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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 52, Issue 6 - Dec 2015
Volume 52, Issue 5 - Oct 2015
Volume 52, Issue 4 - Aug 2015
Volume 52, Issue 3 - Jun 2015
Volume 52, Issue 2 - Apr 2015
Volume 52, Issue 1 - Feb 2015
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Lug Arrangement and Dynamic Analysis of Lifting Simulation for Underwater Installation of Structure in Asymmetric Position
Jo, A-Ra ; Park, Kwang-Phil ; Lee, Hyun-Jin ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 283~289
DOI : 10.3744/SNAK.2015.52.4.283
RGT(Riser Guide Tube) is a part of mooring on the bottom of a turret system to be connected with a production riser, and DBSC(Diverless Bend Stiffener Connector) is a latching component between them. In this paper, appropriate lug arrangement is decided mathematically for the case that a DBSC is lifted and installed on a RGT under the water while FPSO is under construction. Considering asymmetric arrangement & position of RGT and initial lug position, additional lug positions are determined by using an optimization method. The modified installation scheme with new lug points is investigated with a lifting simulation system, SIMSON. The simulation result shows that the installation of DBSC on RGT under the given conditions is quite feasible; therefore the mathematical method is proven to be appropriate.
Added Resistance and Seakeeping Ability of a Medium-sized Passenger Ship with Gooseneck Bulb
Yu, Jin-Won ; Lee, Young-Gill ; Ha, Youn-Jin ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 290~297
DOI : 10.3744/SNAK.2015.52.4.290
This research is focusing on the added resistance and seakeeping ability of the designed passenger ship with gooseneck bulb(Designed hull) which provide the improvement of resistance performance under calm water condition. By comparing the added resistances and seakeeping abilities of the reference hull and the designed hull form with gooseneck bulb, it is confirmed that there is little difference in the operational comfort and the reduction of ship speed. As a result, the applied gooseneck bulb in this study is verified for the applicability to medium-sized passenger ships with a good resistance performance.
Optimal Arrangement of Resilient Mount installed on Frame Support Structure at Shipboard Equipment under Shock Load
Ji, Yong Jin ; Kwak, Jeong Seok ; Lee, Hyun Yup ; Kim, Sung Chan ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 298~304
DOI : 10.3744/SNAK.2015.52.4.298
Shipboard equipment in naval ships should be designed to be safe under the shock load. Very high stress due to the shock load can be effectively reduced by the resilient mounts considering the mount capacity and dynamic characteristics. An optimum arrangement of resilient mount installed to absorb the shock energy is addressed to assess the safety of ship structure and shipboard equipment subjected to the shock load. Structural responses are analyzed for both frame structure supporting the shipboard equipment subject to the shock load with and without the resilient mounts. The shock absorbability of the resilient mount is evaluated by the results of structural response analysis; meanwhile, several types of shock analyses considering the arrangement of resilient mounts are carried out and the shock responses are compared to verify the effect of the arrangement. Thereafter, optimum arrangements are obtained by means of Genetic algorithm (GA) considering the different capacities of resilient mount. Stress, deformation and dynamic feature at the frame structure supporting the shipboard equipment under the shock load are also discussed in order to meet the capacity of resilient mount.
Numerical Analysis of the Drag of Conical Cavitators
Kim, Hyoung-Tae ; Lee, Hyun-Bae ; Cho, Jung-Kyu ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 305~314
DOI : 10.3744/SNAK.2015.52.4.305
In this paper, a numerical analysis is carried out to study the drag of conical cavitators, supercavity generation devices for the high-speed underwater vehicle. The realizable k-∊ turbulence model and the Schnerr-Sauer cavitation model are applied to calculate steady-state supercavitating flows around cones of various cone angles. The calculated drags of the cones are decomposed of the pressure and the friction parts and their dependency on the geometry and the flow conditions have been analyzed. It is confirmed that the pressure drag coefficients of the cones can be estimated by a simple function of both the cone angle and the cavitation number while the friction drag coefficients approximately by well-known empirical formulas, e.g., Schults-Grunow's for the drag of the flat plate. Finally a practical method for estimating the total drags of supercavitating cones is suggested, which can be useful consequently for the design of conical cavitaors.
The Effective Young's Modulus of Model Ice Sheet in Ice Basin
Lee, Jae-Hwan ; Choi, Bong-Kyun ; Kim, Tae-Wan ; Lee, Chun-Ju ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 315~322
DOI : 10.3744/SNAK.2015.52.4.315
In this paper, the theory of rectangular plate on the elastic foundation is used to get the relation equation between the effective Young’s modulus and the ice sheet deflection by applying the characteristic length concept, since the model ice sheet is rectangular shape in KRISO (Korea Research Institute for Ships and Ocean Engineering) ice basin. The obtained relation equation is equal to that of using the circular plate theory. A device is made and used to measure the deflection of ice plate using LVDT (Linear Variable Differential Transformer) for several loading cases and the procedure of experiments measuring the deflection used for getting the Young’s modulus is explained. In addition, the flexural strength value obtained through flexural strength experiments is compared with that of finite element analysis using the obtained effective Young’s modulus. Also, a nonlinear FEA (Finite Element Analysis) of cantilever ice beam is done with eroding effect and LS-DYNA result shows the fracture of brittle ice under 1 mm/s velocity load.
