• 한국항만학회지
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• 제11권1호
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• pp.121-128
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• 1997

항만공학 분야의 해양파 문제에서 자유수면파를 수치 및 실험에 의한 방법으로 해석하였다. 수치적인 방법은 자유수면 격자를 유한차분법의 이산화과정을 통해 정도(精度)를 향상시키기 위하여 나비에 스토크스 방정식의 각항에 서로 다른 형태의 격자를 적용하여 컴퓨터의 용량을 최소화하고 수렴속도를 극대화하는 것이다. 난류흐름을 재연하기 위해 Baldwin Lomax 모형을 도입하였고 대상모형은 S103 선박으로 하였다. 실험은 프루드수 0.26부터 0.30까지 수행하였고 각 속도마다 조파현상을 해석해서 수치결과와 비교하였다. 본연구는 해양파의 점성유동장 해석에서 복합격자를 사용했을때의 수치계산 결과가 실험값에 접근하고 있음을 보여주고 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1334-1338
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• 2005

A limit switch box is used for an indicator of a valve actuator. This device indicates an opening and closing of a valve or a throttle in the valve actuator. In a ship, equipments require safety and robustness because of a rough environment and a specific condition during a voyage. However, the limit switch box has been used in an indoor environment generally. This study developed a new limit switch box which can be used at an outdoor environment. This study designed the new limit switch box. The housing of the limit switch box was made by an aluminum die cast method with surface painting after anodizing or chromate coating. In order to evaluate the endurance of the housing, the endurance tests against salt water have been conducted. Experiment results showed that the proposed device provides a reliable performance against salt water.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.43-48
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• 1995

A numerical computation is carried out to analyse characteristics of flow fields around Air Supported Ships having arbitrary form. The computations are performed in a rectangular grid system with MAC(Marker And Cell) method. The governing equations are represented in a Finite Difference form by forward differencing in time and centered differencing in space except for convection terms. For validation of this numerical analysis method, the computation of flow fields around Catamaran and ACV(Air Cushion Vehicle) with pressure distribution on free surface are done, and that around Surface Effect Ship is also carried out. The results of the computations are compared with the those of existed numerical computation and experimental results with the same condition.

• 한국표면공학회지
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• 제42권1호
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• pp.34-40
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• 2009

In the study, it was carried out dissimilar metal welding on materials for Al ship. The electrochemical and mechanical characteristics evaluated for specimen welded by ROBOT. The hardness of welding zone is lower than those of heat affected zone and base metal. At the result of tensile test, the specimen welded with ER5183 welding material presented excellent property compared with ER5556. The polarization trend for the base metal and welding metal showed the effects of concentration polarization due to oxygen reduction and activation polarization due to hydrogen generation. At the Tafel experiments result, the corrosion density in welded with ER5183 welding material presented the lowest value.

• 로봇학회논문지
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• 제11권4호
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• pp.217-225
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• 2016

Dynamic Positioning (DP) is used to automatically maintain the position and heading of a floating structure subjected to environmental disturbances. A DP control system is composed of a motion controller to compute the desired force and moment and a thrust allocator to distribute the computed force and moment to multiple thrusters considering mechanical and operational constraints. Among various thruster configurations, azimuth thrusters or propeller/rudder pairs tend to make the allocation problem difficult to solve, because these types of propulsion systems include nonlinear constraints. In this paper, a dynamic positioning strategy for a twin-thruster ship that is propelled by two azimuthing thrusters is addressed, and a thrust allocation method which does not require a numerical optimization solver is proposed. The applicability of the proposed method is demonstrated with an experiment using an autonomous boat.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권1호
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• pp.65-71
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• 2011

Seakeeping analysis has progressed from the linear frequency-domain 2D strip method to the nonlinear timedomain 3D panel method. Nevertheless, the violent free surface flows such as slamming and green water on deck are beyond the scope of traditional panel methods based on potential theory. Recently, Computational Fluid Dynamics (CFD) has become an attractive numerical tool that can effectively deal with the violent free surface flows. ABS, as a classification society, is putting forth a significant amount of effort to implement the CFD technology to the advanced strength assessment of modern commercial ships and high-speed naval craft. The main objective of this study is to validate the CFD technology as a seakeeping tool for ship design considering fully nonlinear three-dimensional slamming and green water on deck. The structural loads on a large container carrier were successfully calculated from the CFD analysis and validated with segmented model test measurements.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.351-358
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• 2001

In this study, for the investigation of effects of several parameters, such as fluid mesh boundary size, cylinder or block shape, dimensions of depth, breadth and length at free suface, and fluid mesh element size to the depth direction on a reliable shock response of finite element model under underwater explosion with consideration of the bulk cavitation analysis of a simplified surface ship was carried out using the LS-DYNA3D/USA code. The shock responses were not much affected by the fluid mesh parameters. The computational time was greatly dependent on the number of DAA boundary segments. It is desirable to reduce the DAA boundary segments in the fluid mesh model, and it is not necessary to cover the fluid mesh boundary to or beyond the bulk cavitation zone just for the concerns about an initial shock wave response. It is also the better way to prefer cylinder type of the fluid mesh model to the block one.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1995년도 VTS and IBS 95 The Korean Institute of Navigation 1995년도
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• pp.184-192
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• 1995

Although ship's draught information onboard is substantial for both the safety of navigation and the estimation of loaded cargoes its accuracy depends in traditional surveying method on the skillfulness of observers and the condition of the sea surface round the vessel. To obtain more accurate information accessibly measuring instruments with sophisticated sensors such as mechanical electronic and ultrasonic transducers have been developed. however they have still limitation in accuracy and in making up a system due to the complexity of processing signal. In this paper we propose a he technique for analyzing ultrasonic pulse signal in order to improve the measurement accuracy and simplify a remote sensing system of draught by ultrasonic waves. This technique is useful for measuring draught being considered the influence of sea surface fluctuation and for transferring its data briefly to required equipment in integrated bridge system.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.540-558
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• 2015

Maneuvering oblique towing test is simulated in a Computational Fluid Dynamic (CFD) environment to obtain the linear and nonlinear velocity dependent damping coefficients for a DTMB 5512 model ship. The simulations are carried out in freely accessible OpenFOAM library with three different solvers, rasInterFoam, LTSInterFoam and interDyMFoam, and two turbulence models, $k-{\varepsilon}$ and SST $k-{\omega}$ in presence of free surface. Turning and zig-zag maneuvers are simulated for the DTMB 5512 model ship using the calculated damping coefficients with CFD. The comparison of simulated results with the available experimental shows a very good agreement among them.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.325-342
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• 2020

The current study is focused on the evaluation of the ultimate strength of stiffened panels found in ship hull structures that are subjected to combined uniaxial thrust, in-plane and out-of-plane bending moments. This loading condition, which is in general ignored when performing buckling checks, applies to representative control geometries (stiffener with attached plating) as a consequence of the linearly varying normal stresses along the ship's depth induced by the hull-girder vertical bending moment. The problem is generalized by introducing a non-uniform thrust described by a displacement ratio and rotation angle and by introducing the slenderness ratios, within the practical range of interest. The formed design space is explored through methods sourcing from Design of Experiments and by applying non-linear finite element procedures. Surrogate empirical models have been constructed through regression analysis and Response Surface Methods. An additional empirical model is provided to the literature for predicting the ultimate strength under uniaxial thrust. The numerical experimentation has shown that is a significant influence on the ultimate strength of stiffened panels as the thrust non-uniformity increases.