• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.116-120
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• 2009

A two-dimensional unsteady inviscid flow solver has been developed for the simulation of complex geometric configurations on adaptive Cartesian meshes. Embedded condition was used for boundary condition and a predictor-corrector explicit time marching scheme was used for time-accurate numerical simulation. The Cartesian mesh generator, which was previously developed for steady problem, was used grid generation for unsteady flow. The solver was based on ALE formulation for body motion. For diminishing the effects of cut-cells, the cell merging method was used. Using cell merging method, it was eliminated the CFL constraints. The conservation problem, which is caused cell-type variation around region swept by solid boundary, was also solved using cell merging method. The results are presented for 2D circular cylinder and missile launching problem.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.124-131
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• 2015

The good performance of a vortex shedder is defined by strong and stable vortex generated under the condition of most linearity in Strouhal number and low power loss. In this paper, the flow past a bluff body of circular cylinder with a slit normal to the flow has been analyzed focusing on drag coefficient, linearity of Strouhal number and flow resistance (K-factor). The ANSYS/FLUENT package is used for flow simulation and the integration method of computational code to iSIGHT platform is employed for automated design cycle. This study results the design with (0.20~0.267) blockage ratio and 0.10 slit ratio as the best shedder for vortex flowmeter and this results are in well agreement with the experiment. As the combination of GAMBIT, FLUENT, and iSIGHT substitutes the design parameters automatically according to the input data, this method designs effectively the vortex shedder with less design cycle time and low manufacturing cost eliminating the human intervention bottleneck.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.3
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• pp.26-31
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• 1991

The scattering property of TMz illuminated a elliptic dielectric cylinders with arbitrary cross section are analyzed by the boundary element techniques. The boundary element equations are for- mulated via Maxwell's equations, weighted residual of Green's theorem, and the boundary conditions. The unknown surface fields on the boundaries are then calculated by the boundary element integral equations. Once the surface fields are found, the scattered fields in far-zone and scattering widths (SW) are readily determined. To show the validity and usefulness of this formulation, computations are compared with those obtained using analytical method and one layer circular cylinder. As exten- sion to arbitrary cross-sectioned cylinders, plane wave scattering from a elliptic dielectric cylinders are numerically analyzed. A general computer program has been developed using the quadratic ele- ments(Higher order borndary elements) and the Gaussian quadrature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.518-525
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• 2000

This paper presents a new wavelet-based structural diagnostic technique. A continuous Gabor wavelet transform is shown to a very effective method in detecting damage in a beam. The beam is excited by a broad-band excitation force. For satisfactory results, the selection of an optimal wavelet is very important though the wavelet transform outperforms existing techniques such as the Wigner-Ville distribution. A specific example is given in a solid circular cylinder with a small defect.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.50-60
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• 2016

Laminate composites have a number of excellent characteristics in aspects of strength, stiffness, bending, and buckling. Buckling and postbuckling analysis of laminate composites with layups of [90/0]2s, $[{\pm}45/90/0]s$, $[{\pm}45]2s$ has been carried using the Total Lagrangian nonlinear Newton-Raphson method. The formulation of a geometrically nonlinear composite shell element based on a nonlinear large deformation method is presented. The used element is an eight-node degenerated shell element with six degrees of freedom. Square, circular cylinder, and arch panel laminate geometries were analyzed to verify the effects of the layups on the buckling and postbuckling behavior. The results showed that the effects of laminate layups on bucking and postbuckling behavior and the present formulation showed very good agreement with existing references.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.304-309
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• 1997

A method to mitigate the thermal stratification flow of a horizontal pipe line is proposed by heating external bottom of the pipe with electrical heat tracing. Unsteady two dimensional model has been used to numerically investigate an effect of the external Denting to the thermally stratified flow. The dimensionless governing equations are solved by using the control volume formulation and SIMPLE algorithm. Temperature distribution, streamline profile and Nusselt numbers of fluids and pipe walls with time are analyzed in case of externally heating condition. no numerical result of this study shows that the maximum dimensionless temperature difference between the hot and the cold sections of pipe inner wall is 0.424 at dimensionless time 1,500 ann the thermal stratification phenomena is disappeared at about dimensionless time 9,000. This result means that external heat tracing can mitigate the thermal stratification phenomena by lessening $\Delta$ $T_{ma}$ about 0.1 and shortening the dimensionless time about 132 in comparison with no external heat tracing.rnal heat tracing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.127-133
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• 2001

Photoelastic isochromatic fringes related to the difference of principal stresses have some bandwidth whose light intensities are not constant and unsymmetrical in experimental image. Hence it is difficult to measure fringe order accurately at a data point by visual observation. In this study, the method of fringe sharpening, which can extract sharpened lines from both full-and half-order fringes by digital image processing, is developed. To test the method, various simple photoelastic fringe patterns are simulated and their image are processed to yield sharpened lines. The method is than applied to general problem such as image of a circular disk compressed by concentrated loads and a cylinder subjected to internal pressure. The procedure is proved to be capable of extracting sharpened lines accurately from photoelastic isochromatic fringes.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.71-76
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• 2004

An extension of our recently developed locally linear reconstruction scheme to 2 dimensional incompressible flow solver is presented. The solver is based on a semi-implicit fractional step method in which the convective term is discretized by Adams-Bashforth method and the diffusion term by Crank-Nicolson method. Several numerical examples are tested to demonstrate the mesh type independent accuracy of the solver, which include decaying vortex flow, square cavity flow, and flow around a circular cylinder. The above examples are solved on quadrilateral or hybrid meshes. For all numerical examples, we obtained reasonable results.

• Nuclear Engineering and Technology
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• v.28 no.4
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• pp.405-414
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• 1996

In this paper, the unsteady 2-dimensional turbulent flow model for thermal stratification in a pressurizer surge line of PWR plant is proposed to numerically investigate the heat transfer and flow characteristics. The turbulence model is adapted to the low Reynolds number K-$\varepsilon$ model (Davidson model). The dimensionless governing equations are solved by using the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The results are compared with simulated experimental results of TEMR Test. The time-dependent temperature profiles in the fluid and pipe nil are shown with the thermal stratification occurring in the horizontal section of the pipe. The corresponding thermal stresses are also presented. The numerical result for thermal stratification by the outsurge during heatup operation of PWR shows that the maximum dimensionless temperature difference is about 0.83 between hot and cold sections of pipe well and the maximum thermal stress is calculated about 322MPa at the dimensionless time 28.5 under given conditions.

• Journal of Ocean Engineering and Technology
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• v.1 no.1
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• pp.65-72
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• 1987

두개의 동일한 원통이 두중심점을 잇는 선에 대하여 수직인 방향으로 저동할때 발생되는 정상류에 대한 해를 구하였다. 관련된 자변수들간의 어떤 가정하에서 본문제는 Stokes문제가 될 수 있었다. 유동함수를 급수전개하였으며, 급수의 계수수함수는 penta-diagonal matrix를 풀어 구할 수 있었다. 해의 결과에 의하면 원통 주위에 몇개의 소용돌이가 생겼며 그소용돌이의 수는 두 원통간의 거리에 따라 달라 졌다. 두 원통간의 거리가 커짐에 따른 점근적 성질을 단일 원통의 경우와 비교하여 확인하였다.