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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
Journal Basic Information
Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 36, Issue 4 - Nov 1999
Volume 36, Issue 3 - Aug 1999
Volume 36, Issue 2 - May 1999
Volume 36, Issue 1 - Feb 1999
Selecting the target year
Numerical Study of the Flow Field Around an Axisymmetric Body with Integrated Propulsors
Jong-Woo Ahn ; Il-Sung Moon ; Sang-Woo Pyo ; Jung-Chun Suh ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 1~8
Numerical study is carried out to investigate flow characteristics around an axisymmetric body with and without an integrated propulsor. The incompressible Reynolds-Averaged Navier-Stokes(RANS) equations are also solved using the finite volume method and the standard
turbulence model for turbulence closure. In order to investigate the propulsor-hull interaction, the induced velocity calculated by surface panel methods is utilized for the boundary condition at the propeller plane. The calculated results are compared to the experimental results. It is considered that the present numerical code can be used for design of an integrated propulsor.
Analysis of Two-dimensional Hydrofoil Problems Using Higher Order Panel Method based on B-Splines
Chung-Ho Cho ; Gun-Do Kim ; Chang-Sup Lee ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 9~20
A higher order panel method based on B-spline representation for both the geometry and the velocity potential is developed for the solution of the flow around two-dimensional lifting bodies. The self-influence functions due to the normal dipole and the source are separated into the singular and nonsingular parts, and then the former is integrated analytically whereas the latter is integrated using Gaussian quadrature. A null pressure jump Kutta condition at the trailing edge is found to be effective in stabilizing the solution process and in predicting the correct solution. Numerical experiments indicate that the present method is robust and predicts the pressure distribution around lifting foils with much fewer panels than existing low order panel methods.
Analysis on the Flow Field Around a Hydrofoil with Surface Blowing
Sang-Woo Pyo ; Jung-Chun Suh ; Hyo-Chul Kim ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 21~27
A low order panel method based on the perturbation potential is applied for prediction of performance of blown-flap rudders. In order to improve the solution behavior at the large angle of attacks, the geometry of the trailing wake sheet is computed by aligning freely with the local flow. The effect of the wake sheet roll-up is also included with use of a high order panel method. The flow in the gap between the main component and the flap of the rudder is modeled as Couette flow. The effects of the gap and the flow jet are included in application of a kinematic and a dynamic boundary condition on the inlet and the outlet of the gap as well as on the flap and the wake. The results with the present method are compared with existing experimental data. The method is shown to be capable of determining accurately the flow characteristics even for large flap angles.
The Inverse Design Technique of Propeller Blade Sections Using the Modified Garabedian-McFadden Method
C.M. Jung ; J.K. Cho ; W.G. Park ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 28~36
An efficient inverse design method based on the MGM(Modified Garabedian-McFadden) method has been developed. The 2-D Navier-Stokes equations are solved for obtaining the surface pressure distributions and coupled with the MGM method to perform the inverse design. The MGM method is a residual-correction technique, in which the residuals are the difference between the desired and the computed pressure distribution. The developed code was applied to several airfoil shapes and the propeller. It has been found that they are well converged to their targeting shapes.
Analysis of Flow Around A Rigid Body on Water-Entry & Exit Problems
Il-Ryong Park ; Ho-Hwan Chun ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 37~47
A Finite Volume Method for the discretization of the two-dimensional incompressible Navier-Stokes equation is used to analyse water entry & exit problems in a generalized coordinate system. The free-surface deformations generated by the water entry or exit of a rigid body are simulated by the Level-Set scheme. In the water entry problems for a wedged section and a flared-ship section, the calculation results of water impact force are compared with the experimental results and the time varying free-surface deformations and flow characteristics of the water exit of a cylinder are investigated.
