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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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Laminar Flow Structures Near a Circular Cylinder in between a Free-Surface and a Moving Wall
Seo, Jang-Hoon ; Jung, Jae-Hwan ; Yoon, Hyun-Sik ; Park, Dong-Woo ; Chun, Ho-Hwan ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 213~221
DOI : 10.3744/SNAK.2012.49.3.213
The present study numerically investigates the interaction between a free-surface and flow around a circular cylinder over a moving wall. In order to simulate the flow past the circular cylinder over a moving wall near a free-surface, this study has adopted the direct-forcing/fictitious domain (DF/FD) method with the level set method in the Cartesian coordinates. Numerical simulation is performed for a Reynolds numbers of 100 in the range of
, where g/D and h/D are the gaps between the cylinder and a moving wall and the cylinder and a free-surface normalized by cylinder diameter D, respectively. According to g/D and h/D, the vortex structures have been classified into three patterns of the two-row, one-row, steady elongation. In general, both of g/D and h/D have the large values which mean the cylinder is far away from the wall and the free-surface, two-row vortex structure forms in the wake. When g/D decreases, the two-row vortex structure gradually transfers into the one-row vortex structure. When the g/D reveals the critical value below which the flow becomes steady state, resulting in the steady elongation vortex.
A Prediction of Out-of-Plane Deformation on a Deck Plate by Temperature Difference between Steel and Air
Ha, Yun-Sok ; Yi, Myung-Su ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 222~226
DOI : 10.3744/SNAK.2012.49.3.222
When ship blocks are erected or pre-erected, most blocks will be at outdoors where they are not protected from weather and exposed to ray of the sun. A deck plate compared to those in radiation heat transfer from the sun will have higher temperature than it of ambient air, and will expand more than lower laying structures whose temperatures are similar with air. But deck plates and under-structures are connected, so the deck plate will be under out-of-plane deformation rather than expand in length. In this study, we considered the temperature difference between air and plate as a major parameter of out-of-plane deformation, and analyzed how much additional deformation would take place. In addition, when a deformation could take place was also analyzed based on the initial deformed shape of deck plate. Because the accuracy inspections of deck plate will be done during daytime, conventional accuracy check results on sunny day could make us feel unfair. Thus resonable datum about momentary additional out-of-plane deformation due to environmental effects have been determined. The real deformation values can be specified even under enlarged deformations by radiation-expansion.
Low Temperature Plastic Hardening Constitutive Equation for Steels of Polar Class Vessels
Min, Dug-Ki ; Heo, Young-Mi ; Cho, Sang-Rai ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 227~231
DOI : 10.3744/SNAK.2012.49.3.227
In this study, a plastic hardening constitutive equation for steels of polar class vessels at low temperature is proposed. The equation was derived using the experimental data obtained from tensile tests at room and low temperatures. Tensile tests at low temperature are both costly and time consuming because an expensive cold chamber is necessary and it takes too much time to cool down a specimen to set temperature. Using the proposed plastic hardening constitutive equation the plastic hardening characteristics of steels for polar class vessels at low temperature can be easily predicted from the tensile test results at room temperature.
On the Plastic Deformation of Polar-Class Ship's Single Frame Structures Subjected to Collision Loadings
Min, Dug-Ki ; Shin, Dong-Wan ; Kim, Sin-Ho ; Heo, Yeoung-Mi ; Cho, Sang-Rai ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 232~238
DOI : 10.3744/SNAK.2012.49.3.232
The effects of temperature on the structural behavior of polar class vessels have been experimentally and numerically investigated. Experiments were carried out on single frame structures made of steel material, DH36, which is used for outer shell of the vessels making transit through the polar region. A knife edge type striker was dropped down onto single frame structures. The temperatures of the single frames were set to
and room temperature. The deflection around the mid-point of the single frame was measured and numerically simulated using finite element model. Strain rate effect on the structural behavior has been investigated and turned out that the strain rate effect can be neglected. From the results of the experiment and numerical analyses, it has been noticed that the permanent deflection at lower temperature was reduced due to a temperature hardening of material as expected.
Fire Safety Assessment Based on FSA and Risk Reduction of Machinery System Considering Functional Safety
Suh, Sung-Won ; Yang, Young-Soon ; Chung, So-Yeon ; Ryu, Won-Sun ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 239~246
DOI : 10.3744/SNAK.2012.49.3.239
It is the well-known fact that most part of goods transported are moved on the unfavorable ocean and even a small amount of accident on sea is extremely dangerous for human lives, financial losses, and social responsibility. Among the several causes of accidents, those by fire have occurred frequently and their damage has been highly serious. The aim of this paper is to assess the risk of fires due to oil leakage in the machinery space. To define the possible fire scenario, our team has performed the search of casualty database and reviewed the previous and various studies in the field. As a result, it is noted that the quantitative risk of the fire scenario have been evaluated on the ground of the FSA risk model. The expected frequency of a fire amounts to incidents during the life of a ship, and the expected financial damage amounts to 5,654 USD per a ship. By adopting Safety Instrumented System (SIS) introduced in IEC 61508 and IEC 61511, SIS model is designed to prevent oil leakage fire as a risk reduction method. It is concluded that System Integrity Level (SIL) 1 seems to be appropriate level of SIS.
