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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 39, Issue 4 - Nov 2002
Volume 39, Issue 3 - Aug 2002
Volume 39, Issue 2 - May 2002
Volume 39, Issue 1 - Feb 2002
Selecting the target year
The Flow Noise Characteristics on Hydrophone Installation Method in the Cavitation Tunnel
J.W. Ahn ; Y.H. Park ; K.S. Kim ; J.T. Lee ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 1~7
DOI : 10.3744/SNAK.2002.39.1.001
As the existing noise measuring device was affected the flow-field and structural vibration directly, new experimental device was required. Two Hydrophone Boxes are designed and their performances are investigated. The noise level of the KRISO cavitation tunnel is compared with those of the other cavitation tunnels which have been designed for the noise study. The present experimental results show the possibility of the full-scale prediction for propeller cavitation noise and the improvement of the measurement performance at the range of low-frequency.
Analysis of Steady Flow Around a Two-Dimensional Body Under the Free Surface Using B-Spline Based Higher Order Panel Method
Jae-Moon Lew ; Yang-Ik Kim ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 8~15
DOI : 10.3744/SNAK.2002.39.1.008
A two-dimensional higher order panel method using B-splines has been developed to overcome the disadvantages of the low order panel method and to obtain more accurate solution. The sources and the normal dipoles are distributed on both the body and the free surface. Instead of applying the upwind finite difference schemes to satisfy the linearized free surface and the radiation condition, the derivatives of the basis functions of the B-splines are directly applied to the linearized free surface condition. Numerical damping in the Dawson's method are avoided in the Present computations. In order to validate the present method, numerical computations are carried out for a submerged cylinder and a two-dimensional hydrofoil steadily moving beneath a free surface. The numerical results show that fast convergence and better accuracies have been achieved by the present method.
Basic Analysis of Bubble Behavior in the Viscous Flow Domain with the Free Interface
I.R. Park ; H.H. Chun ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 16~27
DOI : 10.3744/SNAK.2002.39.1.016
A level-set method is used for analyzing the behaviors of gas bubbles in two fluids incompressible viscous flow domain. The governing equations are solved by using a finite volume method. The numerical results are verified by comparing with the experimental and other computational results. Computations for the deformations and motions of one or multi-bubbles in the flow domain with the initial undisturbed free interface are conducted. It can be seen that numerical results for different surface tension and density ratio arise very different behaviors of bubbles. When bubbles rise near the free interface, the free interface gives some great influence on the behaviors of bubbles. The present results computed by a level-set method give useful information about the properties of bubble motions and deformations.
Nonlinear Dynamic Analysis on Low-Tension Towed Cable by Finite Difference Method
Han-Il Park ; Dong-Ho Jung ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 28~37
DOI : 10.3744/SNAK.2002.39.1.028
In this study nonlinear dynamic behaviors of towed tow-tension cables are numerically analysed. In the case of a taut cable analysis, a bending stiffness term is usually neglected due to its minor effect but it plays an important role in a low-tension cable analysis. A low-tension cable may experience large displacements due to relatively small restoring forces and thus the effects of fluid and geometric non-linearities become predominant. The bending stiffness and non-linearity effects are considered in this work. In order to obtain dynamic behaviors of a towed low-tension cable, three-dimensional nonlinear dynamic equation is described and discretized by employing a finite difference method. An implicit method and Newton-Raphson iteration are adopted for the time integration and nonlinear solutions. For the calculation of huge size of matrices. block tri-diagonal matrix method is applied, which is much faster than the well-known Gauss-Jordan method in two point boundary value problems. Some case studies are carried out and the results of numerical simulations are compared with those of a in-house program of WHOI Cable with good agreements.
Theoretical Study on the Generation of Directional Extreme Waves
Key-Yong Hong ; Shuxue Liu ; Seok-Won Hong ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 38~48
DOI : 10.3744/SNAK.2002.39.1.038
Theoretical development to generate the directional extreme waves in model basin is established based on wave focusing method. The effects of associated parameters, such as the directional range, frequency width, and center frequency, are investigated in terms of wave focusing efficiency. The two different spectral models of constant wave amplitude and constant wave slope are applied to control the wave characteristics. The wave packets simulated by theory are compared with numerical results based on Boussinesq equation and FEM. Both controls of direction and frequency spectrum are essential to focus directional waves effectively. It is noticed that wave focusing ability depends on the frequency bandwidth of spectrum rather than center frequency, and both spectral models with same parameters result in the equivalent efficiency of wave focusing.
Three Dimensional Thermal-Elastic Plastic Analysis of GMAW Considering the Melting of Weld Bead
Jang-Hyun Lee ; Jong-Gye Shin ; Ji-Hoon Kim ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 49~60
DOI : 10.3744/SNAK.2002.39.1.049
Welding is essential in ship production since welding is very popular method for joining two or more metals. However, welding causes residual stress and distortion and these give a bad influence to the structure strength and assembly of ship blocks. Therefore, prediction and treatment of residual stress and distortion is a key to accuracy control in shipyard. In this paper, a computational procedure, based on thermal-elastic-plastic 3-dimensional FEA, has been suggested to simulate butt and fillet welding process. In the simulation process, temperature distribution at each time step is obtained by heat transfer analysis and then thermal deformation analysis is done with obtained temperature distributions to find the residual stress and distortion. In heat transfer analysis, enthalpy method is used to realize phase change at melting temperature. Also element birth and death method is used to simulate adding of weld metal in both heat transfer analysis and thermal elastic plastic analysis. The proposed procedure is verified by related researches and the results show good agreement with those of related researches.
