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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 52, Issue 6 - Dec 2015
Volume 52, Issue 5 - Oct 2015
Volume 52, Issue 4 - Aug 2015
Volume 52, Issue 3 - Jun 2015
Volume 52, Issue 2 - Apr 2015
Volume 52, Issue 1 - Feb 2015
Selecting the target year
A Study on Weight Estimation Model of Floating Offshore Structures using Enhanced Genetic Programming Method
Um, Tae-Sub ; Roh, Myung-Il ; Shin, Hyunkyoung ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 1~7
DOI : 10.3744/SNAK.2015.52.1.1
The weight estimation of floating offshore structures such as FPSO, TLP, semi-Submersibles, Floating Offshore Wind Turbines etc. in the preliminary design, is one of direct measures of both construction cost and basic performance. Through both literature investigation and internet search, the weight data of floating offshore structures such as FPSO and TLP was collected. In this study, the weight estimation model with the genetic programming was suggested for FPSO. The weight estimation model using genetic programming was established by fixing the independent variables based on this data. In addition, the correlation analysis was performed to make up for the weak points of genetic programming; it is apt to induce over-fitting when the number of data is relatively smaller than that of independent variables. That is, by reducing the number of variables through the analysis of the correlation between the independent variables, the increasing effect in the number of weight data can be expected. The reliability of the developed weight estimation model was within 2% of error rate.
Design and Performance Evaluation of Superstructure Modification for Air Drag Reduction of a Container Ship
Kim, Yoonsik ; Kim, Kwang-Soo ; Jeong, Seong-Wook ; Jeong, Seung-Gyu ; Van, Suak-Ho ; Kim, Jin ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 8~18
DOI : 10.3744/SNAK.2015.52.1.8
Reduction of the fuel oil consumption and corresponding greenhouse gas exhausted from ships is an important issue for today's ship design and shipping. Several concepts and devices on the superstructure of a container ship were suggested and tested in the wind tunnel to estimate the air drag reduction. As a preliminary performance evaluation, air drag contributions of each part of the superstructure and containers were estimated based on RANS simulation respectively. Air drag reduction efficiency of shape modification and add-on devices on the superstructure and containers was also estimated. Gap-protectors between containers and a visor in front of upper deck were found to be most effective for drag reduction. Wind tunnel tests had been carried out to confirm the drag reduction performance between the baseline(without any modification) configuration and two modified superstructure configurations which were designed and chosen based on the computation results. The test results with the modified configurations show considerable aerodynamic drag reduction, especially the gap-protectors between containers show the largest reduction for the wide range of heading angles. RANS computations for three configurations were performed and compared with the wind tunnel tests. Computation result shows the similar drag reduction trend with experiment for small heading angles. However, the computation result becomes less accurate as heading angle is increasing where the massively separated flow is spread over the leeward side.
A Study on Freezing Efficiency Improvement of Horizontal-Plate Freezer for Fishing Vessel
Lee, Jae-Chul ; Jeong, Ji-Ho ; Kim, Byung-Mok ; Shin, Sung-Chul ; Kim, Soo-Young ; Jeong, Bo-Yong ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 19~24
DOI : 10.3744/SNAK.2015.52.1.19
The economic efficiency for fishery products can be related to their freshness and the quality. In order to freshly storage the product, freezing equipment system is necessary for fishing vessels. For this purpose, the horizontal plate freezer (HPF) is mostly used. In this research, our major objective is to improve the freezing performance of the HPF. Therefore, it is important to analyse the relationship between the shape of channels and the cooling temperature of the HPF. In order to save calculation time while checking the trend analysis between shape and performance, we used scaled models, and evaluate the cooling temperature of full scale model based on trend analysis results. The produced HPF in domestic was used, and the same operating conditions are considered. Based on this paper, the future research will be a comparison and verification through the experiments.
