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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 48, Issue 6 - Dec 2011
Volume 48, Issue 5 - Oct 2011
Volume 48, Issue 4 - Aug 2011
Volume 48, Issue 3 - Jun 2011
Volume 48, Issue 2 - Apr 2011
Volume 48, Issue 1 - Feb 2011
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Experimental Study on Lift Characteristics Considering Moving Ground Effects of Low Aspect Ratio Wings for Wing-In Ground Effect Crafts
Ahn, Byoung-Kwon ; Koo, Sung-Phil ; Lew, Jae-Moon ; Nho, In-Sik ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 381~389
DOI : 10.3744/SNAK.2011.48.5.381
In this study, we are focusing our attention on lift characteristics of the low aspect wings for Wing-In Ground effect crafts (WIG). Experimental measurements at an open-type wind tunnel are carried out and results are comparatively presented. In order to simulate the realistic ground condition in where the WIG craft is flying, moving ground is implemented by a conveyor belt rotating with the same velocity of the inflow. We consider two different wings (NACA0012 and DHMTU section) which have four different aspect ratios (0.5, 1.0, 1.5 and 2.0). Forces acting on the wings are measured and lift characteristics are elaborately investigated for various different conditions. In addition, end-plate effects are estimated. Results are validated by comparing with theoretic solutions of the symmetric airfoil. Present results show that ground effects are differently generated in moving or fixed ground conditions, and hence left characteristics are affected by the ground condition. Consequently, accurate aerodynamic forces acting on the WIG craft are guaranteed in a realistic moving ground condition.
Development of Model Test Methodology of Pack Ice in Square Type Ice Tank
Cho, Seong-Rak ; Yoo, Chang-Soo ; Jeong, Seong-Yeob ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 390~395
DOI : 10.3744/SNAK.2011.48.5.390
The main purpose of ice model basin is to assess and evaluate the performance of the Arctic ships and offshore structures because the full-scale tests in ice covered sea are usually very expensive and difficult. There are various ice conditions, such as level ice, brash ice, pack ice and ice ridge, in the real sea. To estimate their capacities in ice tank accurately, an appropriate model ice sheet and prepared ice conditions copied from actual sea ice conditions are needed. Pack ice is a floating ice that has been driven together into a single mass and a mixture of ice fragments of varying size and age that are squeezed together and cover the sea surface with little or no open water. So Ice-class vessels and Icebreaker are usually operated in pack ice conditions for the long time of her voyage. The most ice model tests include the pack ice test with the change of pack ice concentration. In this paper, the effect of pack ice size and channel breadth in pack ice model test is conducted and analyzed. Also we presented some techniques for the calculation of pack ice concentration in the model test. Finally, we developed a new model test methodology of pack ice condition in square type ice tank.
A Study on the Characteristics of an Air Cavity Attached Under a Flat Plate
Kim, Jong-Hyun ; Oh, Jae-Young ; Seo, Dae-Won ; Lee, Seung-Hee ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 396~403
DOI : 10.3744/SNAK.2011.48.5.396
The concept of an air lubrication has long been an object of attention since it can be utilized to reduce the frictional resistance, and what is more, it is eco-friendly. The present study examines the basic characteristics of an air cavity with intention of applying the air lubrication technology to the reduction of the resistance of a ship without excessive power increment. For the purpose, an air cavity was created at the bottom of a flat plate by injecting air behind a backward step and the hydrodynamic properties of the air cavity and the surrounding flow has been investigated experimentally and numerically. The influence of the step height and the air flow rate have been more carefully studied since they are presumed to be the main parameters affecting the characteristics of an air cavity. The results indicates that the shapes of the air cavities attached on the flat plate become "U" or "V" type depending on the incoming flow velocity and air flow rate. The study also confirms that the length of the air cavity increases with increase in air flow rate but there is a certain critical limit in the flow rate above which increase in the air cavity length is no more evident.
Simplified Vulnerability Assessment Procedure for the Warship Based on the Vulnerable Area Approach
Kim, Kwang-Sik ; Lee, Jang-Hyun ; Hwang, Se-Yun ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 404~413
DOI : 10.3744/SNAK.2011.48.5.404
It is important to assess and improve the warship survivability for the weapon threats which have a critical effect on warship. The survivability of the warship is defined as the capability of a warship to avoid or withstand a man-made hostile environment. The survivability of the warship consists of three categories (Susceptibility, Vulnerability and Recoverability). Firstly, the susceptibility is defined as the inability of a warship to avoid radars, guns, missiles and etc. Secondly, the vulnerability is defined as the inability of a warship to withstand the man-made hostile environment. Finally, the recoverability is defined as the ability of a warship to recover the damaged components and systems. Among them, this paper has described the vulnerability assessment for the hypothetical system which is composed of critical components. Also, the procedure which is suggested to calculate the vulnerable probability of the damaged warship is based on the Vulnerable Area Method.
