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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 35, Issue 4 - Nov 1998
Volume 35, Issue 3 - Aug 1998
Volume 35, Issue 2 - May 1998
Volume 35, Issue 1 - Feb 1998
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Vorticity Based Analysis of the Viscous Flow around an Impulsively Started Cylinder
Kwang-Soo Kim ; Jung-Chun Suh ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 1~10
This paper presents a vorticity-based numerical method for analyzing an incompressible Newtonian viscous flow around an impulsively started cylinder. The Navier-Stockes equations have a natural Helmholtz decomposition. The vorticity transport equation and the pressure equation are derived from this decoupled form. The associated boundary conditions are dynamic for the vorticity and pressure variables representing the coupling relation between them and the force balance on the wall. The various numerical treatments for solving the governing equations are introduced. According to Wu et al.(1994), the boundary conditions are decoupled, keeping the dynamic relation between vorticity and pressure. The vorticity transport equation is formulated by FVM and TVD(Total Variation Diminishing) scheme is used for the convection term. An integral approach similar to the panel method is used to obtain the velocity field for a given vorticity field and the pressure field, instead of the conventional differential approaches. In the numerical process, the structured grid is generated. The results are compared to existing numerical and analytic results for the validity of the present method.
Performance Test and Model-Ship Correlation for a Waterjet Propulsion System
Jong-Woo Ahn ; Chang-Yong Lee ; Young-Ha Park ; Jong-Ahn Chung ; Byung-Hyun Kim ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 11~18
This study describes sea trial tests for a waterjet propulsion system attached in the hybrid super high speed cargo ship named "Narae". A measuring technique of jet velocity, gross thrust and impeller torque for the waterjet system is explained. From the measured data in sea trial test, performance of the waterjet propulsion system is analyzed and compared with model test results of a similar waterjet system which was carried out in 1996. The erective horse power estimated from sea trial tests shows a good agreement with resistance test results of the model ship. The optimum rising height is estimated as 0.75 m, and the overall efficiency of the waterjet system is predicted as 0.315 at 15 knots. Useful data such as the pump performance, the jet efficiency, the losses of inlet duct and nozzle were obtained. Test results show a similar behavior to the model test results.
Approximate Technique for Ship′s Manoeuvrabilily Prediction
Ho-Young Lee ; Sang-Sung Shin ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 19~26
In this paper, we studied the Similar Ship(SS) concept[1,2] as a method to an experimental and semi-emperical approach for the estimation of hull hydrodynamic forces and hull-propeller-rudder interaction coefficients and used these methods to predict ship's manoeuvrability. The SS concept is adopted to use experimental data of prototype ships for manoeuvrability prediction of a new ship. The SS concept is composed of the key components as follows: existence of experimental data about prototype ship, availability of semi-emperical method for estimating the changes of hull force, a method to correct the prototype ship data. On the basis of these concepts, we attempted to simulate manoeuvrability at ballast and scantling draft conditions by making use of experimental data at full load draft condition and to simulate manoeuvrability of new ships by making use of experimental data for prototype. From present calculation, it was found that the present method can predict the ship's manoeuvrability accurately at early design stage.
A Study on the Sloshing of Cargo Tanks Including Hydroelastic Effects
Dong-Yeon Lee ; Hang-Shoon Choi ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 27~37
The sloshing is very important in a safe transport of the liquid cargo by a ship. With the increasing number of supertanker and LNG carriers, this problem has become increasingly more important. In order to study the magnitude and characteristics of impact pressures due to sloshing, experiments ware performed with a rectangular tank and compared with numerical results. Structural responses of tank wall under impulsive pressures were measured. Structural vibrations induced by the sloshing load were analysed by including hydroelastic erects in terms of added mass and damping. To check the validity of the numerical model, the natural frequencies of plate in air and water were compared with measurements, and a good agreement was found. In the case that a plate vibrates under impulsive loads, the pressure on the flexible plate is larger than that on the rigid plate without hydroelastic effects, which was confirmed experimentally. The frequency of oscillatory pressure as well as accel%pion coincides with the natural frequency of plate in water.
Stress Intensity Factor Calculation Using the Hybrid Formulation of Boundary and Finite Element Method (1st Report)
In-Sik Nho ; Chae-Whan Rim ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 38~45
It is a tedious and excessive time consuming process to model the local area of crack tip part of structures in calculation of stress intensity factors by FEM. So, in this paper, the hybrid method of FEM and BEM approach was formulated to overcome this type of problems. The multi-domained BEM was adopted to simplify the modelling process of complex geometry and singularity characteristics of crack tip part and the ordinary FEM modelling was used in the rest part. The example calculations shows very good results compared with analytic solutions and other numerical method.
Effect of Notch Geometries on Dynamic Stress Concentration Factor
O.S. Lee ; H.S. Jeon ; K.H. Byun ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 46~54
In this paper, the erect of notch geometries on dynamic stress concentration was investigated by using the dynamic photoelasticity and the drop weight loading system Dynamic stress fields arisen by elastic wave through the loading system around various types of notch geometries were captured by using
frame rate Cranz-Shardin camera system with 12 photographic frames. We found that dynamic stress concentrations around the notch tip and comer were highly dependent on the change in notch geometries. The elders of dynamic stress singularity ware determined with respect to varying geometries of notches and we explained dynamic stress concentration in terms of the orders of dynamic stress singularity.
