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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
International Journal of Naval Architecture and Ocean Engineering
Journal Basic Information
Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 5, Issue 4 - Dec 2013
Volume 5, Issue 3 - Sep 2013
Volume 5, Issue 2 - Jun 2013
Volume 5, Issue 1 - Mar 2013
Selecting the target year
Numerical analysis for supercavitating flows around axisymmetric cavitators
Kwack, Young Kyun ; Ko, Sung Ho ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 325~332
DOI : 10.3744/JNAOE.2013.5.3.325
Diffuse interface model for numerical analysis was used to compute supercavitating flows around various cavitators. The ambient pressures of 2 atm permitted cavitation studies in a range of cavitation number,
to 1.0 on selected conical and disk-headed cavitors. The computed results were compared with relation by Reichardt. Drag coefficient obtained from pressure forces acting on the cavitator also compared well with those obtained from analytical relations.
Numerical simulation of wave interacting with a free rolling body
Jung, Jae Hwan ; Yoon, Hyun Sik ; Chun, Ho Hwan ; Lee, Inwon ; Park, Hyun ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 333~347
DOI : 10.3744/JNAOE.2013.5.3.333
The present study numerically models the interaction between a regular wave and the roll motion of a rectangular floating structure. In order to simulate two-dimensional incompressible viscous two-phase flow in a numerical wave tank with the rectangular floating structure, the present study used the volume of fluid method based on the finite volume method. The sliding mesh technique is adopted to handle the motion of the rectangular floating structure induced by fluid-structure interaction. The effect of the wave period on the flow, roll motion and forces acting on the structure is examined by considering three different wave periods. The time variations of the wave height and the roll motion of the rectangular structure are in good agreement with experimental results for all wave periods. The present response amplitude operator is in good agreement with experimental results with the linear potential theory. The present numerical results effectively represent the entire process of vortex generation and evolution described by the experimental results. The longer wave period showed a different mechanism of the vortex evolution near each bottom corner of the structure compared to cases of shorter wave periods. In addition, the x-directional and z-directional forces acting on the structure are analyzed.
A study on an efficient prediction of welding deformation for T-joint laser welding of sandwich panel PART I : Proposal of a heat source model
Kim, Jae Woong ; Jang, Beom Seon ; Kim, Yong Tai ; Chun, Kwang San ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 348~363
DOI : 10.3744/JNAOE.2013.5.3.348
The use of I-Core sandwich panel has increased in cruise ship deck structure since it can provide similar bending strength with conventional stiffened plate while keeping lighter weight and lower web height. However, due to its thin plate thickness, i.e. about 4~6 mm at most, it is assembled by high power
laser welding to minimize the welding deformation. This research proposes a volumetric heat source model for T-joint of the I-Core sandwich panel and a method to use shell element model for a thermal elasto-plastic analysis to predict welding deformation. This paper, Part I, focuses on the heat source model. A circular cone type heat source model is newly suggested in heat transfer analysis to realize similar melting zone with that observed in experiment. An additional suggestion is made to consider negative defocus, which is commonly applied in T-joint laser welding since it can provide deeper penetration than zero defocus. The proposed heat source is also verified through 3D thermal elasto-plastic analysis to compare welding deformation with experimental results. A parametric study for different welding speeds, defocus values, and welding powers is performed to investigate the effect on the melting zone and welding deformation. In Part II, focuses on the proposed method to employ shell element model to predict welding deformation in thermal elasto-plastic analysis instead of solid element model.
Undergraduate courses for enhancing design ability in naval architecture
Lee, Kyu-Yeul ; Ku, Namkug ; Cha, Ju-Hwan ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 364~375
DOI : 10.3744/JNAOE.2013.5.3.364
Contemporary lectures in undergraduate engineering courses typically focus on teaching major technical knowledge-based theories in a limited time. Therefore, most lectures do not allow the students to gain understanding of how the theories are applied, especially in Naval Architecture and Ocean Engineering departments. Shipyards require students to acquire practical ship design skills in undergraduate courses. To meet this requirement, two lectures are organized by the authors; namely, "Planning Procedure of Naval Architecture & Ocean Engineering" (PNAOE) and "Innovative Ship Design" (ISD). The concept of project-based and collaborative learning is applied in these two lectures. In the PNAOE lecture, sophomores receive instruction in the designing and building of model ships, and the students' work is evaluated in a model ship contest. This curriculum enables students to understand the concepts of ship design and production. In the ISD lecture, seniors learn how to develop their creative ideas about ship design and communicate with members of group. They are encouraged to cooperate with others and understand the ship design process. In the capstone design course, students receive guidance to facilitate understanding of how the knowledge from their sophomore or junior classes, such as fluid mechanics, statics, and dynamics, can be applied to practical ship design. Students are also encouraged to compete in the ship design contest organized by the Society of Naval Architects of Korea. Moreover, the effectiveness of project-based and collaborative learning for enhancing interest in the shipbuilding Industry and understanding the ship design process is demonstrated by citing the PNAOE and ISD lectures as examples.
