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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 50, Issue 6 - Dec 2013
Volume 50, Issue 5 - Oct 2013
Volume 50, Issue 4 - Aug 2013
Volume 50, Issue 3 - Jun 2013
Volume 50, Issue 2 - Apr 2013
Volume 50, Issue 1 - Feb 2013
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Experimental and Numerical Study on the Effects of Bow Deck Shape on the Green Water
Jeong, Kwang-Leol ; Lee, Young-Gill ; Ha, Yoon-Jin ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 273~281
DOI : 10.3744/SNAK.2013.50.5.273
In this paper, the effects of bow deck shape on the green water are studied by numerical and experimental method. Varying the deck shapes to triangular, elliptic and circular, the thickness and advancing velocity of green water leading edge are compared using numerical method. Also the motion, the pressure on the vertical wall and the height on the deck of green water are compared among the three bow deck shapes in the heave and pitch motion free condition by experimental method. To remove the effects of the difference of motions among the deck shapes, numerical simulations are performed varying the deck shape with the same motion. In the same motion condition, smallest impulsive pressure occurred in the condition of elliptic deck shape.
Numerical Study on the Effects of Combination of Blade Number for Shaft Forces and Moments of Contra-Rotating Propeller
Paik, Kwang-Jun ; Lee, Jinsuk ; Lee, Taegu ; Hoshino, Tetsuji ; Park, Hyung-Gil ; Seo, Jongsoo ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 282~290
DOI : 10.3744/SNAK.2013.50.5.282
The effects of the combination of blade number for forward and after propeller on the propeller shaft forces of a contra-rotating propeller (CRP) system are presented in the paper. The research is performed through the numerical simulations based on the Reynolds-Averaged Navier-Stokes equations (RANS). The simulation results of the present method in open water condition are validated comparing with the experimental data as well as the other numerical simulation results based on the potential method for 4-0-4 CRP (3686+3687A) and 4-0-5 CRP (3686+3849) of DTNSRDC. Two sets of CRP are designed and simulated to study the effect of the combination of blade number in behind-hull condition. One set consists of 3-blade and 4-blade, while the other is 4-blade and 4-blade. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. From the simulation results, the fluctuations of axial force and moment are dominant in the case of same blade numbers for forward and after propellers, whereas the fluctuations of horizontal and vertical forces and moments are very large in the case of different blade numbers.
A Study on the Estimation of the Form Factor of Full-Scale Ship by the Experimental Data of Geosim Models
Ha, Yoon-Jin ; Lee, Young-Gill ; Kang, Bong Han ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 291~297
DOI : 10.3744/SNAK.2013.50.5.291
Generally, form factor is determined through ITTC method. Determining the form factor from ITTC method includes the assumption that the form factor of a full-scale ship is the same value as its model ship. In other words, the form factor is independent on Reynolds number. However, for the more appropriate prediction of the resistance performance of a full-scale ship, the form factor must be determined with the consideration of the variation attendant on Reynolds number. In this research, several Geosim ship models are adopted to investigate the scale effect, and correlation lines of form factor are improved to suggest the better extrapolation method for the prediction of the form factor of full-scale ship. The corrected form factors using the correlation lines are compared with those determined from the results of low-speed resistance tests. To consider the influence of hull form, the correlation lines are determined for the group of high-speed ships and the group of low-speed ships, respectively. The corrected form factors have shown good agreement among the prediction results from each Geosim ship model to the full-scale ship.
Optimal Block Transportation Path Planning of Transporters considering the Damaged Path
Heo, Ye-Ji ; Cha, Ju-Hwan ; Cho, Doo-Yeoun ; Song, Ha-Cheol ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 298~306
DOI : 10.3744/SNAK.2013.50.5.298
Nowadays, a transporter manager plans the schedule of the block transportation by considering the experience of the manager, the production process of the blocks and the priority of the block transportation in shipyard. The schedule planning of the block transportation should be rearranged for the reflection of the path blocking cases occurred by unexpected obstacles or delays in transportation. In this paper, the optimal block transportation path planning system is developed for rearranging the schedule of the block transportation by considering the damaged path.
algorithm is applied to calculate the new shortest path between the departure and arrival of the blocks transported through the damaged path. In this algorithm, the first node of the damaged path is considered as the starting position of the new shortest path, and then the shortest path calculation is completed if the new shortest path is connected to the one of nodes in the original path. In addition, the data structure for the algorithm is designed. This optimal block transportation path planning system is applied to the Philippine Subic shipyard and the ability of the rapid path modification is verified.
