• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.3
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• pp.19-25
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• 1988

The three-dimensional boundary value problem for the unsteady motion of a ship which is translating and oscillating on the free surface of a deep water formulated. Under the assumption that the forward speed is small and order of $\varepsilon$, all formulations are made up to the first order of $\varepsilon$. For the numerical calculation, the three-dimensional source distribution method is applied, and the triangular elements are used to represent the hull surface. The results for the added mass and the damping coefficient for Series 60, $C_B=0.7$ at Fn=0 and Fn=0.2 shows good agreements with those of Inglis, Chang, and Inglis and Price.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.1
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• pp.93-103
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• 1992

The hydrodynamic interaction characteristics between multiple floating bodies of semisubmersible type are examined for presenting the basic data for the design of huge offshore structures supported by a large number of the floating bodies in waves. The numerical approach is based on combination of a three-dimensional source distribution method and interaction theory which is exact within the context of linear potential theory. The method is applicable to an arbitrary number of three-dimensional bodies having any individual body geometries and geometrical arrangement with the restriction that the circumscribed, bottom-mounted, imaginary vertical cylinder for each body does not contain any part of the other body. The validity of this procedure was verified by comparing with numerical results obtained in the literature.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.124-130
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• 1994

This paper compared with the hydrodynamic interference acting on the semi-submersible element model with 1-lowerhull and 2-columns. In this case, calculation are applying the strip method and 3-dimensional source distribution method. As the wave frequency and the distance between increase, the influence effects of parts upon each other decrease and approach the results calculated by using the strip method. Thus, it can be prepared for the investigation of new practical method of investigation of new practical method of hydrodynamic forces acting on huge structures.

• Economic and Environmental Geology
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• v.19 no.4
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• pp.283-292
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• 1986

Finite element method with linear triangular and bilinear rectangular elements is applied to solve the three-dimensional potential distribution due to a point source of current located in or on the surface of the earth containing arbitrary two-dimensional resistivity distribution. The modeling technique developed in this paper is flexible to model conductive inhomogeneity and surface topographies, and more accurate to evaluate surface potentials than the conventional techniques using finite difference method. Since it is possible to reduce nodal points with acceptable accuracy, this modeling technique is very efficient and economic in terms of execution time and core space. A few geologic structures adequate to demonstrate above features are simulated in this paper.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.166-174
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• 1998

The distribution of oil film thickness in piston were measured by induced fluorescence method. A Xe lamp was used as light source. Coumarine-6 was mixed with oil as the fluorescent dye. Fluorescent signal which is proportional to the oil film thickness was acquired by CCD camera and transmitted to the personal computer as video signal. In order to solve the problem of measurement system, irregular distribution and unstability of light intensity, as well as to know the relationship between the oil film thickness and output signal, three different calibration techniques were used. Motoring and firing tests were performed in a single cylinder research engine with transparent liner. By analyzing the oil film thickness converted from the photographed image, it was observed that each of three piston rings scrapes the oil both upward and downward and oil film thickness is not uniform horizontally at a given piston land. The amount of oil in each land was considerably affected by the engine load. It is thought that the blow-by gas blows the oil down to the crankcase.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.101-107
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• 2006

Recently, with the increase in requirements for marine development, a marine urbanism is being visualized, with more and more huge-scale structures at the scope of the ocean space utilization. In particular, a pontoon-type structure has attracted attention, since The Floating Structures Association of Japan proposed a new concept as the most suitable one of floating airports. The Very Lage Floating Structure (VLFS) is considered a flexible structure, for a quite large length-to-breadth ratio and its geometrical flexibility. The main objective of this study is to makean exact and convenient prediction about the hydro-elastic response on very large offshore structures in waves. The numerical approach for the hydro-elastic responses is based on the combination of the three dimensional source distribution method and the dynamic response analysis method, which assumed a dividing pontoon type structure, as many rigid bodies connected elastic beam elements. The established hydo-elastic theory was applied to the radiation forces caused by motions of a whole structure, formulated using the global coordinate system, which has the origin at the center of the structure. However, in this paper, we took radiation forces, occurred by individual motions of floating bodies, into consideration. The calculated results show good agreement with the experimental and calculated results by Yago.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.46-55
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• 2004

Thermal characteristics of the various cooling methods in electronic equipment are studied numerically. A common chip cooling system is modeled as a parallel channel with protruding heat sources. A two-dimensional model has been developed for the numerical analysis of compressible. viscous. laminar flow. and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve this problem. The assembly consists of two channels formed by two covers and one printed circuit board that is assumed to have three uniform heat source blocks. Various cooling methods are considered to find out the efficient cooling method in a given geometry and heat sources. The velocity and the temperature fields. the local temperature distribution along the surface of blocks. and the maximum temperature in each block are obtained. The results are compared to examine the thermal characteristics of the different cooling methods both quantitatively and qualitatively.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.16-21
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• 2003

The very large container ships have been built recently and those ships have very small structural rigidity compared with the other conventional ships. As a result, the destruction of ship hull is occurred by the springing including to warping phenomena due to encounter waves. In this study, the solutions of hydrodynamic coefficients are obtained by solving the three dimensional source distribution method and the forward speed Green function representing a translating and pulsating source potential for infinite water depth is used to calculating the integral equation. The vessel is longitudinally divided into various sections and the added mass, wave damping and wave exciting forces of each section is calculated by integrating the dynamic pressures over the mean wetted section surface. The equations for six degree freedom of motions is obtained for each section in the frequency domain and stiffness matrix is calculated by Euler beam theory. The computations are carried out for very large ship and effects of bending and torsional ridigity on the wave frequency and angle are investigated.

• Journal of Ocean Engineering and Technology
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• v.10 no.1
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• pp.25-35
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• 1996

A numerical procedure is described for predicting the motion and structural responses of tension leg platforms(TLPs) in waves. The developed numerical approach is based on a combination of a three dimensional source distribution method and the dynamic response analysis method, in which the superstructure of TLPs is assumed to be flexible instead of rigid. Restoring forces by hydrostatic pressure on the submerged surface of a TLP have been accurately calculated by excluding the assumption of the slender body theory. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in the motion and structural analysis. The equations of motion of a whole structure are formulated using element-fixed coordinate systems which have the orgin at the nodes of the each hull element and move parallel to a space-fixed coordinate system. Numerical results are compared with the experimental and numerical ones, which are obtained in the literature, concerning the motion and structural responses of a TLP in waves. The results of comparison confirmed the validity of the proposed approach.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.923-930
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• 2002

Cooling characteristics of a parallel channel with protruding heat sources using convection and conduction heat transfer are studied numerically. A two-dimensional model has been developed for numerical prediction of transient, compressible, viscous, laminar flow, and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve the problem. The assembly consists of two channels formed by two covers and one printed circuit board which has three uniform heat source blocks. Six different cooling methods are considered to find out the most efficient cooling method in a given geometry and heat sources. The velocity and temperature fields of cooling medium, the temperature distribution along the block surface, and the maximum temperature in each block are obtained. The results are compared to examine the cooling characteristics of the different cooling methods.