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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 49, Issue 6 - Dec 2012
Volume 49, Issue 5 - Oct 2012
Volume 49, Issue 4 - Aug 2012
Volume 49, Issue 3 - Jun 2012
Volume 49, Issue 2 - Apr 2012
Volume 49, Issue 1 - Feb 2012
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Numerical Analysis of Ship Motions and Wave Loads Including Momentum Slamming
Hwang, Ji-Hee ; Park, In-Kyu ; Koo, Weon-Cheol ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 109~115
DOI : 10.3744/SNAK.2012.49.2.109
Slamming phenomenon may occur when a ship navigates a high sea region, where the response of ship can be expected as elastic behaviour and the resultant wave loads may increase. In this paper, numerical analysis of ship motions and wave loads including momentum slamming was performed using the strip theory with regular waves. In order to analyze the effect of slamming force on the global ship motions, time histories of each mode of displacement and forces were simulated by using Newmark-beta time integration scheme. The added mass and damping coefficients calculated by Lewis form method were compared with the results of given references. For verification of numerical results, the motion RAOs of a S175 containership were calculated as an example of application and time histories of respective displacement and vertical bending moment were compared with the results of ITTC workshop benchmark test.
Structural Design of Small Submarine Pressure Hull
Kim, Heung-Youl ; Shin, Yong-Ku ; Kim, Soo-Young ; Shin, Sung-Chul ; Chung, Bo-Young ; Jo, Jung-Hwa ; Kim, Hyun-Soo ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 116~123
DOI : 10.3744/SNAK.2012.49.2.116
This study aims to analyze the strength of pressure hull of a small submarine. The pressure hull of a submarine has to withstand very large differential pressure between hydrostatic pressure in submarine operating depth and atmospheric pressure in inner space of a submarine. To do that, the pressure hull is generally ring-stiffened cylindrical shell under external pressure. In this situation, there are some foreseeable failure modes of the pressure hull such as shell yielding, axisymmetric shell buckling, asymmetric shell buckling, overall buckling and buckling of end closure. We calculated collapse pressures of these failure modes with approximation and empirical formulas. And, to analyze critical buckling pressure, we performed eigenvalue analysis with finite element method tools.
Residual Longitudinal Strength of a VLCC Considering Probabilistic Damage Extents
Nam, Ji-Myung ; Choung, Joon-Mo ; Park, Ro-Sik ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 124~131
DOI : 10.3744/SNAK.2012.49.2.124
This paper provides prediction of ultimate longitudinal strengths of hull girder of a VLCC considering probabilistic damage extents due to collision and grounding accidents based on IMO Guideline(2003). The probability density functions of damage extents are expressed as a function of nondimensional damage variables. The accumulated probability levels of 10%, 30%, 50%, and 70% are taken into account for the damage extent estimation. The ultimate strengths have been calculated using in-house software UMADS (Ultimate Moment Analysis of Damaged Ships) which is based on the progressive collapse method. Damage indices are provided for all heeling angles due to any possible flooding of compartments from
which represent from sagging to hogging conditions, respectively. The analysis results reveal that minimum damage indices show different values according to heeling angles and damage levels.
Strength Analysis and Standardization for Closed Chocks by Using the Finite Elements Method
Jung, Jae-Wook ; Lee, Byung-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 132~145
DOI : 10.3744/SNAK.2012.49.2.132
Mooring fittings mean various devices and fittings to safely fasten vessels to quays, jetties and sea-floating buoys, etc. They include mooing winches, capstans, chocks, fairleads, guide rollers, bollards, and bitts. Not only the seats and reinforced parts for the installation of fittings but also ropes and chains for mooring and chain stoppers can be also considered. Because of damages to mooring fittings during mooring directly related to large-scale accidents such as the drifting of vessels, mooring fittings with strength appropriate for the physical features of the vessels must be installed. The reinforcement of the vessels on which the mooring fittings are installed must be designed to withstand the loads transferred from the fittings as well. Also mooring fittings with efficient strength should be required because damaged ships lead to sea pollution such as oil or fuel oil spillage. This study has been performed by the Finite Element Method for two aspects of closed chocks which are divided into structure-supporting shapes and working load. In the case of structure-supporting shapes, they have been performed in the field of sheet and bulwark. As for working load, it has been analyzed according to working load direction such as chock`s side and below. At first, strength analysis for unique closed chocks has been carried out by using the Finite Element Method, they are applied for the situation when vessels pass by the panama canal. And then the experiment has been done to verify the analyzed date obtained by FEM. The experimental results were found to be similar to the numerical results with up to 16% difference. On the basis of the results obtained, standardization has been carried out by the Finite Element Method for various sizes of closed chocks.
