• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1003-1012
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• 2008

A three dimensional numerical study has been applied to predict the turbulent fluid flow and heat transfer characteristics for the rectangular channel with different types of baffles. Four different types of the baffles are used. The inclined baffles have the width of 19.8 cm, the square diamond type hole having one side length of 2.55 cm, and the inclination angle of $5^{\circ}$. Reynolds number is varied between 23,000 and 57,000. The SST k-${\omega}$ turbulence model is used in the present numerical study. The validity of the numerical results is examined with the experimental data. The numerical results of the flow field depict that the flow patterns around the different baffle type are entirely different and it significantly affects the local heat transfer characteristics. The heat transfer and friction factor depend significantly on the number of baffle holes. It is found that the heat transfer enhancement of baffle type II (3 hole baffle) has the best values.

• 동력기계공학회지
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• 제17권5호
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• pp.30-37
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• 2013

For vessels operating in the cold climate regions, the ballast water inside or hopper tanks above the waterline may be frozen, starting at the top of the tank and at the side walls. Therefore, countermeasures against freeze-up of the ballast tank such as air-bubbling system, hot steam injecting system, heating coil system and water circulating system are taken to prevent freeze-up phenomenon; however, there are no rigorous investigations of anti-freezing to examine the effectiveness and validity of systems against freeze-up of the ballast tank, in which the temperatures are about -$25^{\circ}C$ (ambient air temperature) and $0^{\circ}C$ (sea water), respectively. In this paper, to ensure reasonable specifications for cold regions if the measures from the above-mentioned systems against freeze-up are effective, the phenomenon of ballast tank freeze-up is simulated and discussed in low temperature conditions. With the results using the commercial CFD code, CFX 14, the most cost-effective solution is conducted to prevent being frozen along the outer surface.

• 한국CDE학회논문집
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• 제19권1호
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• pp.41-49
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• 2014

For the reuse of the existing 3D block model of a ship, we analyze the hull modeling process using AVEVA Marine which is a representative CAD (Computer-Aided Design) system for the shipbuilding. In the AVEVA Marine environment where the design engineer makes 3D model on the 2D view that is so-called 2.5D, it cannot be possible to copy to reuse the block model just simply copying the 3D feature model itself like in the general mechanical CAD system or Smart Marine 3D which are on the basis of the 3D model representation. In this paper, we analyze the scheme file where the 3D model is defined in AVEVA Marine so that we develop the program for the block copy and the translation using this scheme file. It is significant that this program can be immediately available as a real-world application on the AVEVA Marine environment.

• Journal of Advanced Marine Engineering and Technology
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• 제38권3호
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• pp.318-324
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• 2014

선원대피처는 해적의 승선침입이 임박한 상황에서 모든 선원이 피난할 목적으로 본선 내부에 지정 설치된 장소로서 해적의 침입시도에 일정기간 동안 버틸 수 있는 구조로 만들어져야한다. 국내외 규정에 따라 선박의 은밀한 장소에 설치되는 선원 대피처는 중화기로 무장한 소말리아 해적으로부터 선원들의 안전을 확보하는 데에 필요한 최후의 보루가 되고 있다. 본 연구에서는 선원 대피처에 관련된 국내외 규정에 대한 검토와 고찰을 통하여 현행 규정에 따른 선원대피처의 한계, 취약점 등을 식별하고, 우리나라 선박설비기준의 요건을 중심으로 향후 보다 안전하고 적용 가능한 개선 방안을 제시하였다.

• 대한조선학회지
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• 제25권2호
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• pp.19-30
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• 1988

Sectional added masses of an elastic beam vibrating vertically on the free surface in higher harmonic modes are evaluated. Hydrodynamic interactions between neighboring sections, which strip theory ignores, are considered for modal wave lengths of the order of magnitude of cross-sectional dimensions of the body. An approximate solution of modified Helmholtz equation which becomes a singular perturbation problem at small wave lengths is secured to get an analytic expression for added masses attending higher harmonic modes. As a bound of the present theory, the modified Helmholtz equation is solved for the long flat plate vibrating at high frequency on the water surface without any limitations on modal frequency. Finally, extensive series of numerical calculations are carried out for ship-like forms. It is found that when modal wave length is comparable to or shorter than a typical cross-sectional dimension of a body, sectional interaction effects are large which result in considerable reductions in added masses. For a fuller section, the ratio of added mass reduction is greater. In the limit of vanishing sectional area, the added masses approach to that of flat plate of equal beam. It is shown that the added mass distribution for a Legendre modal from can be determined form the present theory and that the results agree with the extensive three-dimensional determination of Vorus and Hilarides.

