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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
Selecting the target year
Study on Effective Arrangement of Main Engine Top-Bracing
Choung, Joon-Mo ; Min, Dug-Ki ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 289~298
DOI : 10.3744/SNAK.2011.48.4.289
This paper provides procedures to effectively determine arrangement of hydraulic type top-bracings, which are popular for the main engine of the mid and large sized commercial vessels. Analyzing the operation mechanism of hydraulic top-bracing, ideal unified nonlinear stiffness curve is presented for linear frequency response analysis and nonlinear transient response analysis. Nonlinear stiffnesses of the curve are determined based on the regression analysis of test results. It is noted from linear frequency response analysis, initial setting pressure is most important among the setting values of the other stiffness intervals. From transient response analyses for two top-bracing arrangement scenarios, it is recognized that, as far as initial setting pressure is well controlled for the concerning vessels, only two top-bracings are enough to suppress H-mode excitation forces from main engine.
A Study on Frequency Domain Fatigue Damage Prediction Models for Wide-Banded Bimodal Stress Range Spectra
Park, Jun-Bum ; Kang, Chan-Hoe ; Kim, Kyung-Su ; Choung, Joon-Mo ; Yoo, Chang-Hyuk ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 299~307
DOI : 10.3744/SNAK.2011.48.4.299
The offshore plants such as FPSO are subjected to combination loading of environmental conditions (swell, wave, wind and current). Therefore the fatigue damage is occurred in the operation time because the units encounter the environmental phenomena and the structural configurations are complicated. This paper is a research for frequency domain fatigue analysis of wide-band random loading focused on accuracy of fatigue damage estimation regarding the proposed methods. We selected ideal bi-modal spectrum. And comparison between time-domain fatigue analysis and frequency-domain fatigue analyses are conducted through the fatigue damage ratio. Fatigue damage ratios according to Vanmarcke`s bandwidth parameter are founded for wide-band. Considering safety, we recommend that Jiao-Moan and Tovo-Benasciutti methods are optimal way at the fatigue design for wide-band response. But, it is important that these methods based on frequency-domain unstably change the accuracy according to the material parameter of S-N curve. This study will be background and guidance for the new frequency-domain fatigue analysis development in the future.
Analysis of a Two-Dimensional Section of Deforming Yacht Sails
Lee, Hee-Bum ; Rhee, Shin-Hyung ; Yoo, Jae-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 308~316
DOI : 10.3744/SNAK.2011.48.4.308
Although a yacht sails operate with large displacement due to very thin thickness, many studies for flow around yacht sails have not considered the sail deformation. The sail deformation not only caused a change in the center of effect(CE) on the sail but also a change in the thrust of the sail. The change of the CE and thrust affects the center of lateral resistance(CLR) and side forces of the hull, and the balance of the yacht. These changes affect the motion of the yacht which changes the velocity of the yacht. Thus, when analyzing the flow around yacht sails, the sail deformation should be considered. In the present study, fluid-structure-interaction(FSI) analysis of a two dimensional section of yacht sails was performed to consider the effects of sail deformation on the lift and drag performance. FSI and moving mesh methods were studied. Computational methods were verified using benchmark test cases such as the flow around horizontal and vertical cantilever beams. Shape deformation, pressure distribution, lift forces and separation flow were compared for both rigid and deformable sail.
Analysis of Ship Squat in Confined Water Using CFD
Shin, Hyun-Kyoung ; Choi, Si-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 317~324
DOI : 10.3744/SNAK.2011.48.4.317
When a ship proceeds in confined water, like canal, the water ahead of ship is pushed by hull. This pushed water returns to the side and under the hull, and this returned water will make fluid velocity higher at the side and under the hull, compared to the case in the infinite water depth. Due to the higher velocity, the pressure under the hull will decrease, resulting in the ship drop. This phenomenon is called "ship squat" and ship squat will result in various marine accidents. In this paper, for predicting ship squat, numerical calculation was carried out using commercial CFD code, FLUENT. To confirm wave pattern profile around the ship, VOF(Volume of Fluid) method was applied. The calculated results were compared with other paper`s results and empirical methods.