Free Vibration Characteristics of a Uniform String Due to Initial Conditions
Kim, Young-Joong ; Lee, Hyun-Yup ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 146~150
DOI : 10.3744/SNAK.2012.49.2.146
Free vibrations of strings due to initial conditions have been analyzed by the conventional mode summation method, and the nondimensionalized displacements and velocities have been derived in the form of infinite series. The results show wave propagating phenomena and confirmed by experiments using the high speed camera. Other physical characteristics have been discussed and examined with help of waveform solutions.
CFD Code Development Using Open Source Libraries for Shipbuilding and Marine Engineering Industries
Park, Sun-Ho ; Rhee, Shin-Hyung ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 151~157
DOI : 10.3744/SNAK.2012.49.2.151
The present study explored the possibilities of the applications of open source libraries to shipbuilding and marine engineering industries. A computational fluid dynamics (CFD) code, termed SNUFOAM, was developed and tested for turbulent flow around a ship, free surface flow around a hull, cavitating flow, and vortex shedding dynamics around a cylinder. The results using the developed CFD codes were compared against existing experimental data and solution of commercial CFD codes. SNUFOAM showed the nearly same results as commercial CFD codes and proved to be an alternative to commercial CFD codes for shipbuilding and marine engineering industries.
Analysis of Acoustic Radiation Efficiency and Underwater Radiated Noise of Double Bottom-shaped Structure
Choi, Sung-Won ; Kim, Kook-Hyun ; Cho, Dae-Seung ; Suh, Kyu-Youl ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 158~163
DOI : 10.3744/SNAK.2012.49.2.158
Recently, reducing underwater radiated noise (URN) of ships has become an environmental issue to protect marine wildlife. URN of ships can be predicted by various methods considering its generating mechanism and frequency ranges. For URN prediction due to ship structural vibration in low frequency range, the fluid-structure interaction analysis technique based on finite element and boundary element methods (FE/BEM) is regarded as an useful technique. In this paper, URN due to a double bottom-shaped structure vibration has been numerically investigated based on a coupled method of FE/BEM to enhance the prediction accuracy of URN due to the vibration of real ship engine room structure. Acoustic radiation efficiency and URN transfer function in case of vertical harmonic excitation on the top plate of double bottom structure have been evaluated. Using the results, the validity of an existing empirical formula for acoustic radiation efficiency estimation and a simple URN transfer function, which are usually adopted for URN assessment in initial design stage, is discussed.
Well Dock Design and Assessment of Relative Motions During the Operation of the Landing Crafts Within Well Dock
Yoon, Sang-Hyun ; Seo, Kwan-Hee ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 164~173
DOI : 10.3744/SNAK.2012.49.2.164
Landing ship tank with well dock has the important mission transferring troops or landing equipments from sea to shore. Such transfers are usually carried out using landing crafts, which are loaded or unloaded in flooded well dock. In this situation, as relative motions are occur between well dock and landing craft, safety verifications are demanded. In this paper, seakeeping and safety performances are investigated through model test. First of all, well dock dimensions are reviewed and model tests are performed with sea state 3&4 in 180degree wave direction. Model tests are conducted for three relative positions and seakeeping performances are investigated each position.
The Design Optimization of a Flow Control Fin Using CFD
Wie, Da-Eol ; Kim, Dong-Joon ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 174~181
DOI : 10.3744/SNAK.2012.49.2.174
In this paper, the Flow Control Fin(FCF) optimization has been carried out using computational fluid dynamics(CFD) techniques. This study focused on evaluation for the performance of the FCF attached in the stern part of the ship. The main advantage of FCF is to enhance the resistance performance through the lift generation with a forward force component on the foil section, and the propulsive performance by the uniformity of velocity distribution on the propeller plane. This study intended to evaluate these functions and to find optimized FCF form for minimizing viscous resistance and equalizing wake distribution. Four parameters of FCF are used in the study, which were angle and position of FCF, longitudinal location, transverse location, and span length in the optimization process. KRISO 300K VLCC2(KVLCC2) was chosen for an example ship to demonstrate FCF for optimization. The optimization procedure utilized genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-II(NSGA-II) for Multiobjective Optimization. The results showed that the optimized FCF could enhance the uniformity of wake distribution at the expense of viscous resistance.