Natural Frequency of 2-Dimensional Cylinders in Heaving; Frequency-Domain Analysis
Song, Je-Ha ; Lee, Seung-Joon ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 25~33
DOI : 10.3744/SNAK.2015.52.1.25
Following the previous works on the natural frequency of heaving circular cylinder, i.e. Lee and Lee (2013) and Kim and Lee (2013), an investigation of the same spirit on the 2-dimensional cylinder of Lewis form has been conducted. As before, the natural frequency is defined as that corresponding to the local maximum of the MCFR (Modulus of Complex Frequency Response), which is given by the equation of motion in the frequency domain analysis. Hydrodynamic coefficients were found by using the Ursell-Tasai method, and numerical results for them were obtained up to much higher frequencies than before, for which the method was known as numerically unstable in the past. For a wide range of H, the beam-draft ratio, and
, the sectional area coefficient, including their practical ranges for a ship, results for the natural frequency were computed and presented in this work. Two approximate values for the natural frequency, one proposed by Lee (2008) and another one by the damped harmonic oscillator, were also compared with the current results, and for most cases it was observed that the current result is between the two values. Our numerical results showed that the values of the local maximum of MCFR as well as the natural frequencye increase as
increases while H decreases. At present, extension of the present finding to the 3-dimensional ship via the approximate theory like the strip method looks promising.
Performance Test of 5.5MW Azimuth Thruster Model in LCT(Large Cavitation Tunnel)
Paik, Bu-Geun ; Park, Young-Ha ; Kim, Ki-Sup ; Kim, Ju-In ; Na, Yun-Cheol ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 34~42
DOI : 10.3744/SNAK.2015.52.1.34
The development of an azimuth thruster which has the function of dynamic positioning and propulsion has been greatly required as the demand of vehicles with it increases. To develop or design a reliable azimuth thruster, it is appropriate that the performance and cavitation observation tests should be conducted in the regime of high Reynolds number. In the present study, to satisfy high Reynolds number condition new dynamometer for a large azimuth thruster is manufactured and arranged in the test section of the Large Cavitation Tunnel (LCT). The test method composed of the open water and the cavitation observation tests is established successfully in LCT, considering the thruster design.
A Study on Effect of Aerodynamic Loads on Mooring Line Responses of a Floating Offshore Wind Turbine
Kim, Hyungjun ; Han, Seungoh ; Choung, Joonmo ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 43~51
DOI : 10.3744/SNAK.2015.52.1.43
This paper presents effect of aerodynamic loads on mooring line responses of a floating offshore wind turbine. A Matlab code based on blade element momentum (BEM) theory is developed to consider aerodynamic loads acting on NREL 5MW wind turbine. The aerodynamic loads are coupled with time-domain hydrodynamic analyses using one-way interaction scheme of the wave and wind loads. A semi-submersible floating platform which is from Offshore Code Comparison Collaborative Continuation(OC4) DeepCWind platform is used with catenary mooring lines simply composed of studless chain links. Average values of mooring peak tensions obtained from aerodynamic load consideration are significantly increased compared to those from simple wind drag force consideration. Consideration of aerodynamic loads also yield larger tension ranges which can be important factor to reduce fatigue life of the mooring lines.
Development of Progressive Failure Analysis Method for Composite Laminates based on Puck's Failure Criterion-Damage Mechanics Coupling Theories
Lee, Chi-Seung ; Lee, Jae-Myung ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 52~60
DOI : 10.3744/SNAK.2015.52.1.52
In the present study, an evaluation method for progressive failure of composite laminates has been proposed based on Puck's failure criterion and damage mechanics. The initial failure (or initiation of crack/delamination) has been assessed using Puck's failure criterion, and the progressive failure (or growth of crack/delamination) has been evaluated using fiber- and matrix-dependent damage variables. Based on Puck's failure criterion-damage mechanics coupling theories, the ABAQUS user-defined subroutine UMAT has been developed in order to analyze the progressive failure of glass/carbon fiber-reinforced composite laminates efficiently. In addition, the developed subroutine has been applied to progressive failure problem of industrial composite laminates, and the analysis results has been compared to experimental results which have been already reported in publications. It was confirmed that the simulation results were coincided well with the reported composite failure results.