A Study on the Ill-posed Inverse Problem of Two-dimensional Waves due to Pressure Distribution Using Regularization Method
Taek-S. Jang ; Hang-S. Choi ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 48~55
In this paper, the ill-posed inverse problem of surface waves caused by a two-dimensional pulsating pressure distribution on the free surface is studied using the regularization method. In order to exemplify the method, a cosine pressure distribution on a limited range of the undisturbed free surface is considered. By taking the resulting horizontal velocity as input data, the corresponding pressure is determined numerically by three different regularization schemes. It is found that the iterated Tikhonov method provides with the most accurate result, while solutions obtained from the Landweber-Friedman regularization are most stable.
Resistance and Seakeeping Tests of a LOA 47.7m Class Catamaran
H.H. Chun ; Y.K. Chung ; S.S. Chung ; R.H. Chang ; S.W. Ha ; J.M. Kim ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 56~63
The seakeeping and resistance tests of a 47.7m class catamaran are conducted in a towing tank with the 1/21.5 scale model. The effect of the trim tab on the resistance is investigated with the trim tab angle variations and the resistance and trim angle of the catamaran with the trim tab are compared with those without the trim tab. The heave and pitch motions are measured at the three full scale speeds in sea state of 3.4 and 5 and the vertical accelerations at five points on the deck are also measured. The measured accelerations are compared with the criteria of ISO 2631/3 and it is shown that the seakeeping performance of the catamaran is good.
A Study on the Development of Hydroelastic Experimental Techniques of Very Large Box-shaped Floating Structures with Shallow Draft
H. Shin ; I.K. Park ; H.S. Shin ; S.K. Kim ; Y.S. Yang ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 64~76
In this paper hydroelastic experimental techniques of very large floating offshore structures are suggested based on the model test carried out in the UOU Ocean Engineering Wide Tank. The prototype is a box-shaped floating structure with length of 300m, breadth of 60m, depth of 2m and draft of 0.5m and longitudinal bending rigidity as
. The scale ratio is 1/42.857. The model is realized by aluminum square pipes with the section dimension of
. The numbers of longitudinal and transverse pipes are 7 and 35 respectively. Heave motions at selected points are measured with potentiometers and bending moments with strain gages.
Development of Structural Analysis System of Bow Flare Structure(1) - Prediction of Wave Impact Load Characteristics -
S.G. Lee ; M.S. Kim ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 77~86
The bow flare structure of a ship is designed considering wave impact loads largely caused by relative motion of the ship and wave at rough sea. Empirical design is still used because impact phenomenon and structural behaviour due to wave impact load can not examined accurately. The objective of this study is, as the first step, to predict wave impact loads giving the structural damages to the bow flare structure from the damage data inversely, using dynamic nonlinear finite element code LS/DYNA3D, and to perform various parametric studies of wave impact pressure curve for its characteristics, such as peak height, duration time, tail height, rise time, etc.. The followings were obtained from this study: Dynamic structural responses against wave impact loads are largely affected by impact pressure impulse whose amount during duration time until peak deformation is very important.
Development of Structural Analysis System of Bow Flare Structure(2) - Prediction of Wave Impact Load Area -
S.G. Lee ; J.W. Park ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 87~94
Empirical design is still used to avoid a structural damage because impact phenomenon and structural behaviour due to wave impact load can not examined accurately. The damage due to wave impact load is largely affected by impact pressure impulse and impact load area. The objective of this study is, as the second step, to develop an efficient scantling program of bow flare structure, and to predict its impact load area by comparing maximum dented deformations at center of idealized panel structure model of bow flare structure of 300k DWT VLCC using LS/DYNA3D code, which will be used for its verification of dynamic structural analysis, as the next step. Through this study, the impact load area was estimated as
stiffener space(s) in the case of panel with stiffeners and as
, with stringers, under impact pressure curve with peak height 6.5MPa, tail height 1.0MPa, and duration time 5.0msec.