A Study on The Parametric Design Method for Power Boat
Jeong, Yo-Han ; Yoo, Jae-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 182~188
DOI : 10.3744/SNAK.2012.49.2.182
The hull form design technique for high speed power boat based on the parametric design method is presented in this paper. While the design methods of conventional vessels that are currently in use have been well developed in various aspects from existing database. However, an easy and simple design program for high speed power boats needs to be provided for the relatively small boat builders who are in lack of experience and skilled manpower. This paper presents a parametric design technique which is aimed to provide an easier creation of a new model by inputting several parameters, such as angles and lengths, which correlate with hydrodynamics characteristic for high speed boats. The paper also introduces the prototype program developed to design power boat with parametric design technique.
Measurement of Sea Ice Thickness in the Arctic Ocean Using an Electromagnetic Induction Instrument
Jeong, Seong-Yeob ; Lee, Chun-Ju ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 189~195
DOI : 10.3744/SNAK.2012.49.2.189
The ice trials of the first Korean icebreaking research vessel "ARAON" were performed at the Arctic Ocean in July-August 2010. The sea ice concentrations of Arctic Ocean were 4/10 to 10/10 and the range of sea ice thickness was roughly 1.0 to 3.5m. In this research, sea ice thickness characteristics at the old ice floes were determined from results of drill hole and apparent conductivity measurements. Especially we measured apparent conductivity using an electromagnetic induction instrument (EM31-MK2) and estimated the sea ice thickness through the empirical equation from Cold Regions Research & Engineering Laboratory, CRREL. The results of estimated sea ice thickness were compared to drill hole measurement results and then, we suggest the new empirical equation to estimate sea ice thickness of single layer type sea ice during the summer season of Arctic Ocean by curve fitting approach to these data.
Numerical Analysis of Viscous Flows on Unstructured Grids Using the Optimal Method of Strongly Implicit Procedure
Shin, Young-Seop ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 196~202
DOI : 10.3744/SNAK.2012.49.2.196
In this study, numerical analysis of viscous flows is carried out based on the unstructured grid. There exist some difficulties in expressing and computing numerical derivatives on the unstructured grid due to lack of the structured characteristics. The general computer algorithms are developed to perform numerical derivatives easily and extended to be applicable to various geometries composed of hybrid meshes. And the optimal method of strongly implicit procedure is newly contrived to accelerate the rate of convergence in solving the pressure Poisson equation. To verify numerical schemes, the driven cavity problems of 2 and 3 dimension are simulated. The numerical results are compared with others and our numerical schemes are shown to be valid.
Experimental Approach for Estimation of Hydrodynamic Force Acting on a Submerged Streamlined Body Translating in a One-end-opened Cylindrical Tube
Yeo, Dong-Jin ; Kim, Yeon-Gyu ; Kim, Dong-Hun ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 2, 2012, Pages 203~211
DOI : 10.3744/SNAK.2012.49.2.203
The main object of this experiment is to estimate the hydrodynamic forces acting on a submerged streamlined body placed in a one-end-opened cylindrical tube moving with certain translational velocity. The best experimental design for this object is mimicking real situation, however sizes of model body and cylinder tube are just the same as those of real, for avoiding scale effects, mimicking real situation is not realizable. Hence, in this experiment, target body and cylindrical tube were designed to be towed with varying body position relative to cylindrical tube. For measuring hydrodynamic forces and flow velocity in the cylindrical tube, six one-component load cells and several one-hole Pitot tubes were used. Several conditions were checked with various end-plates those had different opening areas. Experiment results show that forces and flow velocity had different tendency with those expected, and the presence of a end-plate slows down the flow velocity in the cylindrical tube and affects pressure field in the tube to push the model submerged body forward of the tube. This tendency grows with decreasing opened area.