Concurrent engineering solution for the design of ship and offshore bracket parts and fabrication process
Kim, Tae-Won ; Lim, Sang-Sub ; Seok, Ho-Hyun ; Kang, Chung-Gil ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 376~391
DOI : 10.3744/JNAOE.2013.5.3.376
Brackets in ships and offshore structures are added structures that can endure stress concentrations. In this study, a concurrent engineering solution was proposed, and a high strength low carbon cast steel alloy applicable to offshore structures was designed and developed. The yield strength and ultimate tensile strength of the designed steel were 480 and 600 MPa, respectively. The carbon equivalent of the steel was 0.446 with a weld crack susceptibility index of 0.219. The optimal structural design of the brackets for offshore structures was evaluated using ANSYS commercial software. The possibility of replacing an assembly of conventional built-up brackets with a single casting bulb bracket was verified. The casting process was simulated using MAGMAsoft commercial software, and a casting fabrication process was designed. For the proposed bulb bracket, it was possible to reduce the size and weight by approximately 30% and 50%, respectively, compared to the conventional type of bracket.
Development of indirect EFBEM for radiating noise analysis including underwater problems
Kwon, Hyun-Wung ; Hong, Suk-Yoon ; Song, Jee-Hun ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 392~403
DOI : 10.3744/JNAOE.2013.5.3.392
For the analysis of radiating noise problems in medium-to-high frequency ranges, the Energy Flow Boundary Element Method (EFBEM) was developed. EFBEM is the analysis technique that applies the Boundary Element Method (BEM) to Energy Flow Analysis (EFA). The fundamental solutions representing spherical wave property for radiating noise problems in open field and considering the free surface effect in underwater are developed. Also the directivity factor is developed to express wave's directivity patterns in medium-to-high frequency ranges. Indirect EFBEM by using fundamental solutions and fictitious source was applied to open field and underwater noise problems successfully. Through numerical applications, the acoustic energy density distributions due to vibration of a simple plate model and a sphere model were compared with those of commercial code, and the comparison showed good agreement in the level and pattern of the energy density distributions.
Towed underwater PIV measurement for free-surface effects on turbulent wake of a surface-piercing body
Seol, Dong Myung ; Seo, Jeong Hwa ; Rhee, Shin Hyung ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 404~413
DOI : 10.3744/JNAOE.2013.5.3.404
In the present study, a towed underwater particle image velocimetry (PIV) system was validated in uniform flow and used to investigate the free-surface effects on the turbulent wake of a simple surface-piercing body. The selected test model was a cylindrical geometry formed by extruding the Wigley hull's waterplane shape in the vertical direction. Due to the constraints of the two-dimensional (2D) PIV system used for the present study, the velocity field measurements were done separately for the vertical and horizontal planes. Using the measured data at several different locations, it was possible to identify the free-surface effects on the turbulent wake in terms of the mean velocity components and turbulence quantities. In order to provide an accuracy level of the data, uncertainty assessment was done following the International Towing Tank Conference standard procedure.
Numerical and experimental investigation of conventional and un-conventional preswirl duct for VLCC
Shin, Hyun-Joon ; Lee, Jong-Seung ; Lee, Kang-Hoon ; Han, Myung-Ryun ; Hur, Eui-Beom ; Shin, Sung-Chul ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 414~430
DOI : 10.3744/JNAOE.2013.5.3.414
This paper shows the study of preswirl duct as an effective energy saving devices that have been devised and reviewed to support the propeller performance, especially for the ship of VLCC with large block coefficients. From the bare hull wake measurements, typical upper/lower asymmetry of hull wake at the propeller disk was found. The 2 kinds of pre-swirl duct, Unconventional half circular duct and Conventional circular pre-swirl duct have been designed and reviewed to recover the loss of propeller running in that condition. The general function of the pre-swirl duct was set to work against this asymmetry of wake and generate pre-swirled flow into the propeller against the propeller rotating direction. The optimum self propulsion tests with various angle configurations were carried out and the best configuration was decided. Accordingly, cavitation test was carried out with best configuration of unconventional half circular duct. The blade surface and tip vortex cavitation behaved smoother when the duct was mounted. The hull pressure amplitudes reflected this difference, so the hull pressure amplitude with duct was smaller than that of without duct.
