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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 39, Issue 4 - Nov 2002
Volume 39, Issue 3 - Aug 2002
Volume 39, Issue 2 - May 2002
Volume 39, Issue 1 - Feb 2002
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Simulation for the Propulsion of Micro-Hydro-Machine with Unstructured Grid
Moon-Chan Kim ; Dong-Dai Ha ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 1~7
DOI : 10.3744/SNAK.2002.39.3.001
Flow mechanism of contractive and dilative motion is numerically investigated to obtain a propulsive force in highly viscous fluid, which is the simulation of the propulsion in micro-organisms. The computing code for the analysis of complicated motions is developed with cell-centered unstructured grid scheme. The developed code is validated by the well-known problems of cavity flow and oscillating wall. The validated code is applied to the contractive and dilative motion in narrow tube. The computed results are compared with nodal points scheme. By the present results, it is found that propulsive force can be obtained by the contractive and dilative motion through simulation with the developed code.
Analysis of Open-Water Characteristics of Marine Propeller by Computational Method for Viscous Flow
Dug-Soo Kim ; Hyoung-Tae Kim ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 8~17
DOI : 10.3744/SNAK.2002.39.3.008
In this paper, the computational analysis of open-water characteristics for three model propellers(P4119, P4842 and 3 podded propeller of KRISO) is done by using a viscous-flow method based on Reynolds-Averaged Navier-Stokes equations. The results are presented for open-water performances, blade-section pressures, and circumferentially-averaged velocity profiles for the all three propeller models. Overall close agreements with available experimental data are shown. However, some discrepancies are also found in the pressure near the leading edge of the propeller blade and the open-water performance of the podded propellers.
A Study on a Moving Adaptive Grid Generation Method Using a Level-set Scheme
Il-Ryong Park ; Ho-Hwan Chun ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 18~27
DOI : 10.3744/SNAK.2002.39.3.018
In order to improve the accuracy of the solution near the boundary in an analysis of viscous flow around an arbitrary boundary which move and be deformed using an Eulerian concept, a level-set based grid deformation method is introduced to concentrate grid points near the boundary. This paper presents a new monitor function which can easily control the level of the concentration of grid points along the boundary. Computations for steady flow around a semi-circular cylinder mounted on the bottom of the flow domain were carried out to check the improvement of the solution using the adaptive grid system with an immersed boundary method. The present numerical results show a good agreement with the solutions obtained by a body fitted grid system and more accurate solutions than those computed with non-adaptive grid system. For the validation of mechanical usefulness of the present method, an expanded analysis of flow around multi-body fixed in the flow domain was carried out. Finally, the present moving adaptive grid method was applied to a two-dimensional bubble rise problem. The computed results show well adapted grid points around the boundary of the bubble at every time and a good agreement with the result calculated by fixed grid system.
Numerical Simulation of Turbulent Flow around 2-D Airfoils in Ground Effect
H.H. Chun ; R.H. Chang ; M.S. Shin ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 28~40
DOI : 10.3744/SNAK.2002.39.3.028
Turbulent flows around two-dimensional wing sections in ground effect are analysed by incompressible RANS equations and a finite difference method. The Baldwin-Lomax algebraic turbulence model is used to simulate high Reynolds number flows. The main purpose of this study is to clarify the two-dimensional ground effect and its flow characteristics due to different ground boundary conditions, i.e., moving and fixed bottom boundary. As a first step, to validate the present numerical code, the computational result of Clark-Y(t/C 11.7%) is compared with published numerical results and experimental data. Then, NACA4412 section in ground effect is calculated for various ground clearances with two bottom boundary conditions. According to the computational results, the difference in the lift and moment simulated with the two bottom boundary conditions is negligible, but the drag force simulated by the fixed bottom is to some extent smaller than that by the moving bottom. Therefore, it can be concluded that the drag force measured in a wind tunnel with the fixed bottom could be smaller than that with the moving bottom.
Velocity Field Measurements of Propeller Wake Using a Phase-averaged PTV Technique
Bu-Geun Paik ; Sang-Joon Lee ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 41~47
DOI : 10.3744/SNAK.2002.39.3.041
Turbulent wake behind a ship propeller has been investigated using the adaptive hybrid 2-frame PTV(Particle Tracking Velocimetry). 400 instantaneous velocity fields were measured according to 4 different blade phases and ensemble-averaged to investigate the spatial evolution of the vortical structure of near wake within one propeller diameter downstream. The phase averaged mean velocity fields show the potential wake and the viscous wake formed by the boundary layers developed on the blade surfaces. As the tip vortex evolves downstream, the slipstream is contracted and the turbulent intensity is decreased with viscous dissipation and turbulent diffusion.