Optimal Determination of Pipe Support Types in Flare System for Minimizing Support Cost
Park, Jung-Min ; Park, Chang-Hyun ; Kim, Tea-Soo ; Choi, Dong-Hoon ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 325~329
DOI : 10.3744/SNAK.2011.48.4.325
Floating, production, storage and offloading (FPSO) is a production facility that refines and saves the drilled crude oil from a drilling facility in the ocean. The flare system in the FPSO is a major part of the pressure relieving system for hydrocarbon processing plants. The flare system consists of a number of pipes and complicated connection systems. Decision of pipe support types is important since the load on the support and the stress in the pipe are influenced by the pipe support type. In this study, we optimally determined the pipe support types that minimized the support cost while satisfying the design constraints on maximum support load, maximum nozzle load and maximum pipe stress ratio. Performance indices included in the design constraints for a specified design were evaluated by pipe structural analysis using CAESAR II. Since pipe support types were all discrete design variables, an evolutionary algorithm (EA) was used as an optimizer. We successfully obtained the optimal solution that reduced the support cost by 27.2% compared to the initial support cost while all the design requirements were satisfied.
Average Compressive Strengths of Stiffened Plates for In-Service Vessels Under Lateral Pressure
Choung, Joon-Mo ; Jeon, Sang-Ik ; Lee, Min-Seong ; Nam, Ji-Myung ; Ha, Tae-Bum ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 330~335
DOI : 10.3744/SNAK.2011.48.4.330
This paper presents estimation of average compressive strengths of three types of stiffened panels under lateral pressure and axial compression based on simplified formulas from CSRs and nonlinear FEAs. FEA scenarios are prepared based on the slenderness ratios of the stiffened panels used for in-service vessels. The seven step lateral pressures by 1bar increment are imposed on FE models assuming maximum 30m water height. The number of FEAs for FB-, AB-, and TB-stiffened panels is totally 189 times. FEA results show that existence of pressure can evolves significant reduction of ultimate strengths, meanwhile CSR formulas do not take into account the lateral pressure effect. Lateral pressure acting on the stiffened panel with higher column slenderness ratio more reduces the ultimate strengths than those with smaller column slenderness ratio. A new concept of relative average compressive strain energy instead of the ultimate strength is introduced in order to rationally compare the average compressive strength through complete compressive straining regime. The differences of the ultimate strengths between CSR formulas and FEA results are relatively small for FB- and AB-stiffened panels, but larger discrepancies of relative average compressive strain energies are shown.
A Comparative Study between Measurement and Prediction Results of a Naval Ship Infrared Signature in the Marine Environment
Kim, Jung-Ho ; Yoon, Yoon-Sik ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 336~341
DOI : 10.3744/SNAK.2011.48.4.336
Ship infrared signature is the cause of detection and tracking by infrared sensor and anti-ship missile seeker. Recent warships have been applied the infrared stealth technology to reduce own ship infrared signature and tested to validate own ship infrared signature level. This study describes the two issues. Firstly, we describe the infrared measurement concept and infrared signature level establishment method that have been performed. Secondly, we compare and analyze the error components between the infrared measurement and simulation result.
On the Fatigue Analysis of Large Crane Pedestal in Drillship
Lee, Jeong-Hoon ; Lee, Joo-Sung ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 342~345
DOI : 10.3744/SNAK.2011.48.4.342
Drillship has several large cranes to handle the various equipments for drilling work. These cranes are supported by crane pedestals which are installed on main deck. Two major loads, i.e., hull girder bending moment and crane operation loading shall be considered to confirm the structural strength in way of crane pedestal. In this paper, the fatigue analysis is performed for the structures in way of crane pedestal considering two(2) loads as mentioned in the above is introduced.
A Study on the Interaction between Hull-Propeller and a High-Lifting Horn-type Rudder
Kim, Doo-Dong ; Lee, Young-Gill ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 346~356
DOI : 10.3744/SNAK.2011.48.4.346
Rudder is to be located in extremely complicated flows generated and disturbed behind a hull and a propeller in operation. In order to estimate the rudder efficiency, it is quite important to investigate the disturbed flows due to the interaction under the hull-propeller and rudder condition. The purpose of the present research is to investigate the interaction between the hull-propeller and a high-lifting horn-type rudder through both numerical computations and experiments. A horn-type rudder implementing the Coanda effect of USB (Upper Surface Blowing) type is selected for its high efficiency of lifting force, and a 1/85 scaled model of 47K PC(Product Carrier) is manufactured for the purpose of the model test. The forces acting on the rudder during the experiment are measured using a three-component force gauge. Both cases are investigated in the hull-propeller-rudder condition and rudder open-water condition, which confirms that the flows generated under the former condition is considerably different from that of the latter condition.
