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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 38, Issue 4 - Nov 2001
Volume 38, Issue 3 - Aug 2001
Volume 38, Issue 2 - May 2001
Volume 38, Issue 1 - Feb 2001
Selecting the target year
Computation of Four Quadrant Performance for a Marine Propeller in Open Water
Hyoung-Tae Kim ; Jeong-Jung Kim ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 1~10
A numerical solution method of the incompressible Reynolds-Averaged Navier-Stokes equations is applied for calculating turbulent flows and performances of a marine propeller in open-water, four-quadrant conditions. Computed propeller flows of the model propeller P4381, for which the experimental data of the open-water performances exist, reveal complex viscous-flow characteristics including three-dimensional flow separations in various off-design conditions and also computed propeller thrusts and torques agree quite well with experimental data except some cases for which severe propeller cavitations occurred in the experiment.
Analysis of Propeller-WIG Interaction and Performance in Potential Flow
H.H. Chun ; M.G. Kim ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 11~22
The interaction between forward mounted propeller and wing in ground effect, and its aerodynamic performance are analyzed by potential flow approximation. A Vortex Lattice Method(VLM) for the propeller analysis and a potential based panel method for the WIG are used together with an image method by assuming the free surface as a rigid wall. The interaction of propeller and wing in the proximity of the ground is taken into account by an iterative procedure where the boundary conditions are satisfied with the given convergence criteria. The program developed is first checked by comparing its numerical results with the experimental data and other numerical results for the propeller MP101-rudder MR21 system. Then, the propeller-WIG interaction and its performance versus ground clearance are investigated by changing parameters such as propeller position, diameter and speed of revolution. It is shown that the forward mounted propeller increases the lift forces of the wing and also enhances the height stability, depending on the design parameter. Therefore, the appropriate selection of the design parameter such as propeller diameter, revolution, the longitudinal and vertical position of propeller is necessary.
A Design of Collision Avoidance System of an Underwater Vehicle
Nam-Sun Son ; Key-Pyo Rhee ; Sang-Mu Lee ; Dong-Jin Yeo ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 23~29
An Obstacle Avoidance System(OAS) of Underwater Vehicle(UV) in diving and steering plane is investigated. The concept of Imaginary Reference Line(IRL), which acts as the seabed in the diving plane, is introduced to apply the diving plane avoidance algorithm to the steering plane algorithm. Furthermore, the distance to the obstacle and the slope information of the obstacle are used for more efficient and safer avoidance. As for the control algorithm, the sliding mode controller is adopted to consider the nonlinearity of the equations of motion and to get the robustness of the designed system. To verify the obstacle avoidance ability of the designed system, numerical simulations are carried out on the cases of some presumed three-dimensional obstacles. The effects of the sonar and the clearance factor used in avoidance algorithm are also investigated. Through these, it is found that the designed avoidance system can successfully cope with various obstacles and the detection range of sonar is proven to bea significant parameter to the performance of the avoidance.
Estimation of External Forces and Current Variables in Sea Trial by Using the Estimation-Before-Modeling Method
H.K. Yoon ; K.P. Rhee ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 30~38
The current is considered in the conventional manoeuvering equation. This equation is represented as the nonlinear state and measurement equations in which external forces and the direction and the velocity of current are augmented as that variables. The external forces are modeled as the third-order Gauss-Markov processes and the direction and the velocity of current are assumed to be constant. The augmented state variables are estimated with extended Kalman-Bucy filter and the fixed-interval smoother. While Hwang estimated motion state variables, hydrodynamic coefficients and the current variables simultaneously by using extended Kalman filter, external forces of surge, sway and yaw and the direction and the velocity of current are the only parameters to be estimated in the estimation-before-modeling method. The current variables are satisfactorily estimated in simulation process where the measurement noise is present.