Practical investigation of a monopod fabrication method and the numerical investigation of its up-righting process
Hafez, Khaled A. ; Ismael, Maged M. ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 431~453
DOI : 10.3744/JNAOE.2013.5.3.431
The principal purpose of this paper is to present a novel two phases rational scenario applied in constructing an offshore monopod platform; in which the two phases are the all-ground horizontal construction phase and the post-construction phase. Concerning the all-ground construction phase, a brief investigation of its different stages, i.e., pre-fabrication, fabrication, pre-assembling, positioning, assembling, and surface finishing is introduced. The important practical aspects of such construction phase are investigated without going into the nitty-gritty of the details involved therein. Concerning the post-construction phase, a clear investigation of its sequential stages, i.e., lifting, moving and up-righting is introduced. A finite element model (FEM) of the monopod platform is created to perform the structural analysis necessary to decide the suspension points/devices and the handling scenario during the various stages of the post-construction phase on a rational wise. Such structural analysis is performed within the framework of the three dimensional quasi-static modeling and analysis aiming at simulating the realistic handling condition, and hence introducing a reliable physical interpretation of the numerical results. For the whole effort to be demonstrated efficiently, the results obtained are analyzed, the conclusions are presented, and few related recommendations are suggested.
Optimization of ship inner shell to improve the safety of seagoing transport ship
Yu, Yan-Yun ; Lin, Yan ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 454~467
DOI : 10.3744/JNAOE.2013.5.3.454
A practical Ship Inner Shell Optimization Method (SISOM), the purpose of which is to improve the safety of the seagoing transport ship by decreasing the maximum Still Water Bending Moment (SWBM) of the hull girder under all typical loading conditions, is presented in this paper. The objective of SISOM is to make the maximum SWBM minimum, and the section areas of the inner shell are taken as optimization variables. The main requirements of the ship performances, such as cargo hold capacity, propeller and rudder immersion, bridge visibility, damage stability and prevention of pollution etc., are taken as constraints. The penalty function method is used in SISOM to change the above nonlinear constraint problem into an unconstrained one, which is then solved by applying the steepest descent method. After optimization, the optimal section area distribution of the inner shell is obtained, and the shape of inner shell is adjusted according to the optimal section area. SISOM is applied to a product oil tanker and a bulk carrier, and the maximum SWBM of the two ships is significantly decreased by changing the shape of inner shell plate slightly. The two examples prove that SISOM is highly efficient and valuable to engineering practice.
The development of a practical pipe auto-routing system in a shipbuilding CAD environment using network optimization
Kim, Shin-Hyung ; Ruy, Won-Sun ; Jang, Beom Seon ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 468~477
DOI : 10.3744/JNAOE.2013.5.3.468
An automatic pipe routing system is proposed and implemented. Generally, the pipe routing design as a part of the shipbuilding process requires a considerable number of man hours due to the complexity which comes from physical and operational constraints and the crucial influence on outfitting construction productivity. Therefore, the automation of pipe routing design operations and processes has always been one of the most important goals for improvements in shipbuilding design. The proposed system is applied to a pipe routing design in the engine room space of a commercial ship. The effectiveness of this system is verified as a reasonable form of support for pipe routing design jobs. The automatic routing result of this system can serve as a good basis model in the initial stages of pipe routing design, allowing the designer to reduce their design lead time significantly. As a result, the design productivity overall can be improved with this automatic pipe routing system.
Approximate natural vibration analysis of rectangular plates with openings using assumed mode method
Cho, Dae Seung ; Vladimir, Nikola ; Choi, Tae Muk ;
International Journal of Naval Architecture and Ocean Engineering, volume 5, issue 3, 2013, Pages 478~491
DOI : 10.3744/JNAOE.2013.5.3.478
Natural vibration analysis of plates with openings of different shape represents an important issue in naval architecture and ocean engineering applications. In this paper, a procedure for vibration analysis of plates with openings and arbitrary edge constraints is presented. It is based on the assumed mode method, where natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. The presented solution represents an extension of a procedure for natural vibration analysis of rectangular plates without openings, which has been recently presented in the literature. The effect of an opening is taken into account in an intuitive way, i.e. by subtracting its energy from the total plate energy without opening. Illustrative numerical examples include dynamic analysis of rectangular plates with rectangular, elliptic, circular as well as oval openings with various plate thicknesses and different combinations of boundary conditions. The results are compared with those obtained by the finite element method (FEM) as well as those available in the relevant literature, and very good agreement is achieved.