• Journal of the Korean Institute of Navigation
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• v.17 no.1
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• pp.61-78
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• 1993

Large offshore structure are to be considered for oil storage facilities , marine terminals, power plants, offshore airports, industrial complexes and recreational facilities. Some of them have already been constructed. Some of the envisioned structures will be of the artificial-island type, in which the bulk of structures may act as significant barriers to normal waves and the prediction of the wave intensity will be of importance for design of structure. The present study deals wave scattering problem combining reflection and diffraction of waves due to the shape of the impermeable rigid upright structure, subject to the excitation of a plane simple harmonic wave coming from infinity. In this study, a finite difference technique for the numerical solution is applied to the boundary integral equation obtained for wave potential. The numerical solution is verified with the analytic solution. The model is applied to various structures, such as the detached breakwater (3L${\times}$0.1L), bird-type breakwater(318L${\times}$0.17L), cylinder-type and crescent -type structure (2.89L${\times}$0.6L, 0.8L${\times}$0.26L).The result are presented in wave height amplification factors and wave height diagram. Also, the amplification factors across the structure or 1 or 2 wavelengths away from the structure are compared with each given case. From the numerical simulation for the various boundary types of structure, we could figure out the transformation pattern of waves and predict the waves and predict the wave intensity in the vicinity of large artificial structures.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.3
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• pp.247-255
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• 2012

Numerical calculations are carried out for the natural convection in a square enclosure with two hot cylinders induced by temperature difference between a cold outer rectangular cylinder and two hot circular cylinders. A two-dimensional solution for unsteady natural convection is obtained, using the immersed boundary method (IBM) to model two inner circular cylinders based on finite volume method, for different Rayleigh numbers varying over the range of $10^3$ to $10^5$. The study goes further to investigate the effect of the location of two cylinders on the heat transfer and fluid flow. The location of inner circular cylinders is changed vertically along the center-line of square enclosure. The changes of heat transfer quantities have been presented.

• Computational Structural Engineering
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• v.11 no.1
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• pp.161-170
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• 1998

A general formulation of the long cylinder tolerance design for the joint structure is here presented. The aim of this paper is to calculate the tolerance of joint by defining tolerance as a kind of uncertainty and to obtain the robustness of the joint structure. It is formulated on the bases of the minimum sensitivity theorem. The objective function is the tolerance sensitivity for the Von-Mises stress. It also took into full account the stress, displacement and weight constraints. PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm is used to solve the constrained nonlinear optimization problem. The finite element analysis is performed with CST(Constant-Strain-Triangle) axisymmetric element. Sensitivities for design variables are calculated by the direct differentiation method. The numerical result is presented for the cylindrical structure where the joint tolerance is treated as random variables.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.610-616
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• 1990

The fracture mechanics analysis of surface cracks in plates and cylindrical geometries is important in the integrity evaluation of flawed structural components. The objective of this paper is, thus, to numerically investigate an interaction effect of two surface cracks in plate and cylindrical geometries. The effect of crack spacing on the magnitude of the stress intensity factor(K) is investigated using the line-spring model. For the case of a finite plate under uniaxial loading, the effect of crack spacing on the K values is negligible. However, for the case of a cylinder under moderate internal pressure, a significant increase in K values is observed at the deepest point of the surface crack.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.68-75
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• 2000

In this paper, we analyzed the radiation patterns of a monopole antenna mounted on cylinder and EM penetration problems in the complex structures by using FDTD method associated with 3-D PML absorbing boundary condition. In order to validate the proposed FDTD code, the radiation patterns of monopole antenna mounted on cylinders were compared with the exact Carter's solutions. As a results, the predicted radiation pattern exhibited excellent agreement with exact solution. And the FDTD code is applied to analyze the EM penetration problems in complex structures, Blackhawk helicopter. As the plane wave is excited, a significant amount of energy penetrates the helicopter structure, and it is dependent on aperture/airframe interface.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.89-91
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• 1999

The performance of circuit interruption of $SF_6$ puffer cylinder type gas circuit breaker(GCB) has been evaluated from the results of electrical insulation strength which is depend on material property, such as $SF_6$ gas density in circuit breaker tank. In order to determine circuit breaker dimension in the safety criteria. electrical field analysis has been done by finite element method. Gas density of concerned area in the circuit breaker has been calculated. In order to predict small current break performance, Electrical field analysis result must be calculated based the results of density from cold flow dynamics. The proposed method has been carried out and evaluated for 362kV class high voltage GIS.