A Time Domain Analysis for Hydroelastic Behavior of a Mat-type Large Floating Structure in Calm Water under Dynamic Loadings by Mode Superposition Method
D.H. Lee ; K.N. Jo ; Y.R. Choi ; S.Y. Hong ; H.S. Choi ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 39~47
In this paper, the hydroelastic behavior of a mat-type large floating structure is analyzed in time domain by using mode superposition method. The time-memory function is estimated by Fourier transforming the wave damping coefficients, which are computed by a higher-order boundary element method based on potential theory. Meanwhile, the structural response is obtained by time integrating the eigenmodes of the structure. Numerical examples are made for three test cases on the scaled model of a mat-type large floating structure ; weight pull-up case, weight drop case and weight moving case. In all three cases, the numerical results coincide well with experimental data.
The Sensitivity Analysis of Coupled Axial and Torsional Undamped Free Vibration of Ship Propulsion Shafting
Yeon-Ho Kim ; Dae-Seung Cho ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 48~55
In this paper, sensitivity analysis for the coupled axial and torsional undamped free vibration of ship propulsion shafting is proposed. The purpose of this study is to effectively and optimally design the resonance frequencies of propulsion shafting affecting barred speed range of main engine by modifying the diameters of intermediate and propeller shafts. The presented method is validated by the sensitivity analysis for the natural frequencies of propulsion shafting of two real large merchant ships. In addition, the changes of natural frequency and resonance main engine speed are discussed in case that the diameter is varied within the range regulated by the rule of shipping register.
Mapping 2D Midship Section into 3D Structural Models based on STEP AP218
Ho-Jin Hwang ; Soon-Hung Han ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 56~65
The structural model of midship section is within the scope of STEP AP218. It supports to represent the ship structure, but most of shipyards and classification societies exchange the information using 2D drawings at the present. To translate the 2D information into the ship structure model of STEP AP218, we analyze the 2D midship section information of KR-TRAS of Korean Register of shipping, and include the transverse members information with the 3D model. We also define the mapping table and the mapping relationships between two data structures. With this mapping table we develop the translator for the midship section, and visualize the translated ship structure model using a STEP viewer. The ship structure model can be used to exchange information between design departments, and through the lifecycle of design, analysis, and maintenance.
Simulation of Plate Deformation by Triangle Heating Process
Chang-Doo Jang ; Dae-Eun Ko ; Sung-Choon Moon ; Yong-Rok Seo ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 66~74
Plate bending process is indispensible in shipbuilding. The process includes press bending process and heating process. Especially the heating process is carried out exclusively by skillful workers. Many researches have been made to automate the heating process. This study was carried out as a fundamental study to develop a efficient analysis method for triangle heating and focused on clarifying the deformation characteristics of plate by triangle heating and essential elements effect on the deformation. In this paper, we proposed an analysis model for thermal-elastic-plastic analysis and simulated the deformation by triangle heating using ANSYS based on the experimental results of Jang et al.(2001). Also, we showed the deformation characteristics more clearly by comparing the deformation due to triangle heating and line heating in case that the total heat input is same. Finally, we investigated the change characteristics of deformation elements according to the volumetric heat input.
Re-distribution of Welding Residual Stress Due to Tensile Pre-load and Its Effects on Fatigue Strength in Padding Plate Weldment
S.W. Kang ; Y.W. Kim ; W.S. Kim ; D.H. Kim ;
Journal of the Society of Naval Architects of Korea, volume 38, issue 4, 2001, Pages 75~82
Static loadings on ship structure induced either by water pressure before service such as a tank test and ballasting or by cargo pressure during first laden voyage cause relatively much greater stress than dynamic loadings induced by wave. With these static pre-loadings, the initial residual stresses around welded joint, where fatigue strength is concerned(in most cases, where stress concentration occurs) are expected to be shaken-down in a great extent by the elasto-plastic deformation behavior of material. Therefore, it is more resonable to assess the fatigue strength of ship structure with S-N data which have taken into account the effect of shaken-down residual stresses(re-distributed stresses) on the fatigue strength. In this research work, the re-distribution of residual stresses by the tensile pre-loading is measured using an ordinary sectioning method for specimens of padding plate weldment. Fatigue tests are performed also to evaluate the fatigue strength of the both as-welded and pre-loaded specimens.