• 대한조선학회논문집
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• 제41권6호
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• pp.48-55
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• 2004

Loads on offshore structures are largely transferred to the bracing members in the form of axial forces. The detrimental effects of imperfections on compressive strength are well recognized. Damage in the members of offshore structures would significantly affect the compressive behavior of the members. As a result, such damages may also affect the ability of the structure to withstand the functional and environmental loads. It is important to be able to assess the residual strength of damaged members quickly and accurately. This will help operators to make the decision whether the member has to be repaired or not. In this study, a series of calculation is performed to study the effects of different parameters on the behavior of such damaged members under axial load. And the results of analysis are compared with those of experiment.

• 대한조선학회논문집
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• 제48권1호
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• pp.33-41
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• 2011

For the assessment of ultimate longitudinal strengths of damaged hull girders, it is preliminarily necessary to determine the extents and locations of the damages due to severe accidents. This paper deals with the estimation of the damages from collisions and groundings of large-sized vessels where deterministic and probabilistic approaches are investigated. Deterministic damages estimated from MARPOL(or ICLL), ABS and DNV are compared with probabilistic damages from IMO guideline and some references including damage statistic data. Damages from MARPOL show largest one among all the investigated damage estimation, since it was developed not for the residual strength of hull girder but for the damage stability calculation. IMO guideline with high level probability of damage(eg. 95% probability level) also forecasts even severer damage extents than MARPOL. On the other hand, assuming average probability level of damage, the calculated damage sizes are around the one from deterministic approaches.

• 대한조선학회논문집
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• 제47권4호
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• pp.598-605
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• 2010

The structural design of oil tankers and bulk carriers should be performed based on the Common Structural Rules(CSR) which were recently established by the International Association Classification Societies(IACS). At first, in the structural design viewpoint, the scantling and hullweight based on the CSR should be compared with those of existing rules, and then a minimum weight/cost design should be performed by considering the variation of the number of web and the material property. In this study, the optimum web space and material property will be proposed by performing a minimum weight/cost design of a large oil tanker, and the results will be compared with those of existing ship. The longitudinal members are determined by SeaTrust-Holdan developed by the Korean Register of Shipping(KR), and the transverse members are determined by NASTRAN and PULS.

• Journal of Ship and Ocean Technology
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• 제12권1호
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• pp.1-15
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• 2008

An edgetone is the discrete tone or narrow-band sound produced by an oscillating free shear layer, impinging on a rigid surface. In this paper, 2-dimensional edgetone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle is presented using lattice Boltmznan model with 21 bits, which is introduced a flexible specific heat ratio y to simulate diatomic gases like air. The blown jet is given a parabolic inflow profile for the velocity, and the edges consist of wedges with angle 20 degree (for symmetric wedge) and 23 degree (for inclined wedge), respectively. At a stand-off distance w, the edge is inserted along the centerline of the jet, and a sinuous instability wave with real frequency is assumed to be created in the vicinity of the nozzle exit and to propagate towards the downward. Present results presented have shown in capturing small pressure fluctuating resulting from periodic oscillation of the jet around the edge. The pressure fluctuations propagate with the speed of sound. Their interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips. It is found that, as the numerical example, satisfactory simulation results on the edgetone can be obtained for the complex flow-edge interaction mechanism, demonstrating the capability of the lattice Boltzmann model with flexible specific heat ratio to predict flow-induced noises in the ventilating systems of ship.

• Corrosion Science and Technology
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• 제12권5호
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• pp.239-244
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• 2013

Marine equipment exposed to harsh environments requires not only excellent corrosion resistance but also improvement of physical characteristics against natural material degradation. With growing interests in ocean energy resources, the higher reliability for marine equipment has become more important in terms of material characteristics. ALBC3 alloy represents excellent corrosion resistance and is widely used in corrosive environments. However, cavitation damage occurs frequently due to its poor durability in high flow rate of marine environment. In this research, shot peening technology was employed as a surface modification with shot peening stand-off distance to mitigate cavitation damage. The effects of shot peening on extent of cavitation damage and weight loss were evaluated for both shot peened and non-peened specimens. The results revealed that the application of shot peeing decreased cavitation damage for all experimental conditions in comparison with the non-peened specimens. The optimum stand-off distance was determined to be 10 cm, since more than 35 % of cavitation damage reduction was observed.