• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.14 no.1
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• pp.43-56
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• 2010

The representative numerical algorithms to solve the time dependent Navier-Stokes equations are projection type methods. Lots of projection schemes have been developed to find more accurate solutions. But most of projection methods [4, 11] suffer from inconsistency and requesting unknown datum. E and Liu in [5] constructed the gauge method which splits the velocity $u=a+{\nabla}{\phi}$ to make consistent and to replace requesting of the unknown values to known datum of non-physical variables a and ${\phi}$. The errors are evaluated in [9]. But gauge method is not still obvious to find out suitable combination of discrete finite element spaces and to compute boundary derivative of the gauge variable ${\phi}$. In this paper, we define 4 gauge algorithms via combining both 2 decomposition operators and 2 boundary conditions. And we derive variational derivative on boundary and analyze numerical results of 4 gauge algorithms in various discrete spaces combinations to search right discrete space relation.

• Nuclear Engineering and Technology
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• v.31 no.2
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• pp.214-225
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• 1999

An accurate method is presented for flexural vibrations of sectorial plates having simply supported-free and free-free radial edges, when the circular edge is either clamped or simply supported. The classical Ritz method is employed with two sets of admissible functions assumed for the transverse vibratory displacements. These sets consist of : (1) mathematically complete algebraic-trigonometric polynomials which gurantee convergence to exact frequencies as sufficient terms are retained, and (2) comer functions which account for the bending moment singularities at re-entrant comer of the radial edges having arbitrary edge conditions. Accurate (at least four significant figures) frequencies and normalized contours of the transverse vibratory displacement are presented for the spectra of corner angles [90$^{\circ}$, 180$^{\circ}$(semi-circular), 270$^{\circ}$, 300$^{\circ}$, 330$^{\circ}$, 350$^{\circ}$, 355$^{\circ}$, 360$^{\circ}$ (complete circular)] causing a re-entrant comer of the radial edges. Future solutions drawn from alternative numerical procedures and finite element techniques may be compared with these accurate results.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.119-121
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• 2003

In the machine tool industry, direct drive linear motor technology is of increasing interest as a means to achieve high acceleration, and to increase reliability [1]. In this paper, we analyze and compare the characteristics of tubular motor with halbach and vertical magnet array respectively. We derive magnetic field solutions due to the PMs and to the currents. Motor thrust is then derived. The results are shown in good conformity with those obtained from the commonly used finite element method.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.957-964
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• 2011

New time schemes based on the FEM were developed and their performances were tested with 2D wave equation. The least-squares and weighted residual methods are used to construct new time schemes based on traditional residual minimization method. To overcome some drawbacks that time schemes based on the least-squares and weighted residual methods have, ad-hoc method is considered to minimize residuals multiplied by others residuals as a new approach. And variational method is used to get necessary conditions of ad-hoc minimization. A-stability was chosen to check the stability of newly developed time schemes. Specific values of new time schemes are presented along with their numerical solutions which were compared with analytic solution.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.27-32
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• 2000

In this study, the three-dimensional blood flow within the sac of KTAH(Korean artificial heart) is simulated using fluid-structure interaction model. The numerical method employed in this study is the finite element commercial package ADINA. The thrombus formation is one of the most critical problems in KTAH. High fluid shear stress or stagnated flow are believed to be the main causes of these disastrous phenomenon. We solved the fluid-structure interaction between the 3D blood flow in the sac and the surrounding sac material. The sac material is assumed as linear elastic material and the blood as incompressible viscous fluid. Numerical solutions show that high shear stress region and stagnated flow are found near the upper part of the sac and near the comer of the outlet during diastole stage.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.712_713
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• 2009

This paper deals with the analysis on eddy current looses of high speed permanent magnet synchronous motor (PMSM) for turbo compressor according to voltage source driving. This paper presents analytical procedures for calculation of the eddy current losses using Poynting theorem. On the basis of the magnetic vector potential and a two-dimensional (2-D) cylindrical coordinate system, this paper derived analytical solutions of the eddy current looses using phase current analysis. The eddy current losses of each harmonic obtained by fast Fourier transform (FFT) analysis of phase current are with results obtained from finite-element method (FEM).

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.5-7
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• 2007

This paper deals with design and analysis of thrust magnetic bearing for 300HP class high speed motor. Using the solutions obtained from equivalent magnetic circuits, we predicts the electromagnetic characteristics such as thrust, time constant and power loss according to design parameters. And then, using non-linear finite element analysis, a detailed design is performed considering saturation in order to meet requirements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1419-1426
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• 2000

A dynamic analysis of rectangular Reissner-Mindlin plate was carried out using pseudospectral method. The pseudospectral method is superior to the finite element method because of more rapid conver gence speed of approximate solutions. Especially, the improvement in accuracy of the pseudospectral method is remarkable. Numerical examples demonstrate the excellent performance and robustness of the pseudospectral method with respect to thickness ratio of rectangular Reissner-Mindlin plate. The natural frequencies of rectangular Reissner-Mindlin plate calculated with the pseudospectral method are more reliable than those calculated with other numerical methods.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1772-1777
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• 2007

This paper provides plastic limit loads of pipes with constant-depth, circumferential part-through surface cracks under combined pressure and bending. A key issue is to postulate discontinuous hoop stress distributions in the net-section. Validity of the proposed limit load solutions is checked against the results from three-dimensional (3-D) finite element (FE) limit analyses using elastic-perfectly plastic material behavior.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.183-188
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• 2007

In this paper, we propose a 2D-FE model in single impact with combined physical factors to obtain a unique residual stress by shot peening. Applied physical parameters include elastic-plastic deformation of shot ball, material damping coefficients, strain rate, dynamic friction coefficients. Single impact FE model consists of 2D axisymmetric elements. The FE model with combined factors showed converged and unique distributions of surface stress, maximum compressive residual stress and deformation depth. Further, in contrast to the FE models with rigid shot and elastic deformable shot, FE model with plastic deformable shot produces residual stresses very close to experimental solutions by X-ray diffraction. We therefore validated the 2D FE model with combined peeing factors and plastic deformable shot. This FE model will be a base of the 3D FE model for residual stresses by multi-impact shot peening.