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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Naval Architecture and Ocean Engineering
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The Society of Naval Architects of Korea
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Volume & Issues
Volume 1, Issue 2 - Dec 2009
Volume 1, Issue 1 - Sep 2009
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Aerodynamic characteristics of NACA 4412 airfoil section with flap in extreme ground effect
Ockfen, Alex E. ; Matveev, Konstantin I. ;
International Journal of Naval Architecture and Ocean Engineering, volume 1, issue 1, 2009, Pages 1~12
DOI : 10.3744/JNAOE.2009.1.1.001
Wing-in-Ground vehicles and aerodynamically assisted boats take advantage of increased lift and reduced drag of wing sections in the ground proximity. At relatively low speeds or heavy payloads of these craft, a flap at the wing trailing-edge can be applied to boost the aerodynamic lift. The influence of a flap on the two-dimensional NACA 4412 airfoil in viscous ground-effect flow is numerically investigated in this study. The computational method consists of a steady-state, incompressible, finite volume method utilizing the Spalart-Allmaras turbulence model. Grid generation and solution of the Navier-Stokes equations are completed using computer program Fluent. The code is validated against published experimental and numerical results of unbounded flow with a flap, as well as ground-effect motion without a flap. Aerodynamic forces are calculated, and the effects of angle of attack, Reynolds number, ground height, and flap deflection are presented for a split and plain flap. Changes in the flow introduced with the flap addition are also discussed. Overall, the use of a flap on wings with small attack angles is found to be beneficial for small flap deflections up to 5% of the chord, where the contribution of lift augmentation exceeds the drag increase, yielding an augmented lift-to-drag ratio.
Transient effects of tendon disconnection on the survivability of a TLP in moderate-strength hurricane conditions
Kim, Moo-Hyun ; Zhang, Zhi ;
International Journal of Naval Architecture and Ocean Engineering, volume 1, issue 1, 2009, Pages 13~19
DOI : 10.3744/JNAOE.2009.1.1.013
The primary objective of this paper is to investigate the dynamic stability and survivability of a four-column classic TLP (tension-leg platform) under less-than-extreme storm conditions where one or more tendons have been lost due to damage or disconnect. The transient responses of the platform and tendon tensions at the moment of disconnection are particularly underscored. The numerical simulation is based on the BE-FE hybrid hull-tendon-riser coupled dynamic analysis in time domain. Compared to the common industry practice of checking the system without a failed tendon in the beginning, the maximum tension on the neighboring tendon can be significantly increased at the moment of disconnection due to the snap-like transient effects, which can lead to unexpected failure of the total system. It is also found that the transient effects can be reduced with the presence of TTRs (top-tensioned risers) with pneumatic tensioners. It is also seen that the TLP cannot survive in the 100-yr hurricane condition after losing one tendon.
Three dimensional numerical simulations for non-breaking solitary wave interacting with a group of slender vertical cylinders
Mo, Weihua ; Liu, Philip L.F. ;
International Journal of Naval Architecture and Ocean Engineering, volume 1, issue 1, 2009, Pages 20~28
DOI : 10.3744/JNAOE.2009.1.1.020
In thus paper we validate a numerical model for wave-structure interaction by comparing numerical results with laboratory data. The numerical model is based on the Navier-Stokes (N-S) equations for an incompressible fluid. The N-S equations are solved by a two-step projection finite volume scheme and the free surface displacements are tracked by the volume of fluid (VOF) method The numerical model is used to simulate solitary waves and their interaction with a group of slender vertical piles. Numerical results are compared with the laboratory data and very good agreement is observed for the time history of free surface displacement, fluid particle velocity and wave force. The agreement for dynamic pressure on the cylinder is less satisfactory, which is primarily caused by instrument errors.
Study on the Contra-Rotating Propeller system design and full-scale performance prediction method
Min, Keh-Sik ; Chang, Bong-Jun ; Seo, Heung-Won ;
International Journal of Naval Architecture and Ocean Engineering, volume 1, issue 1, 2009, Pages 29~38
DOI : 10.3744/JNAOE.2009.1.1.029
A ship's screw-propeller produces thrust by rotation and, at the same time, generates rotational flow behind the propeller. This rotational flow has no contribution to the generation of thrust, but instead produces energy loss. By recovering part of the lost energy in the rotational flow, therefore, it is possible to improve the propulsion efficiency. The contra-rotating propeller (CRP) system is the representing example of such devices. Unfortunately, however, neither a design method nor a full-scale performance prediction procedure for the CRP system has been well established yet. The authors have long performed studies on the CRP system, and some of the results from the authors' studies shall be presented and discussed.
Mechanical properties of friction stir welded aluminum alloys 5083 and 5383
Paik, Jeom-Kee ;
International Journal of Naval Architecture and Ocean Engineering, volume 1, issue 1, 2009, Pages 39~49
DOI : 10.3744/JNAOE.2009.1.1.039
The use of high-strength aluminum alloys is increasing in shipbuilding industry, particularly for the design and construction of war ships, littoral surface craft and combat ships, and fast passenger ships. While various welding methods are used today to fabricate aluminum ship structures, namely gas metallic arc welding (GMAW), laser welding and friction stir welding (FSW), FSW technology has been recognized to have many advantages for the construction of aluminum structures, as it is a low-cost welding process. In the present study, mechanical properties of friction stir welded aluminum alloys are examined experimentally. Tensile testing is undertaken on dog-bone type test specimen for aluminum alloys 5083 and 5383. The test specimen includes friction stir welded material between identical alloys and also dissimilar alloys, as well as unwelded (base) alloys. Mechanical properties of fusion welded aluminum alloys are also tested and compared with those of friction stir welded alloys. The insights developed from the present study are documented together with details of the test database. Part of the present study was obtained from the Ship Structure Committee project SR-1454 (Paik, 2009), jointly funded by its member agencies.
Some practical design aspects of appendages for passenger vessels
Jang, Hag-Soo ; Lee, Hwa-Joon ; Joo, Young-Ryeol ; Kim, Jung-Joong ; Chun, Ho-Hwan ;
International Journal of Naval Architecture and Ocean Engineering, volume 1, issue 1, 2009, Pages 50~56
DOI : 10.3744/JNAOE.2009.1.1.050
The hydrodynamic effect of appendages for high-speed passenger vessels, such as Ro-Pax, Ro-Ro and cruiser vessels, is very severe and, therefore, it is essential to carry out the design of appendages for high-speed passenger vessels from the preliminary design stage to the final detail design stage through a full survey of the reference vessels together with sufficient technical investigation. Otherwise, many problems would be caused by mismatches between the appendages and the hull form. This paper investigates the design characteristics of some appendages, such as the side thruster, the shaft-strut, and the stern wedge, based on the design experience accumulated at Samsung, on CFD, and on model test results for high-speed passenger vessels. Further to this investigation, some practical and valuable design guidelines for such appendages are suggested.