Effects of Propeller Forces on the Propeller Shaft Bearing during Going Straight and Turning of Ship
Shin, Sang-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 61~69
DOI : 10.3744/SNAK.2015.52.1.61
In the beginning of the 1990's, numerous shaft bearing damages, especially in aft stern tube bearing, were reported. The main reasons of bearing damages were estimated that hull deflections have been increased by more flexible hulls and propeller dynamic loads have not been considered in shaft alignment. After that time, studies to take into account hull deflections in shaft alignment have been actively carried out, but for the latter leave much to be desired. In this study, the effects of the propeller forces on the propeller shaft bearing have been investigated by estimating thrust eccentricity as reasonable as possible although some assumptions to simulate turning of ship were introduced. Three dimensional nominal wake to estimate thrust eccentricity have been calculated by using CFD analysis and model test in the towing tank. This study presents the procedure to estimate the propeller eccentric forces and their influence on the stern tube bearing for a container carrier. As a result, it has been found that the lateral propeller forces in turning condition should be considered in shaft alignment to prevent shaft bearing damages.
Curvature Region Analysis for Application of Plates Forming
Kim, Chan Suk ; Son, Seung Hyeok ; Shin, Jong Gye ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 70~76
DOI : 10.3744/SNAK.2015.52.1.70
The ship hull is accomplished by assembling various curved surfaces. There are numerous existing methods for ship hull processing, which need certain appropriate processing methods to enable it to be more efficient. The curved hull plates can be divided into convex region and saddle region. It is common to use line heating method to form a saddle region, when it comes to a convex region, it will be triangle heating method to be utilized. A precise analysis for curvature domain is required for the application of proper processing method. There exist various problems on existing calculation methods of curvature domain. Therefore, a more powerful method is demanded to it more accurately. In this study, a method called Dual Contouring is applied to extract curved surfaces, which is able to improve accuracy of extracted area. Based on all above, a best-suited heat processing method should be selected.
Multi-floor Layout Model for Topsides of Floating Offshore Plant using the Optimization Technique
Jeong, Se-Yong ; Roh, Myung-Il ; Shin, Hyunkyoung ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 77~87
DOI : 10.3744/SNAK.2015.52.1.77
For a floating offshore plant such as FPSO(Floating, Production, Storage, and Off-loading unit), various equipment should be installed in the restricted space, as compared with an onshore plant. The requirement for an optimal layout method of the plant has been increased in these days. Thus, a layout method of the floating offshore plant was proposed in this study. For this, an optimization problem for layout design was mathematically formulated, and then an optimization algorithm based on the genetic algorithm was implemented with C++ language in order to solve it. Finally, the proposed method was applied to an example of FPSO topsides. As a result, it was shown that the proposed method can be applied to layout design of the floating offshore plant such as FPSO.
Development of a Fatigue Damage Model of Wideband Process using an Artificial Neural Network
Kim, Hosoung ; Ahn, In-Gyu ; Kim, Yooil ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 1, 2015, Pages 88~95
DOI : 10.3744/SNAK.2015.52.1.88
For the frequency-domain spectral fatigue analysis, the probability density function of stress range needs to be estimated based on the stress spectrum only, which is a frequency domain representation of the response. The probability distribution of the stress range of the narrow-band spectrum is known to follow the Rayleigh distribution, however the PDF of wide-band spectrum is difficult to define with clarity due to the complicated fluctuation pattern of spectrum. In this paper, efforts have been made to figure out the links between the probability density function of stress range to the structural response of wide-band Gaussian random process. An artificial neural network scheme, known as one of the most powerful system identification methods, was used to identify the multivariate functional relationship between the idealized wide-band spectrums and resulting probability density functions. To achieve this, the spectrums were idealized as a superposition of two triangles with arbitrary location, height and width, targeting to comprise wide-band spectrum, and the probability density functions were represented by the linear combination of equally spaced Gaussian basis functions. To train the network under supervision, varieties of different wide-band spectrums were assumed and the converged probability density function of the stress range was derived using the rainflow counting method and all these data sets were fed into the three layer perceptron model. This nonlinear least square problem was solved using Levenberg-Marquardt algorithm with regularization term included. It was proven that the network trained using the given data set could reproduce the probability density function of arbitrary wide-band spectrum of two triangles with great success.