• Steel and Composite Structures
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• v.1 no.4
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• pp.411-426
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• 2001

This paper treats the failure analysis of prestressing steel wires with different kinds of localised damage in the form of a surface defect (crack or notch) or as a mechanical action (transverse loads). From the microscopical point of view, the micromechanisms of fracture are shear dimples (associated with localised plasticity) in the case of the transverse loads and cleavage-like (related to a weakest-link fracture micromechanism) in the case of cracked wires. In the notched geometries the microscopic modes of fracture range from the ductile micro-void coalescence to the brittle cleavage, depending on the stress triaxiality in the vicinity of the notch tip. From the macroscopical point of view, fracture criteria are proposed as design criteria in damage tolerance analyses. The transverse load situation is solved by using an upper bound theorem of limit analysis in plasticity. The case of the cracked wire may be treated using fracture criteria in the framework of linear elastic fracture mechanics on the basis of a previous finite element computation of the stress intensity factor in the cracked cylinder. Notched geometries require the use of elastic-plastic fracture mechanics and numerical analysis of the stress-strain state at the failure situation. A fracture criterion is formulated on the basis of the critical value of the effective or equivalent stress in the Von Mises sense.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.35-41
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• 2010

An overload limiter is used to prevent its overturning accident during an operation of a movable crane. Recently the indirect measuring method, which measures hoisting load and overturning moment of overload limiter, demands instead of the existing method, which measures only hoisting load. The indirectly measuring method is how to conduct the hoisting load and overturning moment as measuring the load of hydraulic cylinder for a luffing driving of boom. So we need to develop the multi-angular pin type load cell with the measuring angle of ${\pm}10$ degree instead of the existing load cell with the measuring angle of ${\pm}2$ degree. In this study the finite element analysis is conducted to evaluate the effect of the aspect ratio of measuring cross section on the measuring limit of the load cell to develop the many-angular pin type load cell. For this investigation, the aspect ratio of measuring cross section and load applying angle were adopted as design parameters and the stresses of measuring part were evaluated for each parameter.

• Bulletin of the Society of Naval Architects of Korea
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• v.11 no.2
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• pp.1-6
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• 1974

The three-dimensional correction factor of the added mass of finite-length elliptic cylinders in vertical vibration in a free surface was calculated. This problem has already been dealt by T. Kumai[5] to contribute to analytical prediction of the three-dimensional correction factor for the added mass in vertical vibration of ships. In Kumai's work, the body boundary condition involved in the appropriate boundary value problem was approximately treated in the course of obtaining the solution. In this work, obtaining the solution derived from mathematically exact treatment of the body boundary condition, the author recalculated the three-dimensional correction factor for length-beam ratio $4{\sim}8$, beam-draught ratio $2.00{\sim}4.50$ and number of nodes from 2 to 7. And the numerical results were compared with both Kumai's results and the author's experimental data for two and three-noded vibrations of the cylinder of beam-draught ratio 2.40 The comparison of the numerical results shows that the author's are always higher than the Kumai's as expected. And the comparison of the numerical results with experimental data shows that the Kumai's numerical results have less deviation in case of two-noded vibration, and that, in case of three-noded vibration, the author's numerical results are in fairly good correspondence.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.395-408
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• 1987

Turbulent flows in an axisymmetric reciprocating engine are numerically simulated at it's suction and compression stage. Amounts of heat transfer through the wall of the cylinder are also estimated. k-.epsilon. turbulence model is adopted and the law of the wall is applied at grid-points near the wall. More than 40 * 40 grids are reguried to reasonably predict flows and the 3-level finite difference scheme for the time derivative term appears to be effective rather than the 2-level scheme. Calculated mean velocity distributions shows good agreements with an available experimental data. The program reasonably simulates flow patterns and pressures throughout the suction and the compression stages of the reciprocating engine. Predicted intensities of turbulence are still deviated from measured data. Further researches for turbulence modeling are expected.