• Proceedings of the Korea Water Resources Association Conference
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• 1987.07a
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• pp.113-122
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• 1987

A numerical simulation technique of three-dimensional finite difference model is developed to study the groundwater flow system in Dcjima, an upland area which faces Kasumigaura Lake. For general perspectives of the groundwater flow system, a steady state three-dimentional model is simulated. For the sedimentary mud formations which are found in the representative formation, three situations of hydraulic conductivity are considered, representing an isotropic condition and situations where the horizontal permeability is equal to 10 times and 100times of the vertical one. The finite difference grid used in the simulation has 60x50x30=90,000 nodes. A converged solution with a tolerance of 0.001 meter of hydraulic head is set. Having determined the flow net by using a steady state three-dimensional model. the results for the three cases of hydraulic conductivity are compared with the results of tracer methods (Bae and Kayane 1987) With the aid of four representative vertical cross-sections, groundwater flow systems in the study area are assumed. Water balances for the three cases indicate very good agreement between total recharge and discharge in each case Analyses of groundwater flow system based on the tritium concentrations and water quality measurements (Bae and Kayane 1987) are confirmed by the numerical simulation and the results obtained by these two methods appeared to be in close agreement.

• Transactions on Electrical and Electronic Materials
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• v.5 no.6
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• pp.215-218
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• 2004

This paper presents a three-dimensional numerical simulation for thermal oxidation process. A new elasto-viscoplastic model for robust numerical oxidation simulation is proposed. The three-dimensional effects of oxidation process such as mask lifting effect and corner effects are analyzed. In nano-scale process, the oxidant diffusion is punched through to the other side of the mask. The mask is lifted so the thickness of oxide region is greatly enhanced. The compressive pressure during the oxidation is largest in the mask corner of the island structure. This is because the masked area near the corner is surrounded by an area larger than the others in the island structure. This stress induces the retardation of the oxide growth, especially at the masked corner in the island structure.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.9-19
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• 2001

In this paper we present the aspect of inertial oscillation typically observed in the spin-up of fluids at low Rossby numbers in a circular cylinder. Numerical computations for the quasi three-dimensional equation as well as one-dimensional equation are performed to estimate the predictability of the one-dimensional equation with Ekman pumping/suction models. It is assumed that the discrepancy between the two results may be attributed to the inertial oscillation The detailed analysis to the numerical results reveals that the axial plane is dominated by a comparatively strong oscillatory flows caused by the inertial oscillation. In view of the fact that the time-averaged flow field however agrees to the Taylor-Proudman theorem, it is recommended that further analysis is needed to obtain an improved one-dimensional model like the Reynolds-averaged Navier-Stokes equation for turbulent flows.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.235-243
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• 2010

Three-dimensional structural analysis system for nuclear containment building is presented in this paper. This system includes high-performance plate/shell elements as finite element library. It also adopts numerical modeling technique for unbonded tendon as well as bonded tendon in prestressed concrete structures. This system is constructed by connecting several in-house program to a commercial program DIANA, and then is capable of performing nonlinear analysis for ultimate pressure capacity of nuclear containment building. Finally, three-dimensional structural analysis of CANDU-type containment building is carried out in order to test the reliability of this system. These numerical results are compared with reference values, which obtained from axisymmetric structural analysis.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1073-1082
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• 2003

Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole. calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.

• Tunnel and Underground Space
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• v.14 no.4
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• pp.287-294
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• 2004

To predict the temperature distribution around a underground rock storage cavern, two- and three- dimensional numerical analysis using FLAC was conducted. The effects of groundwater and latent heat on thermal properties were considered in numerical calculation. The temperature estimated by FLAC are compared with the temperature measured for 5-year operation at Gonjiam storage cavern. Estimated and measured temperatures showed great discrepancy when thermal properties from laboratory tests were used and showed good agreement when the effects from 20% of volumetric water fraction and latent heat were considered. However, the discrepancy still increased with operation time due to the heat flow from ground surface. Three-dimensional numerical models were established to closely approximate the boundary condition of the test site, and numerical results better agreement when groundwater and latent heat effects were considered.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.5
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• pp.550-559
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• 2014

Hydraulic performance of the 1 inch ball valve have been analyzed based on the three-dimensional Reynolds-averaged Navier-Stokes analysis and an experiment. The experimental test rig of the 1 inch ball valve has been developed to investigate pressure drop for the 1 inch ball valve. The numerical model, which has reliability and effectiveness, has been constructed through the grid dependency test and validation with the results of the experiment. Shear stress transport turbulence model has been used to enhance an accuracy of the turbulence prediction in the pipeline and ball valve, respectively. Effects of the ball valve angle on the flow characteristics and friction performance have been evaluated.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.4
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• pp.331-345
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• 2001

The increase of carbon monoxide in the ambient air due to the emissions from point sources without control was estimated using three -dimensional numerical models. The target area was Ulsan where one of the largest industrial complexes was located. As a typical example using numerical models for air quality impact analysis of criteria pollutants that will determine whether the air quality standards would be exceeded or not, the following approaches were suggested. They include: (1) investigation of pre-existing atmospheric conditions, (2) identification of major factors causing high concentrations, (3) selection of episode days. (4) preparation of three-dimensional meteorological data, (5) confirmation of agreement between measured and predicted concentrations in the emission conditions of episode days, and (6) estimation of the impact due to changes of the emission conditions. In the present work, daily meteorological conditions for the specific period were classified into four clusters of distinctive features, and the episode days were selected individually from each cluster. Emphasis was placed on the selection of episodes representing meteorological conditions conducive to high concentrations especially for point sources that were sensitive to the wind direction variations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1335-1342
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• 2000

Three-dimensional flow analysis and numerical optimization methods are presented for the design of an axial-flow fan. Steady, incompressible, three-dimensional Reynolds-averaged Navier-Stokes equations are used as governing equations, and standard k- ${\varepsilon}$ turbulence model is chosen as a turbulence model. Governing equations are discretized using finite volume method. Steepest descent method, conjugate gradient method and BFGS method are compared to determine the searching directions. Golden section method and quadratic fit-sectioning method are tested for one dimensional search. Objective function is defined as a ratio of generation rate of the turbulent kinetic energy to pressure head. Two variables concerning sweep angle distribution are selected as the design variables. Performance of the final fan designed by the optimization was tested experimentally.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.6
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• pp.431-438
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• 2005

Bubble behaviors in a circular tube have been analyzed numerically and experimentally by a three-dimensional tomography method, Initially, a multiplicative algebraic reconstruction technique (MART) which showed better results for previous studies of numerical simulations has been performed to confirm the accuracy of the three-dimensional reconstruction for the two-phase flow using a computer-synthesized phantom, Then, bubble behaviors have been investigated experimentally by the three-dimensional MART method using real projected data captured simultaneously by a laser and three CCD cameras for three angles of view, Also, the transient reconstructions have been attempted to analyze the real-time oxygen-bubble movements in water by the interval of 1/30 second.