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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 48, Issue 6 - Dec 2011
Volume 48, Issue 5 - Oct 2011
Volume 48, Issue 4 - Aug 2011
Volume 48, Issue 3 - Jun 2011
Volume 48, Issue 2 - Apr 2011
Volume 48, Issue 1 - Feb 2011
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Comparison Study and Structural Analysis to Investigate the Design Rule and Criteria of Catamaran
Kim, Byung-Jong ; Kwon, Soo-Yeon ; Kim, Sung-Chan ; Lee, Jang-Hyun ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 479~489
DOI : 10.3744/SNAK.2011.48.6.479
Leisure boat and yacht should be designed to meet the domestic regulation and international standards as large merchant vessels do. Recently, each countries are encouraged to follow the regulation of International standards organization. Furthermore domestic organization has not yet announced the design rule and regulation for FRP-catamaran yacht design. Therefore, it has been required to make the regulation for domestic situations of FRP-catamaran. This study deals with the structural strength evaluation of 50ft catamaran by using finite element analysis. Design load of the regulation of International standards organization are compared with the regulation of Korea Register of shipping and Lloyd`s Register.
The Current Situation of the Digital Interface International Standards and an Analysis of Integration Condition of Ships
Park, Jong-Won ; Lim, Yong-Kon ; Yun, Chang-Ho ; Kim, Ok-Soo ; Lee, Jung-Woo ; Chung, Han-Na ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 490~500
DOI : 10.3744/SNAK.2011.48.6.490
The paradigm that ships are navigated by means of analog navigation devices and caption`s experiences is shifted to that ships can be navigated by digital and autonomous navigation systems due to the rapid development of electronics and communication technologies. Hence, all systems deployed in a ship are automated and integrated since corresponding ship systems are not individually operated but integrated and managed under common operating system. In this paper, we overview recent research projects targeted for digitally integrated ships (referred to as digital ships), outline IEC 61162 series, specifying digital interface standards for digital ships, and finally present several issues for further improvement of the IEC 61162 series. In addition, we broadly categorize digital ships into three systems consisting of multiple sub-systems, including a navigation system, a power system, and a automation system in the aspect of operation and function. Corresponding interfacing range and method, as well as interface specification and data types of one system in a digital ship are also described according to sub-systems, respectively.
Numerical Analysis of a Tip Vortex Flow for Propeller Tip Shapes
Park, Sun-Ho ; Seo, Jeong-Hwa ; Kim, Dong-Hwan ; Rhee, Shin-Hyung ; Kim, Ki-Sup ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 501~508
DOI : 10.3744/SNAK.2011.48.6.501
In order to control the tip vortex cavitation occurring around the tip of a rotating propeller blade, researches on the propeller cavitation and blade tip vortex flows have been increased. In this paper, the propeller tip vortex flow for a blunt and sharp tips was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. In numerical open water test, torques, thrusts, pressure distributions and vortex flows were compared for various rotating speeds. To consider a hull wake, the nominal wake was specified in inlet boundary condition. Pressure distributions and vortex flows with the hull wake were investigated for various propeller rotating angles. From the results, it was confirmed that the blunt tip propeller delayed the tip vortex flow.
Study on Effect of Shell Plate Deformation to Radar Cross Section of Warship
Kim, Kook-Hyun ; Cho, Dae-Seung ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 509~515
DOI : 10.3744/SNAK.2011.48.6.509
The radar cross section (RCS) of warships is a crucial design factor to improve the survivability in terms of not only low observablity of the platform but also efficiency of on-board sensors and jamming devices against enemy threat. In design stage, numerical models are generated in order to quantitatively assess RCS, of which hull surfaces are modeled with the finite number of the flat plate. However, in practice, hull surfaces are permanently deformed by various kinds of loads such as winds and ocean waves faced during operations. In this paper, the effect of these shell plate deformation to RCS is numerically investigated. For this purpose, RCS calculations are carried out for various kinds of numerical models, such as single plates, dihedrals, large-sized undulate plates, and virtual warships, with some extent of permanent deformation. The results are compared with those of corresponding models without permanent deformation. It is concluded that the permanent deformation of hull surface highly influences RCS characteristics of warships, therefore they should be considered in the RCS analysis.
