• 한국정밀공학회지
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• 제9권1호
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• pp.44-52
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• 1992

A post-processor is developed to be effectively usable in the personal computer. 3-dimensional controur lines are shown on the surface of the finite element model and also on the 3-dimensional cutting plane, using the function linearly interpolated onto the triangular elements which are constructed on the surface or sectional polygons. And these polygons are originated from the finite element model, 3-dimensional model is projected on the plane with hidden line removal by comparision technique[6]. The graphic data file is used to increase the protability of the program. It is easy to use in the other computer system if the graphic routine adopted that computer system is developed. The developed program has wide applications in 3-dimensional finite element analysis.

• 대한기계학회논문집B
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• 제27권3호
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• pp.374-380
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• 2003

This paper proposes dimensionless correlations predicting properties of the frost layer formed on a cold flat surface. Experiments are carried out to obtain the correlations with various environmental parameters such as air temperature, air velocity, absolute humidity, and cooling plate temperature. As a result, the frost properties (frost layer thickness, density, surface temperature, thermal conductivity) are correlated as a function of Reynolds number, Fourier number, absolute humidity and non-dimensional temperature by using a dimensional analysis. The correlations agree well with the previous and our experimental data within a maximum error of 10%, and are used to predict the frost properties in the following ranges: Reynolds number of 20216 to 53763, Fourier number of 0.1962 to 2.5128, absolute humidity of 3.22 to 8.47, and non-dimensional temperature of 0.125 to 0.5.

• 한국생산제조학회지
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• 제23권2호
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• pp.118-126
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• 2014

In this paper, a new method is proposed for the five-degree-of-freedom precision alignment and stitching of three-dimensional surface-profile data sets. The control parameters for correcting thealignment error are calculated from the surface profile data for overlapped areas among the adjacent measuring areas by using the "least squares method" and "maximum lag position of cross correlation function." To ensure the alignment and stitching reliability, the relationships betweenthe alignment uncertainty, overlapped area, and signal-to-noise level of the measured profile data are investigated. Based on the results of this uncertainty analysis, an appropriate size is proposed for the overlapped area according to the specimen's surface texture and noise level.

• 전자공학회논문지A
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• 제29A권7호
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• pp.64-72
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• 1992

VLSI 전송선로의 커패시턴스를 3차원으로 계산하였다. Green's function과 표면전하밀도의 곱의 형태로 주어지는 적분식을 풀어서 커패시턴스를 구하였다. 이때, 표면전하밀도는 도체의 표면을 균일한 면적을 갖는 미소 면적소로 나누어 주었을 때 각각의 면적소 내에서는 일정한 상수값을 갖는다고 가정하였다. 지금까지의 Green's function을 이용한 적분방법에서는 적분식의 계산을 Fourier 적분의 형태로 변환하여 계산하였기 때문에 계산과정에서 어느정도의 오차가 있을 수 밖에 없었지만, 본 논문에서는 Fourier 적분을 사용하는 대신에 이중 적분을 직접적으로 적분할 수 있는 방법을 제시하였다. 이 방법을 사용하여 적용한 결과를 기존의 결과들과 비교를 함으로써, 이의 정확성을 입증하였다.

• 대한조선학회논문집
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• 제45권3호
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• pp.258-268
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• 2008

The radiation potential of a ship advancing in waves is studied using the 3D time-domain forward-speed free-surface Green function and the Green integral equation. Numerical solutions are obtained by making use of the 2nd order BEM(Boundary Element Method) which make it possible to take account of the line integral along the waterline in a rigorous manner. The 6 degree of freedom motion memory functions of a hemisphere and the Wigley seakeeping model obtained by direct integration of the time-domain 3D potentials over the wetted surface are presented for various Froude numbers.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2401-2405
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• 2008

In the present study, a three-dimensional least square/level set based two-phase flow code was developed for the simulation of three-dimensional sloshing problems using finite element discretization. The present method can be utilized for the analysis of a free surface flow problem in a complex geometry due to the feature of FEM. Since the finite element method is employed for the spatial discretization of governing equations, an unstructured mesh can be naturally adopted for the level set simulation of a free surface flow without an additional load for the code development except that solution methods of the hyperbolic type redistancing and advection equations of the level set function should be devised in order to give a bounded solution on the unstructured mesh. From the numerical experiments of the present study, it is shown that the proposed method is both robust and accurate for the simulation of three-dimensional sloshing problems.

• 한국CDE학회논문집
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• 제1권1호
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• pp.65-75
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• 1996

This paper describes an automatic finite element(FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid and shell structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional solid and shell structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.409-413
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• 2005

Even though the relative importance of length scale of flow system allow us to simplify three dimensional flow problem to one or two dimensional representation, many systems still require three dimensional analysis. The objective of this study is to develop an efficient and accurate finite element model for analyzing and predicting three dimensional flow features in natural rivers and to offend to model spreading of pollutants and transport of sediments in the future. Firstly, three dimensional Reynolds averaged Navier-Stokes equations with the hydrostatic pressure assumption in generalized curvilinear coordinates were combined with the kinematic free-surface condition. Secondly. to simulate realistic high Reynolds number flow, the model employed the Streamline Upwind/Petrov-Galerkin(SU/PG) scheme as a weighting function for the finite element method in conjunction with an appropriate turbulence model(Smagorinsky scheme for the horizontal plain and Mellor-Yamada scheme for the vertical direction). Several tests is performed for the purpose of validation and verification of the developed model. A simple rectangular channel, 5-shaped and U-shaped channel are used for tests and comparisons are made with RMA-10 model. Runs for each case is converged stably without a oscillation and calculated water-surface deformation, longitudinal and transversal velocities, and velocity vector fields are in good agreement with the results of RMA-10 model.

• 항공우주시스템공학회지
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• 제7권3호
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• pp.1-6
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• 2013

Numerical optimization of two dimensional high lift configuration was performed with flow solver and optimization method based on RSM(Response Surface Model). Navier-Stokes solver with Spalart-Allmaras turbulence model was selected for the simulation of highly complex and separated flows on the flap. For the simultaneous optimization of both flap shape and setting (gap/overlap), 10 design variables (eight variables for flap shape variation and two variables for flap setting) were chosen. In order to generate the response surface model, 128 experimental points were selected for 10 design variables. The objective function considering maximum lift coefficient, lift to drag ratio and lift coefficient at specific angle of attack was selected to reduce flow separation on the flap surface. The present method was applied to two dimensional fowler flap in landing configuration. After applying the present method, it was shown that the optimized high lift configuration had less flow separation on the flap surface and lift to drag ratio was suppressed over entire angle of attack range.

• 한국통신학회논문지
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• 제21권2호
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• pp.301-312
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• 1996

A new approach is presented for recovering the 3-D shape from shading image. Photometric Stereo Method (PSM) is generally based on the direct illumination. In this paper, the reflectance function is derived by introduceing the indirect diffuse illumination in PSM and then applied to hybrid reflectance model which consists fo two components; the Lambertian reflectance and the speclar reflectance. Under the hybrid reflectance model and the indirect diffuse illumination circumstances, the 3-D shape of object can be recovered from the suface normal vector extracted from the surface roughness, the surface reflectance ratio, and the intensity value of a pixel. This method is rapid because of using the reference table and simplifies the restriction condition about the reflectance function existing in prior studies. The recovery efficiency in our method is better than that in prior studies. Also, this method is applied to various types of surfaces by defining general reflectance function.