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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 30, Issue 4 - Nov 1993
Volume 30, Issue 3 - Aug 1993
Volume 30, Issue 2 - May 1993
Volume 30, Issue 1 - Feb 1993
Selecting the target year
Primitive Instancing for the Definition of Non-conventional Hull
Won-Don Kim ; Jong-Ho Nam ; Kwang-Wook Kim ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 1~9
Various geometric modeling techniques for a hull have been developed with wide application of computer to the ship design. Up to now, they are used for the representation of the sculptured surface with the piecewise polynominal curves or surfaces for a conventional hull. In this paper, a convenient and accurate modeling technique that is instancing and blending of the geometry primitives is introduced for a non-conventional hull such as SWATH, trimaran, caisson etc. Geometric characteristics, hydrostatic particulars and stability of the definded hull are calculated.
Economic Evaluation Method for Marine Electric Generating Systems Using a Comprehensive Economic Index
Jeong-Je Kim ; Seung-Taek Chang ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 10~19
Design optimisation generally necessitates a tool of assessing the economics of designs. This paper proposes a method of assessing the economics of marine electric generating systems. The pay back period(PBP) and the net present valuve(NPV) of the investment for a designed project are properly converted into a economic index. The mechanical factors dominating the easiness in operating the system are also assessed and quantified to form a index which eventually is added to the economic index producing a comprehensive economic index. The method has been tested on a design example and it's validity has been shown.
Optimization of Ship Propulsion System by Hull-Propeller-Engine Interaction
Sung-Soo Ahn ; Chang-Sup Lee ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 20~29
In this paper, a procedure is presented to optimize ship propulsion systems considering the hull- propeller-engine interactions. The propeller diameter and expanded blade ratio are systematically varied to find out the optimum combinations of RPM and BHP at a given design speed by considering cavitation criteria, and then by comparing the fuel oil consumptions of each main engine candidates which can produce each combination of RPM and BHP, appropriate main engine with the lowest fuel oil consumption together with principal characteristics of the optimum propeller are selected.
A Study on the Asymmetric Preswirl Stator System
Moon-Chan Kim ; Jin-Tae Lee ; Jung-Chun Suh ; Ho-Chung Kim ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 30~44
This paper deals with both experimental and theoretical methods for performance prediction of asymmetric stater propulsion systems which have been used for the purpose of recovery of a propeller slipstream rotational energy due to a stator located in front of the propeller. Using the developed computer code based on the lifting surface theory, theortical investigation on the interaction between the stator and the propeller is provided in order to obtain general insight on the performance characteristics of the propulsion systems in uniform and non-uniform flow. Such theoretical calculations have end agreements with model Inset results. The asymmetric stator would give an efficiency gain of about 6% to the compound propulsor system compared with the single propeller system.
The Nonlinear Motions of Cylinders(II) - Translating and Heaving Problem, Body Motion in Waves -
H.Y. Lee ; J.H. Hwang ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 45~64
This paper dealt with the application of a numerical method developed by the authors using the matching method proposed in the previous paper on "The Nonlinear motions of cylinders(I)", and Cauchy's theorem to the problems associated with hydrodynamic forces acting on a heaving cylinders translating in a calm water and also motions of cylinders in waves. In spectral method. body boundary condition in submerged case is satisfied exactly but one in floating case is not satisfied exactly. In the numerical code developed here, the boundary condition at the free-surface and body surface is satisfied exactly at its instaneous position. It is of interest to note that the present scheme could be applied to a free-surface-piercing body without experiencing a difficulty in the numerical convergence. The computed results are compared with other results(, ).
A Numerical Method for Nonlinear Wave-Making Phenomena
Jang-Whan Kim ; Kwang-June Bai ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 65~72
A numerical method for nonlinear free-surface-wave problem is developed in this paper. The final goal of this study is to simulate the towing tank experiment of a ship model and to partially replace the experiment by the numerical model. The exact problem in the scope of potential flow theory is formulated by a variational principle based on the classical Hamilton's principle. A localized finite element method is used in the present numerical computations which made use of the following two notable steps. The first step is an efficient treatment of the numerical radiation condition by using the intermediate nonlinear-to-linear transition buffer subdomain between the fully nonlinear and linear subdomains. The second is the use of a modal analysis in the final stage of the solution procedures, which enables us to reduce the computation time drastically. With these improvements the present method can treat a much larger computational domain than that was possible previously. A pressure patch on the free surface was chosen as an example. From the present computed results we could investigate the effect of nonlinearity on the down-stream wave pattern more clearly than others, because much larger computational domain was treated. We found, specifically, the widening of the Kelvin angle and the increase of the wave numbers and the magnitude of wave profiles.
Prediction of Steady Performance of a Propeller by Using a Potential-Based Panel Method
Young-Gi Kim ; Jin-Tae Lee ; Chang-Sup ; Lee ; Jung-Chun Suh ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 73~86
This paper describes a potential-based panel method for the prediction of steday performance of a marine propeller operating in a uniform oncoming flow. An integral equation with unknown dipole strengths is formulated by distributing the normal dipoles and/or sources on the blade and hub surfaces and the wake sheet, and is solved numerically upon discretization. A hyperboloidal panel has been adopted to compute the potential induced by a normal dipole on a non-planar quadrilateral panel. The Kutta condition is satisfied by iteratively annulling the pressure jumps at the trailing edge. Extensive convergence tests are carried out, and the influence of the wake model upon performance is studied. Predicted performance is shown to correlate well with the experiments.