Study on the Effects of Surface Roughness and Turbulence Intensity on Dam-break Flows
Park, Il-Ryong ; Jung, Kwang-Hyo ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 247~253
DOI : 10.3744/SNAK.2012.49.3.247
Dam-break flows, a type of very shallow gravity-driven flow, are substantially influenced by resistance forces due to viscous friction and turbulence. Assuming turbulent flow, the main focus of this study is to validate the increase of drag forces caused by surface roughness and especially turbulence intensity. A Reynolds Averaged Navier-Stokes(RANS) approach with the standard k-
turbulence model is used for this study, where the free surface motion is captured by using a volume of fluid(VOF) method. Surface roughness effects are considered through the law of the wall modified for roughness, while the initial turbulence intensity which determines the lowest level of turbulence in the flow domain of interest is used for the variation of turbulence intensity. It has been found that the numerical results at higher turbulence intensities show a reasonably good agreement with the physical aspects shown by two different dam-break experiments without and with the impact of water.
Vulnerability Assessment Procedure for the Warship Including the Effect of Shotline and Penetration of Fragments
Kim, Kwang-Sik ; Lee, Jang-Hyun ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 254~263
DOI : 10.3744/SNAK.2012.49.3.254
The survivability of warship is assessed by susceptibility, vulnerability and recoverability. Essentially, a vulnerability assessment is a measure of the effectiveness of a warship to resist hostile weapon effects. Considering the shot line and its penetration effect on the warship, present study introduces the procedural aspects of vulnerability assessments of warship. Present study also considers the prediction of penetration damage to a target caused by the impact of projectiles. It reflects the interaction between the weapon and the target from a perspective of vulnerable area method and COVART model. The shotline and tracing calculation have been directly integrated into the vulnerability assessment method based on the penetration equation empirically obtained. A simplified geometric description of the desired target and specification of a threat type is incorporated with the penetration effect. This study describes how to expand the vulnerable area assessment method to the penetration effect. Finally, an example shows that the proposed method can provide the vulnerability parameters of the warship or its component under threat being hit through tracing the shotline path thereby enabling the vulnerability calculation. In addition, the proposed procedure enabling the calculation of the component's multi-hit vulnerability introduces a propulsion system in dealing with redundant Non-overlapping components.
A Study on the Infrared Signature of a Naval Ship under the Marine Climate
Kim, Yoon-Sik ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 264~272
DOI : 10.3744/SNAK.2012.49.3.264
A study on the IR(InfraRed) signature of a naval ship has been performed using well known IR signature analysis software, ShipIR/NTCS. Variations of the IR signature radiated from skins of a naval ship have been investigated according to the monthly averaged marine climate conditions. An unclassified destroyer model with and without applying the washdown system was applied to compare the influence on the signature under the background changes. The marine background models were created from the observed data by a buoy of Korea Meterological Administration(KMA). The sensitivity of the ship signature against the climate variables such as air temperature, sea temperature, relative humidity has been studied as well. The seasons which show extreme(max, min) skin signature change by whether the washdown is applied or not. The sensitivities of the air temperature and the sea temperature for a dry-ship reversed by applying the washdown on the ship surfaces.
Dynamic Analysis of Floating Multi-Bodies Considering Crane Impact Loads
Kim, Young-Bok ; Kim, Yong-Yook ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 3, 2012, Pages 273~279
DOI : 10.3744/SNAK.2012.49.3.273
The concept of the Mobile Harbor had been made recently as a kind of feeder vehicle to transfer a certain amount of container boxes (i.e. 250 TEU at a time) from main ocean container vessels over 5,000 TEU capacity to the container terminal on land. In a harbor a short distance apart from the land, the container loading/unloading operation has to be performed on the main deck of the Mobile Harbor using the container cranes in the state of side-by-side mooring with protection of fenders and robot arms in the gap. Even under the ocean condition of the sea state class 2 or 3, the operation has to be confirmed to be safely performed. In this situation, the floating bodies considering the multiple-body interaction effect also has to be examined whether they might behave safely or not. Especially, this study focuses on the dynamic behavior of the Mobile harbor when a container box is hanged on the crane and the impact load due to the slewing motion is imposed in a certain sea state. The motion response should be controlled within the motion level to assure the safe operation.