Analysis of Radiative Heat Transfer and Thermal Stress in Flaring System of FPSO
Jang-Hyun Lee ; Jong-Gye Shin ; In-Sik Nho ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 61~72
DOI : 10.3744/SNAK.2002.39.1.061
The flaring system of FPSO burns out the byproduct natural gas. The thermal loading due to radiative heat of flaring gas leads to undesirable thermal-stresses on itself. Nowadays it needs to understand the amount of thermal loading of flaring system since the requirement for the safety of the flaring system. However, few studies have been performed on the thermal environment and radiative heat flux on the FPSO flaring system. Present study suggests a procedure to model the thermal environment and a FEA process to analyze the temperature distribution and thermal stresses of FPSO flaring system. In order to get the temperature distribution, the radiative heat conditions and convective heat conditions are included in the heat transfer analysis. By making the use of temperature obtained through heat transfer analysis, the thermal stress analyses are performed. The results of the present study can be used to design the flaring system and determine the heat shield in the flaring system
A Study on the Evaluation of Vibration Characteristics for Onboard Machinery with Resilient Mountings
Su-Hyun Choi ; Kuk-Su Kim ; Yeon Cho ; Byoung-Gon Kim ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 73~81
DOI : 10.3744/SNAK.2002.39.1.073
This study is performed to evaluate and design the vibration characteristics of the onboard machinery with resilient mountings. To reduce the vibration revel of onboard machinery with resilient mountings, it is important to evaluate and, if necessary modify vibration characteristics of the resilient mountings. In this study we have developed a program to calculate natural frequencies of the machinery with resilient mountings, forced vibration levels due to internal excitation force of the machinery itself and external excitation forces of the main engine and the propeller, and the force and motion transmissibility of the resilient mountings. The developed program can be also applied to optimal design of the resilient mountings for obtaining a target natural frequency and for achieving a minimum forced vibration level at the center of gravity of the machinery.
Determination of Inherent Strain Regions to Estimate Plate Deformation by Line Heating
Chang-Doo Jang ; Yun-Sok Yun ; Dae-Eun Ko ; Sung-Choon Moon ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 82~89
DOI : 10.3744/SNAK.2002.39.1.082
The inherent strain method is known to be very effective in predicting the plate deformation by line heating. Traditionally the inherent strain regions have been determined from the temperature distribution and the phase transformation regions(Ac3) of welding experiments. Since the phenomena of line heating are similar to those of welding, the experimental results under the same welding conditions have been applied directly to line heating analysis. The results cannot, however, reflect the effect of heating pattern and plate thickness. Besides, water-cooling in the actual heating process can alter the steel's phase to martensite and shear plastic deformation occurs during the transformation. In this study, the experimental measurement of temperature distribution was substituted with a transient heat transfer analysis using FEM so that we could obtain the temperature distribution according to heat flux models of the heating pass. In order to consider plastic strains occurring additionally under phase transformation, inherent strain regions were assumed to be limited to the eutectoid temperature(Ac1). Using the regions, plate deformations could be predicted to validate our method and the results were in good agreement with the experimental ones
Fatigue Life Assessment of Ship Structures based on Crack Propagation Analysis -Simplified Prediction Method of Stress Intensity Factors-
C.W. Kim ; I.S. Nho ; D.S. Kim ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 90~99
DOI : 10.3744/SNAK.2002.39.1.090
The prediction of stress intensity factor(SIF) is one of the most important factors to analyse the propagation behavior of cracks in hull structural members. Up to now, however, simplified prediction method of SIF has not yet been established for the cracks experienced in large complex structures. As a first step to predict crack propagation behavior in a ship structure with very large structural redundancies, simplified SIF prediction formulas for various crack shapes were derived based on the results of the stress analysis under a non-crack condition in this study. The adequacy of the proposed method was then verified in comparison with other experimental and analysis results.
A Study on the Optimum Structural Design of Naval Vessels
Seung-Il Seo ; Keon-Ho Son ; Myung-Kyu Park ;
Journal of the Society of Naval Architects of Korea, volume 39, issue 1, 2002, Pages 100~112
DOI : 10.3744/SNAK.2002.39.1.100
Naval vessels are not regulated by the class rules, but by the special regulations. This study introduces the concept and characteristics of the regulations of U.S. Navy which has been the most reliable standards in design of naval vessels in Korea, and intends to help designers to comprehend the effect of each regulation on design results. Also, an optimum structural design method combined with the structural analysis theory is proposed for naval vessels following the regulations of U.S. Navy and is applied to the design of a naval vessel. After application of the optimum design method, its validity is shown and an optimum design of midship section is obtained. In addition, the optimum spaces or longitudinals and transverse web frames are found and the effect of main design variables can be investigated.