Passenger Ship Evacuation Simulation using Algorithm for Determination of Evacuating Direction based on Walking Direction Potential Function
Ha, Sol ; Cho, Yoon-Ok ; Ku, Namkug ; Park, Kwangphil ; Lee, Kyu-Yeul ; Roh, Myung-Il ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 307~313
DOI : 10.3744/SNAK.2013.50.5.307
This paper presents a simulation for passenger ship evacuation considering determination of evacuating direction based on walking direction potential function. In order to determine walking direction of a passenger, his/her position in two dimensional plane was adopted as a design variable, and fixed boundaries such as walls and obstacles were adopted as constraints. To solve this optimum problem, a walking direction potential function was adopted as an objective function. This potential function was configured as a kind of penalty function and it contained two components. One is a potential function concerned with the distance to the destination, and other is a potential function based on the effect of walls and obstacles. To determine evacuating direction, this problem was solved by minimizing the walking direction potential function every unit time during the simulation. The crowd behavior of the passenger consisted of the flock behavior, a form of collective behavior of a large number of interacting passengers with a common group. With the proposed algorithm, the test problems in International Maritime Organization, Maritime Safety Committee/Circulation 1238(IMO MSC/Circ.1238) were implemented and the direction of passengers and total evacuation time was analyzed.
Study on Simulation Model Generation of a Shipyard Panel Block Shop using a Neutral Data Format for Production Information
Lee, Dong Kun ; Back, Myung Gi ; Lee, Kwangkook ; Park, Jun Soo ; Shin, Jong Gye ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 314~323
DOI : 10.3744/SNAK.2013.50.5.314
Production simulation technology is beneficial to solve the complicated and fluctuated problems in a shipyard. It takes too much time and effort to build simulation models in the field, though. This research proposes a feasible method to reduce the difficulties related to simulation modeling for the factory or shop capacity analysis. In addition, a proposed neutral data format for production information is efficient to manage information acquisition for simulation modeling automation. A panel block shop model is contributed to comparison between the conventional technique and the automated one. The automation technique is highly recommended to run a rapid simulation in the shipyard problem.
Experimental Verification on the Effect of the Gap Flow Blocking Devices Attached on the Semi-Spade Rudder using Flow Visualization Technique
Shin, Kwangho ; Suh, Jung-Chun ; Kim, Hyochul ; Ryu, Keuksang ; Oh, Jungkeun ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 324~333
DOI : 10.3744/SNAK.2013.50.5.324
Recently, rudder erosion due to cavitation has been frequently reported on a semi-spade rudder of a high-speed large ship. This problem raises economic and safety issues when operating ships. The semi-spade rudders have a gap between the horn/pintle and the movable wing part. Due to this gap, a discontinuous surface, cavitation phenomenon arises and results in unresolved problems such as rudder erosion. In this study, we made a rudder model for 2-D experiments using the NACA0020 and also manufactured gap flow blocking devices to insert to the gap of the model. In order to study the gap flow characteristics at various rudder deflection angles(
) and the effect of the gap flow blocking devices, we carried out the velocity measurements using PIV(Particle Image Velocimetry) techniques and cavitation observation using high speed camera in Seoul National University cavitation tunnel. To observe the gap cavitation on a semi-spade rudder, we slowly lowered the inside pressure of the cavitation tunnel until cavitation occurred near the gap and then captured it using high-speed camera with the frame rate of 4300 fps(frame per second). During this procedure, cavitation numbers and the generated location were recorded, and these experimental data were compared with CFD results calculated by commercial code, Fluent. When we use gap flow blocking device to block the gap, it showed a different flow character compared with previous observation without the device. With the device blocking the gap, the flow velocity increases on the suction side, while it decreases on the pressure side. Therefore, we can conclude that the gap flow blocking device results in a high lift-force effect. And we can also observe that the cavitation inception is delayed.