PIV Measurements of Wake behind a KRISO 3600TEU Container Ship Model
Sang-Joon Lee ; Min-Seok Koh ; Choung-Mook Lee ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 48~56
DOI : 10.3744/SNAK.2002.39.3.048
The flow characteristics around KRISO 3600TEU container ship model have been experimentally investigated in a circulating water channel. The instantaneous velocity vectors were measured using 2-frame PIV measurement system. The mean velocity fields and turbulent statistics including turbulent kinetic energy and vorticity were obtained by ensemble-averaging 400 instantaneous velocity fields. The free stream velocity was fixed at 0.6m/s and the corresponding Reynolds number was
. The test sections were divided into two regions, three transverse sections of the wake region(Station -0.5767, -1, -3) and five longitudinal sections of the wake((Z/(B/2)=0, 0.1, 0.2, 0.4, 0.6). In the wake region, large-scale longitudinal vortices of nearly same strength are symmetric with respect to the wake centerline and a relatively weak secondary vortex is formed near the waterline. With going downstream, the strength of longitudinal vortex is decreased and the wake region expands.
Dynamic Position Control Method for the Buffer Unit of a Deepsea Mining System
Ki-Hun Kim ; Hang-S. Choi ; Sup Hong ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 57~63
DOI : 10.3744/SNAK.2002.39.3.057
This paper describes a control algorithm for the buffer of a deep-sea mining system, in which the buffer is connected to a long slender pipe and then to a surface ship on one end, and to a collector on sea floor through a flexible hose on the other end. A mathematical modeling is established for designing the controller for buffer thrusters, in which the dynamic response of the long pipe is taken into account based on the mode superposition method. The fluid loading acting on the pipe is estimated by using Morison's formula. For simplicity, the surface ship is assumed to be kept stationary, the reaction from the flexible hose is ignored and only the lateral motions are considered. In order to guide the buffer to react only to the low-frequency motion of the surface vessel, the FIR digital filter is introduced to a PID-based controller It can be shown numerically that the high frequency component of the ship's motion can be effectively filtered out by using the FIR low pass filter.
A Development of Whipping Analysis Program for Ship Hulls
Seong-Whan Park ; Jai-Kyung Lee ; Sang-Heon Oh ; Myung-Jae Song ; Seung-Min Kwon ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 64~74
DOI : 10.3744/SNAK.2002.39.3.064
A special purposed program for ship hull strength analysis considering whipping phenomena is developed. In this program, the non-linear hydrodynamic impact force is considered using the momentum slamming theory and the hull girder is modeled as elastic body on the base of Timoshenko's beam theory. The numerical verifications are conducted in the view points that the effect of slamming impact force, the effect of hydro-elastic formulation, and the effect of various design parameters such as ship speed, wave amplitude, wave length and others. By the application of a real ship design process, the availability of the program is proved. This program has a GUI function for many I/O data process as well as the function to show the 2-D ship motion in the graphic window, and has other available functions for the whipping analysis.
Forming Shop Analysis with Adaptive Systems Approach
Dong-Hun Shin ; Jong-Hun Woo ; Jang-Hyun Lee ; Jong-Gye Shin ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 75~80
DOI : 10.3744/SNAK.2002.39.3.075
In these days of severe struggle for existence, the world has changed a great deal to global and digital oriented period. The enterprises try to introduce new management and production system to adapt such a change. But, if the only new technologies are applied to an enterprise without definite analysis about manufacturing, failure fellows as a logical consequence. Hence, enterprise must analyze manufacturing system definitely and needs new methodologies to mitigate risk. This study suggests that the new approach, which is systems approach for process improvement, is organized to systems analysis, systems diagnosis, and systems verification. Systems analysis analyzes manufacturing systems with object-oriented methodology-UML(Unified Modeling language) from a point of product, process, and resource view. Systems diagnosis identifies the constraints to optimize the system through scientific management or TOC(Theory of constraints). Systems verification shows the solution with virtual manufacturing technique applied to the core problem which emerged from systems diagnosis. This research shows the artifacts to improve the productivity with the above methodology applied to forming shop. UML provides the definite tool for analysis and re-usability to adapt itself to environment easily. The logical tree of TOC represents logical tool to optimize the forming shop. Discrete event simulator-QUEST suggests the tool for making a decision to verify the optimized forming shop.
Distribution of Welding Residual Stresses in T-joint Weld with Root Gap
H.S. Bang ; S.H. Kim ; Y.P. Kim ; C.W. Lee ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 3, 2002, Pages 81~88
DOI : 10.3744/SNAK.2002.39.3.081
The root joint in the welding structures are apt to failure by the stress concentration which is occurred by the external force. Therefore, in the safety and reliability of structure, the complete penetration joint welding which are obtained by the groove welding with edge preparation is generally required. Nevertheless, fillet T-joint welding without edge preparation is often carried out in the fields to reduce working time and consumption of welding electrode, however, this process is likely to produce inadequate joint penetration such as root gap. In this paper, the focus of research is to investigate distribution of welding residual stresses in the plate(or flange) and web of T-joint weld, and especially in the near of root gap notch that is due to incomplete joint penetration. For the analysis, we have chosen model of T-joint weld in the cases of single and multi-pass welding with submerged arc welding and analyzed model by using finite element programs considering the heat conduction and thermal elasto-plastic theory.