system. Butterfly valves are also widely used for flow control, but there are not many studies for triple-eccentric butterfly valves. Moreover, if the fluid of pipeline flows in the bi-direction then it makes more complicate to adapt triple-eccentric butterfly valves to flow control. In this study, we are trying to develop a bi-directional triple-eccentric butterfly valve through sealing mechanism and stem design study. Digital mockup using 3D CAD was constructed for shape interference check and structural analysis was conducted for structural safety. Also we performed leakage test to check out the durability of the bi-directional pressure for the developed valve.