Effects on Nonlinear Ship Motions on Ship Maneuvering in Large Amplitude Waves
Seo, Min-Guk ; Kim, Yong-Hwan ; Kim, Kyong-Hwan ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 516~527
DOI : 10.3744/SNAK.2011.48.6.516
This paper considers a numerical analysis of ship maneuvering performance in the high amplitude incident waves by adopting linear and nonlinear ship motion analysis. A time-domain ship motion program is developed to solve the wave-body interaction problem with the ship slip speed and rotation, and it is coupled with a modular type 4-DOF maneuvering problem. Nonlinear Froude-Krylov and restoring forces are included to consider weakly nonlinear ship motion. The developed method is applied to observe the nonlinear ship motion and planar trajectories in maneuvering test in the presence of incident waves. The comparisons are made for S-175 containership with existing experimental data. The nonlinear computation results show a fair agreement of overall tendency in maneuvering performance. In addition, maneuvering performances with respect to wave slope is predicted and reasonable results are observed.
Mechanical Bending Process and Application for a Large Curved Shell Plate by Multiple Point Press Machine
Hwang, Se-Yun ; Lee, Jang-Hyun ; Ryu, Cheol-Ho ; Han, Myung-Soo ; Kim, Kwang-Ho ; Kim, Kwang-Sik ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 528~538
DOI : 10.3744/SNAK.2011.48.6.528
As a forming method for curved hull plates more efficient than the flame bending, mechanical bending using multi point press forming and die-less forming is discussed in this paper. the mechanical forming is a flexible manufacturing system for automatically forming of hull parts. It is especially suited to varied curved parts. This paper discusses a multiple point pressing machine composed of a pair of reconfigurable punches in order to achieve the rapid forming of curved hull plates using division forming and presents how forming information is obtained from the given design surface. Although the mechanical forming can be efficient in the metal forming, spring back after pressing is a phenomenon which must be carefully considered when quantifying the process variables. If the spring back is not accurately controlled, the fabricated shell plate cannot meet assembly tolerance. This paper describes the principles to calculate the proper stroke of each punch at the divided areas. the strokes are determined by an iterative process of sequential pressing and spring back compensation from an unfolded flat shape to its given design surface. FEA(finite element analysis) is used to simulate the spring back of the plate and the IDA(iterative displacement adjustment) method adjusts the offset of pressing punches from the deformation results and the design surface. The shape deviations of two surfaces due to spring back are compensated by integrated system using FEA and IDA method. For the practical application, It is aimed to develop an integrated system that can automatically perform the compensation process and calculate strokes of punches of the double sides` reconfigurable multiple-press machine and some experimental results obtained with mechanical bending are presented.
A Study on the Fatigue Strength of Propeller Blades
Nho, In-Sik ; Lee, Chang-Sup ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 539~543
DOI : 10.3744/SNAK.2011.48.6.539
Recently, to reduce the noise and vibration levels of ships, high skewed marine propellers with thinner thickness are adopted widely, however, such propeller design trend causes to reduce the strength of blades. Propeller blades are rotating continuously in irregular wake field of ships. So, it is necessary to examine the strength of them precisely including from a viewpoint of fatigue strength. In present paper, the fatigue strength of propeller blades was investigated. Firstly, fatigue tests for Al Bronze, the representative propeller material, were carried out. The S-N curve was obtained for the assessment of the fatigue crack initiation life. And the material properties C, m for the fatigue crack propagation analysis based on the Paris` equation were derived. For the 2nd stage, the structural responses of propeller blades in irregular ship wake field was carried out using the finite element analysis code. And the fatigue strength of propeller blades were considered based on the calculated stress levels and material characteristics for fatigue strength.
Reduction of Added Resistance by Internal Flow Control in the Moonpool of a Drillship
Choi, Si-Young ; Lee, Young-Gill ; Jeong, Kwang-Leol ; Ha, Yoon-Jin ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 544~551
DOI : 10.3744/SNAK.2011.48.6.544
The internal flows of moonpool usually causes huge added resistance on drillships, and those are very complex to analyze. Therefore, not only experimental approaches but also numerical simulations are required for better investigations when dealing with the hydrodynamic problems of moonpool. In the present research, numerical simulations are used to find out why the resistance increases by moonpool on a running drillship. That is, the three-dimensional numerical simulations and model tests are carried out to examine the characteristics of internal flow and added resistance by changing the section of the moonpool in both longitudinal and transverse directions. Finally, based on the present studies, an optimized shape of the moonpool is suggested, which effectively reduces added resistance, and that is confirmed with three-dimensional numerical simulations and model tests.
Comparisons of Multi Material ALE and Single Material ALE in LS-DYNA for Estimation of Acceleration Response of Free-fall Lifeboat
Bae, Dong-Myung ; Zakki, Ahmad Fauzan ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 552~559
DOI : 10.3744/SNAK.2011.48.6.552
An interest in Arbitrary Lagrangian Eulerian (ALE) finite element methods has been increased due to more accurate responses in Fluid-Structure Interaction(FSI) problems. The multi-material ALE approach was applied to the prediction of the acceleration response of free-fall lifeboat, and its responses were compared to those of the single-material ALE one. It could be found that even though there was no big difference in the simulation responses of two methods, the single-material and multi-material ALE ones, the latter multi-material ALE method showed a little bit more close response to those of experimental results compared to the former single-material ALE one, especially in the x- and z-direction acceleration responses. Through this study, it could be found that several parameters in the ALE algorithms have to be examined more carefully for a good structural safety assessment of FSI problems.