A Study on the Welding Deformations and Residual Stresses for Circumferential Welded Cylinders
K.Y. Yoo ; D.S. Um ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 55~64
Using blind hole drilling method the residual stresses and welding deflections are measured for the cylindrical shell with various heat inputs and cylinder diameters. As a result, it is verified that the axial and hoop residual stresses which are generated near the weld part of cylinders are increased, as the heat inputs and cylinder diameters are increased. And experimental results show good agreements with those of precedent researchers. In this paper, it is validated that dominant parameters, heat input Q and the dimension of cylinder h/D have some effects on the magnitude and distribution of axial and hoop residual stresses and welding deflections. The empirical equations of residual stresses and welding deflections are made by using multiple linear regression with experimental results.
Relation between Arc Phenomena and Spattering Ratio of Flux Cored Arc Welding with 100%
S.W. Kang ; D.S. Um ; E.S. Oh ; D.S. You ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 65~75
welding with 100%
gas is commonly used because of its cost and efficiency. Arc phenomena and spattering ratio of the
welding are influenced by various factors such as chemical compositions of welding wire, shielding gas, welding condition and welding power source etc.. Spattering ratio is predominantly influenced by the welding condition which determines a droplet transfer rode. In this study, arc phenomena and spattering ratio are investigated by using two type of FCW(titania type, semi-metal type). Then, the welding quality and optimum welding condition can be selected. From this study, the following results ware obtained; 1) In low current range(140A), FCW up to welding voltage(22V) resulted in a typical short circuit transfer, increase of spattering ratio and growth of spatter diameter. 2) In high current range(320A), the arc stability in titania FCW of a typical globular transfer is better than that of semi-metal FCW.
Structural Intensity Analysis of Stiffened Plate Using Assumed Mode Method
Dae-Seung Cho ; Sa-Soo Kim ; Sang-Min Jung ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 76~86
Structural intensity of plates experiencing bending vibration is analytically evaluated using the modal analysis based on assumed mode method. To evaluate the convergence of structural intensity according to the number of superposition modes, the power obtained by structural intensity integration over the closed curve containing the excitation source is compared with the power injected into plates. The erect of power reduction due to the material internal loss is evaluated using the intensity around a localized damping point, In addition, the dominant component among internal forces in the power transfer by the bending vibration of plates and the change of power flow due to stiffener are also investigated.
Development of a High Speed, Coastal Passenger SWATH Ship with Good Speed Performance and Seakeeping Quality
H.H. Chun ; M.S. Kim ; Y.R. Joo ; G.H. Lee ; M.H. Lee ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 87~97
One of good ways to make a ship perform well in rough seas is to reduce its waterplane area and accordingly is subject to a reduced wave exciting forties. However, a great reduction of the waterplane area may create a penalty in speed performance due to the increased ratio of the wetted area to the displacement volume. This paper suggests a new catamaran hull form which compromises the speed and seakeeping quality by increasing the waterplane area somehow compared with that of the conventional SWATH ship. A 350 passenger carrying SWATH ship with a cruising speed of 30 knots in sea state of 4 has been developed and its performance was validated by the model tests. The design concept resistance performance and seakeeping dualities of the design craft are presented together with its comparative performance comparison with other high speed crafts.
Sharing Ship Design Model Based on STEP methodology
Yong-Jae Shin ; Soon-Hung Han ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 98~108
Hull design data is currently prepared by a 2D CAD system and re-input to 3D CAD systems specialized for detail design or to a structural analysis system. In this paper, sharing design data among different CAD systems has been studied. Based on STEP methodology, a neutral model is generated from 2D AutoCAD drawings. To handle a geometric data of this model, the non-manifold model of ACIS is used because it can support various CAD data representation such as 2D graphic entities, 3D wireframe, 3D surface model, and solid B-Rep/CSG model. It is observed that a mon-manifold model can easily be transformed to a 3-D wireframe model for the hull detail design system AutoDef or a FE model for the structural analysis system Nastran.
Generation of Design Candidates and Ship Conceptual Design Assistance by using Case-Based Reasoning
Kyung-Ho Lee ; Dong-Kon Lee ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 109~117
In a preliminary design available information is limited, so it makes attractive to rely on the design cases of existing ships to design new ships. In this paper a prototype of the case-based conceptual design system of a ship is developed to support systematically the design process. This system not only generates design candidates through a case indexing, but also determines the priorities of the candidates by using nearest neighbor matching algorithm. The final solution is presented through adaptation process. The validation of the system was examined and verified by applying to conceptual ship design stage.
Hull Form Representation using a Hybrid Curve Approximation
Hyun-Cheol Kim ; Kyung-Sun Lee ; Soo-Young Kim ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 4, 1998, Pages 118~125
This paper presents the hybrid curve approximation with geometric boundary conditions as position vector and tangent vector of start and end point using a B-spline approximation and a genetic algorithm First, H-spline approximation generates control points to fit B-spline curries through specified data points. Second, these control points are modified by genetic algorithm(with floating point representation) under geometric boundary conditions. This method would be able to execute the efficient design work without fairing.