Wave Responses and Ship Motions in a Harbor Excited by Long Waves(II)
I.H. Cho ; Hang-S. Choi ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 87~93
The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Experiments are performed in a shallow basin. A ship model is set moored by soft springs at various positions in a model harbor subjected to regular waves with period ranging from 2 to 3 seconds. Wave and ship responses are measured and compared with theory. It is found that theoretical results agree qualitatively with experimental results. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.
Study on the Flow Around an Elliptic Wing Using Flow Visualization Technique
Beom-Soo Hyun ; Moon-Chan Kim ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 94~103
This study deals with an investigation on the tip vortex generated by an elliptic wing with section shapes of NACA 0020. The flow structure on the wing surface is investigated by using tufts test as well as observing the cavitation pattern. The surface pressure on a foil surface is measured to complement the visualized flow field. Results show that a strong spanwise pressure gradient is a definite contributor on the formation of tip vorex, and the fluids from both sides contribute to the evolutionary process of tip vortex. On the other hand, a series of experiments are conducted to investigate the detailed structure of tip-vortex at various angles of attack. The tip-vortex formation and development are observed by producing a cavitation, and then by a laser sheet technique in conduction with a dye injection method. The shape of tip-vortex and the distance between a vortex core and the trailing vortex sheet are found to vary with the angle of attack. Overall features of tip flow are evaluated to complement the vortex model based on inviscid theory.
Numerical Simulation of Laminar Flows for a Circular Cylinder Vertically Piercing Free Surface
Bum-Sang Yoon ; Yoon-Ho Kim ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 104~114
In this paper, effects of free surface on viscous flow is investigated. Continuity equation coupled with Navier-Stokes equations are solved numerically by using an artificial compressibility method[1, 2]. The body-fitted generalized curvilinear coordinate system is employed to deal with arbitrary body shape. The IAF scheme with finite difference method is used to solve the equations, and a diagonal algorithm is applied to time-varying Jacobian matrices for the computational economics. Free surface shape is obtained by applying zero pressure condition to still water surface at each time step. A numerical test is made for larminar flow around a circular cylinder vertically piercing the free surface. Computed flow patterns are largely affected by the existance of free surface in low Reynolds number flows treated in this paper. Free surface causes viscous pressure drag to vary much in depth direction in accordance with the variations of flow pattern.
System Reliability Analysis of Midship Sections
Y.S. Yang ; Y.S. Suh ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 115~124
A structural system reliability analysis is studied for the safety assessment of midship section. Probabilistically dominant collapse modes are generated by Element Replacement Method and Incrimental Load Method. In order to avoid generating the same modes repeatedly, it is branched at final plastic hinge. Using first and second order bound methods, system failure probability of midship section is computed and compared with deterministic load factor method to show the usefulness of the proposed method.
Vibration and Dynamic Sensitivity Analysis of a Timoshenko Beam-Column with Ends Elastically Restrained and Intermediate Constraints
J.H. Chung ; W.H. Joo ; K.C. Kim ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 125~133
Most studies on the vibration analysis of a beam-column with ends elastically restrained and various intermediate constraints have been based on the Euler beam theory, which is inadequate for beam-columns of low slenderness ratios. In this paper, analytical methods for vibration and dynamic sensitivity of a Timoshenko beam-column with ends elastically restrained and various intermediate constraints are presented. Firstly, an exact solution method is shown. Since the exact method requires considerable computational effort, a Rayleigh-Ritz analysis is also investigated. In the latter two kinds of trial functions are examined for comparisions : eigenfunctions of the base system(the system without intermediate constraints) and polynomials having properties corresponding to the eigenfunctions of the base system. The results of some numerical Investigations show that the Rayleigh-Ritz analysis using the characteristic polynomials is competitive with the exact solutions in accuracy, and that it is much more efficient in computations than using the eigenfunctions of the base system, especially in the dynamic sensitivity analysis. In addition, the prediction of the changes of natural frequencies due to the changes of design variables based on the first order sensitivity is in good agreements with that by the ordinary reanalysis as long as the changes of design variables are moderate.
Vibration Analysis of the Sandwich Plates with very thin faces
In-Kyu Park ; Ik-Tai Kim ; Choong-Yul Son ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 134~144
Sandwich plate is consisted of equal two isotropic, thin, stiff and strong sheets of dense material separated symmetrically by an isotropic thick layer which may be much less stiff and strong. This study analyzed the dependency of the natural frequencies and mode shapes of sandwich plates on material properties, thicknesses of faces and cores, and various boundary conditions using Rayleigh-Ritz method. E-glass Woven Roving and another two kinds of materials were selected as a face, P.V.C. and another kinds of materials were selected as a core. Natural frequencies and mode shapes obtained by Rayleigh-Ritz method were compared with F.E.M. solutions using ADINA program.
Finite Element Analysis for Plastic Large Deformation and Anisotropic Damage
I.S. Nho ; S.J. Yim ;
Journal of the Society of Naval Architects of Korea, volume 30, issue 1, 1993, Pages 145~156
An improved analysis model for material nonlinearity induced by elasto-plastic deformation and damage including large strain response was proposed. The elasto-plastic-damage constitutive model based on the continuum damage mechanics approach was adopted to overcome limitations of the conventional plastic theory, which can manage the anisotropic tonsorial damages evolved during time-independent plastic deformation process of materials. Updated Lagrangian finite element formulation for elasto-plastic damage coupling problem including large deformation, large rotation and large strain problems was completed to develop a numerical model which can predict all kinds of structural nonlinearities and damage rationally. Finally, a finite element analysis code for the 2-dimensional plane problem was developed and the applicability and validity of the numerical model was investigated through some numerial examples. Calculations showed reasonable results in both geometrical nonlinear problem due to large deformation and material nonlinearity including the damage effect.