Job Assignment Simulation of Ship Hull Production Design in Consideration of Mid-Term Schedule
Son, Myeong-Jo ; Kim, Tae-Wan ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 334~342
DOI : 10.3744/SNAK.2013.50.5.334
In this paper, we analyze the procedure of the design manager for the enhancement of the hull production design process by use of the simulation method. Normally, design manager assigns design jobs according to various methods and estimates the corresponding results. When the construction drawing which is the output of the detail design where a design is dealt by zones, the design manager identifies blocks and analyzes their work difficulties, and assigns jobs to design engineers who are different in capabilities. These processes including the design engineer who can be modeled with man-hours evaluation model are represented in detail as a simulation model. As the high-level modeling for the discrete-event system, we use Event Graph model. And we implemented the simulation using Simkit which is open simulation engine for the discrete-event system. We made the simulation scenario to be written by a user in the scenario generator which is separated from the simulation model, and made the simulation result to be visualized in the form of Gantt chart in a Web. In the scenario of the irregular issuance for various construction drawings which contain different numbers of blocks, we performed the Monte-Carlo simulation according to various assignment methods to find the assignment result that satisfies the mid-term schedule.
Fluid-Structure Interaction Analysis of Two-Dimensional Wings
Ahn, Byoung-Kwon ; Lee, Suk-Jeong ; Kim, Ji-Hye ; Kim, Ki-Sup ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 343~348
DOI : 10.3744/SNAK.2013.50.5.343
When a natural frequency of the trailing edge of a wing is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appears, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, we first evaluate main features of oscillating characteristics of the wing. Second we simulate fluid-structure interaction of the wing with a flap using a commercial code, ANSYS-CFX, and investigate lift characteristics in a frequency domain.
Effect of Manufacturing Accuracy of Flexible Propeller on the Open Water Performance
Lee, Kun-Hwa ; Jang, Hyun-Gil ; Lee, Chang-Sup ; Nho, In-Sik ; Lee, Sang-Gab ; Hyun, Beom-Soo ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 349~354
DOI : 10.3744/SNAK.2013.50.5.349
The blades of flexible propellers are formed by overlaying and adhering many layers of thin glass-fiber fabric sheets, are compressed and dried in the rigid mold. The current manufacturing process can not avoid the rather irregular deformation of the blades composed of non-isotropic non-uniform fabric structures, and inevitably introduces the different shape-forming errors between blades. In this paper, several flexible model propellers are precisely measured with three-dimensional optical instrument and compared with the original design geometry. The model propellers with the as-measured geometry are evaluated with the lifting-surface-theory-based propeller analysis code. The open-water performance are presented and discussed. The importance of the manufacturing accuracy is addressed to be able to apply the flexible propellers for propulsion of marine vehicles.
Viscous Flow Analysis around a Blade Section by a Hybrid Scheme Combining a Panel Method and a CFD Method
Oh, Jin-An ; Lee, Jin-Tae ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 5, 2013, Pages 355~363
DOI : 10.3744/SNAK.2013.50.5.355
Panel methods are essential tools for analyzing a fluid-flow problem around complex three dimensional bodies, but they lack ability to solve viscous effects. On the other hand, CFD methods are considered as powerful tools for analyzing fluid-flow characteristics including viscosity. However, they also have short falls, requiring more computing time and showing different results depending on the selection of turbulence models and grid systems. In this paper a hybrid scheme combining a panel method and a CFD method is suggested. The scheme adopts a panel method for far-field solution where viscous effects are negligible and a CFD method for the solution of RANS equations in near-field where viscous effects are relatively strong. The intermediate region between the far-field and near-field is introduced where the calculated field point velocities by the panel method are given as boundary velocities for the CFD method. To verify the scheme, calculated results, by a panel method, a CFD method and the hybrid scheme, for a two dimensional foil section are compared. The suggested hybrid scheme gives reasonable results, while computation time and memory can be dramatically reduced. By using the hybrid scheme efforts can be concentrated for the local flow near the leading and trailing edges, by providing more dense grid system, where detailed flow characteristics are required.