A Study on the Numerical Simulation Method of Two-dimensional Incompressible Fluid Flows using ISPH Method
Kim, Cheol-Ho ; Lee, Young-Gill ; Jeong, Kwang-Leol ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 560~568
DOI : 10.3744/SNAK.2011.48.6.560
In SPH(Smoothed Particle Hydrodynamics) method, the fluid has been assumed that it is weakly compressible to solve the basic equations composed of Navier-Stokes equations and continuity equation. That leads to some drawbacks such as non-physical pressure fluctuations and a restriction as like small time steps in computation. In this study, to improve these problems we assume that the fluid is incompressible and the velocity-pressure coupling problem is solved by a projection method(that is, by ISPH method). The two-dimensional computation results of dam breaking and gravitational wave generation are respectively compared with the results of finite volume method and analytical method to confirm the accuracy of the present numerical computation technique. And, the agreements are comparatively acceptable. Subsequently, the green water simulations of a two-dimensional fixed barge are carried out to inspect the possibility of practical application to ship hydrodynamics, those correspond to one of the violent free surface motions with impact loads. The agreement between the experimental data and the present computational results is also comparatively good.
Effect of Airborne Noise from Ship Machinery on Underwater Noise
Kim, Hyun-Sil ; Kim, Jae-Seung ; Kim, Bong-Ki ; Kim, Sang-Ryul ; Lee, Seong-Hyun ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 569~574
DOI : 10.3744/SNAK.2011.48.6.569
In research vessels or naval ships, airborne noise from machineries such as diesel engine is the major source of underwater noise at low speed. In this paper, effect of engine noise on underwater noise is studied by considering two paths; sound radiation from hull plate and direct airborne noise transmission through hull plate. SEA (Statistical energy analysis) is used to predict hull plate vibration induced by engine noise, where SEA model consists of only two subsystems; engine room air space and hull plate. The pressure level in water is calculated from sound radiation by plate. Engine noise transmission through hull plate is obtained by assuming plane wave propagation in air-limp plate-water system. Two effects are combined and compared to the measurement, where speaker is used as a source in engine room and sound pressure levels in engine room and water are measured. The hydrophone is located 1 m away from the hull plate. It is found below 1000 Hz, prediction overestimates underwater sound pressure level by 5 to 12 dB.
A Study on Anti-Icing Technique for Weather-Tight Door of Ice-Strengthened Vessels
Jeong, Seong-Yeob ; Chun, Eun-Ji ; Cho, Seong-Rak ; Lee, Chun-Ju ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 575~580
DOI : 10.3744/SNAK.2011.48.6.575
Icing problem of ice-strengthened vessels is an important issue when operating in low temperature environment and it can cause damage to deck machineries and emergency equipments. Many ice-strengthened vessels have since been constructed and operated in accordance with the ice class rules such as Det Norske Veritas (DNV), Russian Maritime Register of Shipping (RS), American Bureau of Shipping (ABS) and so on. Therefore winterization is defined as the preparation of a ship for safe operation. In this research, anti-icing performance tests of weather-tight door have been carried out at various temperature conditions(
) in the low temperature cold room facility and then, ambient temperature, specimen temperature, electric current and temperature of heating cable were measured during the test operations. This research describes the construction guidelines of weather-tight door based on anti-icing test results to apply to the full-scale vessels.
Air Compressibility Effect in CFD-based Water Impact Analysis
Tran, Huu Phi ; Ahn, Hyung-Taek ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 6, 2011, Pages 581~591
DOI : 10.3744/SNAK.2011.48.6.581
This paper describes the air compressibility effect in the CFD simulation of water impact load prediction. In order to consider the air compressibility effect, two sets of governing equations are employed, namely the incompressible Navier-stokes equations and compressible Navier-Stokes equations that describe general compressible gas flow. In order to describe violent motion of free surface, volume-of-fluid method is utilized. The role of air compressibility is presented by the comparative study of water impact load obtained from two different air models, i.e. the compressible and incompressible air. For both cases, water is considered as incompressible media. Compressible air model shows oscillatory behavior of pressure on the solid surface that may attribute to the air-cushion effect. Incompressible air model showed no such oscillatory behavior in the pressure history. This study also showed that the CFD simulation can capture the formation of air pockets enclosed by water and solid surface, which may be the location where the air compressibility effect is dominant.