A Study on the De-Icing Performance Evaluation and Design Guide for Ice Class Louver of the Vessels Operating in Cold Region
Jung, Young-Jun ; Seo, Young-Kyo ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 323~329
DOI : 10.3744/SNAK.2015.52.4.323
For the design guide of a vessel operating in cold region, numerical analysis was carried out to evaluate the ice class louver which installed the heating cables by using ANSYS 13.0 CFX. The numerical analysis was performed by considering Unsteady Reynolds Averaged Navier Stokes (RANS) equation. This study based on the experimental results of ‘The Cryogenic Performance Evaluation for the Excellent De-icing Ice Class Louver’ in KRISO. For validation of the numerical analysis results, the cold chamber experimental data measured by the heat sensors in certain location of the ice class louver was used. The external environmental temperature which varies from 0℃ to –30℃ was considered in numerical analysis. Also the design guide for optimum de-icing presented through heating cable power capacity(33 W/m, 45 W/m, 66 W/m), location of the heating cable(front, center, behind on the blade) and relative velocity(1 m/s, 4 m/s, 7 m/s).
Examination of Modeling Methods for Tower Crane Transportation using Multibody Dynamics
Jo, A-Ra ; Park, Kwang-Phil ; Lee, Chul-Woo ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 330~337
DOI : 10.3744/SNAK.2015.52.4.330
When a tower crane is carried by a transporter in shipyard, the height and length of the tower crane should be adjusted to meet the safety guidelines. Since the guidelines came from the field experience, the safety limitation needs to be analyzed by a computer simulation. In this paper, modeling methods are addressed to implement the appropriate transportation simulation of a tower crane. For the relation between the tower crane and the transporter, normal contact force, friction force, and kinematic constraints are compared. Assignment of relevant linear acceleration and angular velocity is considered for the transporter to start or move on an inclined ground surface. By using the examined modeling methods, the dynamic motion of tower crane transportation is analyzed by a dynamic simulation program, and comparison between the simulation result and analytic solution is made to verify the feasibility of the modeling methods.
Analysis of Added Resistance in Short Waves
Yang, Kyung-Kyu ; Seo, Min-Guk ; Kim, Yonghwan ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 338~348
DOI : 10.3744/SNAK.2015.52.4.338
In this study, the added resistance of ships in short waves is systematically studied by using two different numerical methods - Rankine panel method and Cartesian grid method – and existing asymptotic and empirical formulae. Analysis of added resistance in short waves has been preconceived as a shortcoming of numerical computation. This study aims to observe such preconception by comparing the computational results, particularly based on two representative three-dimensional methods, and with the existing formulae and experimental data. In the Rankine panel method, a near-field method based on direct pressure integration is adopted. In the Cartesian grid method, the wave-body interaction problem is considered as a multiphase problem, and volume fraction functions are defined in order to identify each phase in a Cartesian grid. The computational results of added resistance in short waves using the two methods are systematically compared with experimental data for several ship models, including S175 containership, KVLCC2 and Series 60 hulls (C
= 0.7, 0.8). The present study includes the comparison with the established asymptotic and empirical formulae in short waves.
Nonlinear Finite Element Analysis for Ultimate Hull Girder Strength of Container Ship
Yeom, Cheol Wung ; Moon, Jeong Woo ; Nho, In Sik ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 349~355
DOI : 10.3744/SNAK.2015.52.4.349
Through the recent accident, the checking of ultimate hull girder capacity for container ship should be needed. Smith’s method is well known as the only simplified method to access rapidly for ultimate hull girder capacity except very expensive nonlinear F.E approach. This simplified method, however, is admitted to apply only to bulker and tanker in accordance with Classification Rules up to now. The targets of this study are to verify effectiveness of the simplified method for container ship’s ultimate hull girder strength and to propose the safety factor considering the local bending in double bottom structures due to out of plane loads through the nonlinear F.E analyses. Two different sized ships and three loading conditions which are pure bending, homo-loading and one-bay empty condition were used for this study. Based on the F.E results, the present study showed that CSR’s simplified method is available for the ultimate hull girder strength of container ship and over 1.2 of safety factor should be applied to consider the local bending effect in double bottom structures due to out of plane loads such as sea pressure an cargo.
Visualization of Microbubbles Affecting Drag Reduction in Turbulent Boundary Layer
Paik, Bu-Geun ; Yim, Geun-Tae ; Kim, Kwang-Soo ; Kim, Kyoung-Youl ; Kim, Yoo-Chul ;
Journal of the Society of Naval Architects of Korea, volume 52, issue 4, 2015, Pages 356~363
DOI : 10.3744/SNAK.2015.52.4.356
Microbubbles moving in the turbulent boundary layer are visualized and investigated in the point of frictional drag reduction. The turbulent boundary layer is formed beneath the surface of the 2-D flat plate located in the tunnel test section. The microbubble generator produces mean bubble diameter of 30 – 50 μm. To capture the micro-bubbles passing through the tiny measurement area of 5.6 mm
to 200 mm
, the shadowgraphy system is employed appropriately to illuminate bubbles. The velocity field of bubbles reveals that Reynolds stress is reduced in the boundary layer by microbubbles’ activity. To understand the contribution of microbubbles to the drag reduction rate more, much smaller field-of-view is required to visualize the bubble behaviors and to find the 2-D void fraction in the inner boundary layer.