Formation of Coherent Vortices in Late Wake Downstream of an Object in Weakly Stratified Fluid
Lee, Sung-Su ; Kim, Hak-Sun ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 414~420
DOI : 10.3744/SNAK.2011.48.5.414
Decades of studies of geophysical flow have unveiled that the flow downstream of obstacles in stratified flow consists of attached wake and strong gravity waves, or separated, fluctuating wake and persistent late wakes. Among unique and interesting characteristics of the stratified flow past obstacles is the generation of coherent vortex in the late wake far downstream of the object. Unlike in homogeneous fluid, the flow field downstream self-develops coherent vortex even after diminishing of the near wake, no matter how small the stratification is. This paper present a computational approach to simulate the generation of the coherent vortex structure in the late wake of a moving sphere submerged in weakly stratified fluid. The results are in consistent with several experimental observations and the vortex stretching mechanism is employed to explain the process of coherence.
A Study on the Speed Sea Trial on the Ice Field for Ice Breaking Research Vessel "Araon"
Kim, Hyun-Soo ; Lee, Chun-Ju ; Jeong, Seong-Yeob ; Choi, Kyung-Sik ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 421~425
DOI : 10.3744/SNAK.2011.48.5.421
To know the speed performance of "ARAON" in Arctic ice field, the measurement of ice properties which is ice thickness & strength, snow depth and free board were performed on July 2010. The measuring method of nautical signals such as heading angle, power of engine, wind & current information etc. was described in this paper. The speed sea trials in ice were performed on the four different positions with different ice properties and engine powers because the uniform level ice is not detected in the Chukchi Sea. The test field was partially constrained ice floe with hummocks and it was superposed with small broken ice pieces each other. All of the measured ice properties were compared and evaluated according to the results of sea trial. The relations between speed, ice thickness, strength and power were summarized. Consequently according to the sea trial results, the speed of ARAON is 2.78knots at the 2.49m ice thickness with 6.55MW engine power.
A Development of the Ship Weight Estimating Method by a Statistical Approach
Cho, Yong-Jin ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 426~434
DOI : 10.3744/SNAK.2011.48.5.426
Accurate weight prediction methods are an essential of the ship design in both ship cost managements and performance satisfactions. When no parent or similar ships are available, an adequate method of the ship weight estimating is required. In this study, there was carried out to develop the ship weight estimating method for the preliminary design phase. The weight estimating methods were first surveyed by the references and summarized their characteristics. The weight estimation method by statistical approach was developed for the container ship because the containerized transportation markets is gradually growing and ship's size and loading capacity are rapidly enlarged. The correlation analysis and the multiple regression analysis were used for developing the weight estimating method. As a results of evaluating the developed method, the error ratio of the variation between estimated weight and ship's data was about 5%. And it was only 1% difference with the calculating weight of conceptual design results by shipyard design team that the estimating weight of ultra-large container ship was predicted by the developed method.
Structural Assessment of the Optimal Section Shape of FRP Based Stiffeners
Jeong, Han-Koo ; Nho, In-Sik ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 435~444
DOI : 10.3744/SNAK.2011.48.5.435
This paper deals with the structural assessment of metallic and non-metallic stiffened/monocoque plated marine structures under a lateral pressure load to identify appropriate combination of material and section configuration, especially at the preliminary marine structural design stage. A generic rectangular plated structure is exemplified from the metallic superstructure of a marine vessel and its structural topology is varied for the structural assessment. In total 13 different structural topologies are proposed and assessed using appropriate elastic solutions in conjunction with a set of stress and deflection limits obtained from practice. The geometry dimensions and weights of the structural topologies are calculated, and subsequently, the costs of the materials used in the structural topologies are reviewed to discuss the cost-effectiveness of the materials. Finally, conclusions are made with the aim of suggesting suitable structural topology for the marine structural member considered in this paper.