A Study of Lamella Tearing being Produced by Corner Joint Welding in Box Column of Ultra Thick Plate
Han-Sur Bang ; Seong-Joo Kim ; Jong-Myung Kim ; Woong-Sung Jang ; Young-Seob Kwon ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 95~104
Use of the ultra thick plate is being continuously increased in large off-shore structures, ships, bridges and skyscraper construction, due to increasingly large-sized steel structures and it seems that this trend will be maintained. But, occurrence of the lamella tearing has been reported in ultra thick plate used for construction. It is reportedly caused by impurities such S(sulfur), P(phosphorus) and others accumulated in the ultra thick plate's centerline in the thickness direction with strip shape or by restraint residual stress caused by the welding. In the ultra thick plate made by continuous casting method, occurrence of lamination is difficult to avoid because of the properties of production procedure. Therefore, with a view to reducing the lamella properties, this report tries tearing in the steel structure in the view of welding strength rather than metallic properties, this report tries to seek the optimum groove and welding procedure by using the computer simulation based on FEM(Finite Element Method).
A Study on the Hull Form Design System on the Basis of the Associative Geometry Objects
Young-Bok Choi ; Kyu-Yeul Lee ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 105~115
To develope the best optimized hull form, it has been generalized to evaluate the preliminary hull forms with the CFD tools in the initial stage of development and for this process it is needed to prepare various competent hull forms with high degree of fairness. In this paper, a modified shape variation method was developed to maintain the shape and fairness of parent hull form and the automatic update procedure was implemented on the basis of the association concept. It was shown that the hull form of the high quality in fairness and shape inherited from the parent hull form can be archived.
Realtime Simulation of Deformation due to Line Heating for Automatic Hull Forming System
Dae-Eun Ko ; Chang-Doo Jang ; Seung-Il Seo ; Hae-Woo Lee ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 116~127
Line heating is a method widely used in forming ship hull surface. From the viewpoint of mechanics it is large deformation thermal elasto-plastic problem of arbitrary shaped plate. Many researches have been carried out to resolve this problem. Especially, Jang et al. proposed a simplified thermal elasto-plastic analysis method to predict effectively the deformation of plate due to line heating. In this paper, we improved the method of Jang et al. by considering tension yielding in temperature decreasing stage and verified with experimental results. FEA program using MITC4 degenerated shell element was made to deal with elastic large deformation problem. The newly proposed method can be used in the simulation and control of forming hull surface for higher productivity with simplicity and efficiency.
Simulation Based Design of an Automated Hull-piece Manufactruing System
S.J. Sohn ; J.G. Shin ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 128~136
This paper suggests a new object-oriented methodology, ESBD(Evolutionary Simulation Based Design), for the development of an automated manufacturing system in shipbuilding. The target system, AHMS(Automated Hull-piece Manufacturing System), is a virtualized and distributed system controlling the manufacturing processes of storing, surface-pretreatment, cutting, 1st and 2nd curvature generation of material plates. The control and product-flow simulation is applied for the real-time product monitoring and product data management(PDM). The prototype system of AHMS also outlines the layout of the new automated factory.
Optimization for Inspecdtion Planning of Ship Structures Considering Corrosion Effects
Sung-Chan Kim ; Jang-Ho Yoon ; Yukio Fujimoto ;
Journal of the Society of Naval Architects of Korea, volume 36, issue 4, 1999, Pages 137~146
Inspection becomes to be important in the safety of structure and economical viewpoint, because structural damage accompanies lots of economical cost and social problems. Especially ship structure is composed of a lot of members and it is impossible to inspect all members continuously. The purpose of this paper is to get optimal inspection plan containing inspection time and method. Crack is one of major modes on the structural failure and can lead to collapse of structure. In this paper, the deteriorating process, which contains inspection to detect the crack before the propagation to large crack, is idealized as Markov chain model. Genetic algorithm is also used to accomplish the optimization of inspection plan. Especially, the probabilistic characteristics of cracks are changed, because ship is operating in corrosive environments and the scantling of structural members is reduced due to corrosion. Non-stationary Markov chain model is used to represent the process of corrosion in structural members. In this paper, the characteristics of indivisual inspection plan are compared by numerical examples for the change of corrosion rate, the cost due to scheduled system down and target failure probability. From the numerical example, it can be seen that the improvement of fatigue life for the members with short fatigue life is the most effective way in order to reduce total maintenance cost.