The Effect of Appendages of a Water-Jet Propelled High Speed Vessel on the Course Keeping Ability
Park, Han-Sol ; Kim, Dong-Jin ; Lee, Sung-Kyun ; Park, Jong-Yong ; Rhee, Key-Pyo ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 357~362
DOI : 10.3744/SNAK.2011.48.4.357
It has been often reported that a water-jet propelled high speed vessel lost the course keeping ability in seaway. In this study, model tests of a high speed vessel were performed to measure the running attitude and to check the course keeping ability. The model ship may lose the course keeping ability due to bad running attitudes such as bow drop. So model tests were carried out to improve the running attitude by changing the position of longitudinal center of gravity and using appendages at the bow and the stern of a model. The position of lateral center of pressure moved toward stern and the course keeping ability was improved by modifying the transom wedge angle.
The Measuring Methodology of Friction Coefficient between Ice and Ship Hull
Cho, Seong-Rak ; Chun, Eun-Jee ; Yoo, Chang-Soo ; Jeong, Seong-Yeob ; Lee, Chun-Ju ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 363~367
DOI : 10.3744/SNAK.2011.48.4.363
In this paper, friction coefficients between ices and model ship were studied in order to predict the resistance of ice. The friction coefficient is a dimensionless scalar value which describes the ratio of the force of friction between two bodies and the force pressing them together. The coefficient of friction depends on the materials, roughness on surface, lubrication, etc. We tested and analyzed the friction coefficient for the development of the test methodology. The friction coefficient for ice model test is very dominant to predict the ship performance, so every ice tank uses their own painting technique. In this study, the friction coefficient with changing the moving speed of ice was studies by using a flat plates which were made by the MOERI`s paining technique and the basic research for the developing the paining methodology in the MOERI ice model basin was carried out.
Global Ship Vibration Analysis by Using Distributed Fluid Added Mass at Grid Points
Kim, Young-Bok ; Choi, Moon-Gil ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 368~374
DOI : 10.3744/SNAK.2011.48.4.368
Recently, the ship vibration analysis technique has been well set up by using FEM. The methods considering the hydrodynamic added mass and damping of the fluid surrounding a floating ship have been well developed, so that they can be calculated by using the commercial package FEM programs such as MSC/NASTRAN, ADINA and ANSYS. Especially, MSC/NASTRAN has the functions to consider the fluid in tanks(MFLUID) and to solve the Fluid-Structure Interaction(FSI) problem(DMAP). In this study, the global ship vibration with considering the added mass distributed at the grid points on the wetted shell surface is introduced to. In the new method, the velocity potentials of the fluid surrounding a floating ship are calculated by solving the Lapalce equation using the Boundary Element Method(BEM), and the point mass is obtained by integrating the potentials at the points. Then, the global vibration analyses of the ship structure with distributed added mass on the wetted surface are carried out for an oil/chemical tanker. During the future sea trial, the results will be confirmed by measurement.
Design of a Cable Array Robot System
Sheen, Dong-Mok ; Lee, Youn-Am ;
Journal of the Society of Naval Architects of Korea, volume 48, issue 4, 2011, Pages 375~380
DOI : 10.3744/SNAK.2011.48.4.375
Loading/unloading at sea is necessitated as larger container ships are being used. It is also unavoidable to load/unload at sea during military operations. An experimental cable array robot system, which can be used for loading/unloading at sea, consisting of four cables operated by four motors is designed and built. Even though it has simple structure, it has a large pay-load/robot-weight ratio, flexibility and wide workspace and can be easily built at low cost. In order to plan and control the paths of end-effector, two interpolation methods are introduced and compared. Since the robot is entirely based on cable tension, an analysis of tension is also presented for monitoring and planning purpose.