A Construction of Aerodynamic Force Measurement System for Wind Tunnel Test of Yacht Sail and Aerodynamic Forces Measurement of Model Sail
Kim, Choul-Hee ; Choi, Jung-Kyu ; Kim, Hyoung-Tae ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 445~450
DOI : 10.3744/SNAK.2011.48.5.445
In order to estimate a yacht sail performance, measuring system of aerodynamic forces acting on the yacht sail is constructed and experiments of flexible model sail are carried out at the medium-size subsonic wind tunnel of Chungnam National University. Experimental results for a flexible sail are compared with experimental and numerical results of fixed shape sail. In case of a fixed shape sail, lift and drag coefficients are rarely changed at all velocity conditions. However, those of the flexible sail are decreased as the incoming velocity is increased. These are understandably resulted from shape variations due to the flexible material. Therefore aero-elastic similarity should be more carefully considered in the model test rather than other similarities.
A Study on Simplified Sloshing Impact Response Analysis for Membrane-Type LNG Cargo Containment System
Nho, In-Sik ; Ki, Min-Seok ; Kim, Sung-Chan ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 451~456
DOI : 10.3744/SNAK.2011.48.5.451
To ensure structural integrity of membrane type LNG tank, the rational assessment of the sloshing impact responses of tank structures should be preceded. The sloshing impact pressures acting on the insulation system of LNG tank are typical irregular loads and the resulting structural responses show very complex behaviors accompanied with fluid structure interaction. So it is not easy to estimate them accurately and immense time consuming calculation process would be necessary. In this research, a simplified method to analyse the dynamic structural responses of LNG tank insulation system under pressure time histories obtained by sloshing model test or numerical analysis was studied. The proposed technique based on the concept of linear combination of the triangular response functions which are the transient responses of structures under the unit triangular impact pressure acting on structures. The validity of suggested method was verified through the example calculations and applied to the dynamic structural response analysis of a real Mark III membrane type insulation system using the sloshing impact pressure time histories obtained by model test.
Study on the Correction Method of Ice Strength and Thickness Applied to the Sea Trial Condition Based on the Ice Model Test Results
Lee, Seung-Ki ; Kim, Moon-Chan ; Lee, Won-Jun ; Kim, Hyun-Soo ; Lee, Chun-Ju ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 457~464
DOI : 10.3744/SNAK.2011.48.5.457
This paper deal with the validation of correction method of ice strength and thickness to the sea trial condition based on the ice model test results. It is very difficult to conduct the model test corresponding to the sea trial condition exactly. In addition, the available sea trial data is not sufficient for the validation of correction method. In the present study, the model test results of Terry-Fox ice breker have been used to compare the corrected results of sea trial test by varying its thickness and strength of model ice. The HSVA and ITTC methods have been applied to the present comparisions and the required power has been also validated by using the HSVA method. There are rather good agreement between the sea trial result and model test corrected by the HSVA and ITTC method. The more comparisons are expected to be carried out in near future.
Prediction of Maneuverability of KCS Using Captive Model Test
Shin, Hyun-Kyoung ; Choi, Si-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 465~472
DOI : 10.3744/SNAK.2011.48.5.465
Recently, ultra large scale of ship is being ordered continuously and because of that, the accurate prediction of ship maneuverability in design stage becomes important matter. The model test like PMM test or CFD analysis are representative methods for predicting the maneuverability of ship. In this study, the captive model tests were carried out for predicting maneuverability of MOERI container ship(KCS) which is opened to the public using X-Y Carriage of Ocean Engineering Wide Tank of University of Ulsan. Considering the dimensions of tank, 2m class model ship was used for captive model test. CMT(Circular Motion Test) was performed for obtaining purer hydrodynamic coefficients related to yawing velocity. For getting hydrodynamic coefficients which cannot be obtained using CMT, PMM test(Planar Motion Mechanism test) were also performed. The maneuverability prediction results by simulation are compared with those of other research institutes.
A Study on the Weld-Induced Deformation and Residual Stress Analysis at FPSO Moon Pool Structure
Han, Sung-Woo ; Lee, Joo-Sung ; Kim, Sang-Il ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 5, 2011, Pages 473~478
DOI : 10.3744/SNAK.2011.48.5.473
Welding process generates distortion and residual stress in the weldment due to rapid heating and cooling. Welding distortion and residual stress in the welded structure result in many troubles such as dimensional inaccuracies in assembling and safety problem during service. The accurate prediction of welding residual stress is thus very important to improve the quality of weldment and find the way to reduce itself. This paper presents the simulation of welding-induced residual stress analysis to examine the cause of cracking in the SUS-overlay welding specimen at FPSO Moon Pool structure.