• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.717-726
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• 2016

This study evaluated the effect of aspect ratio of an enclosure with a heated inner circular cylinder on three-dimensional natural convection. The immersed boundary method was used to model the inner circular cylinder based on the finite volume method. The Rayleigh number was varied between $10^5$ and $10^6$, and the Prandtl number was maintained at 0.7. The aspect ratio of the three-dimensional enclosure was changed in steps of 1 within a range of 1-4 by increasing the width of the enclosure. In this study, the flow and thermal fields in the enclosure reached the steady state, and showed a mirror-symmetric pattern with respect to the center plane (x=0). In addition, the surface-averaged Nusselt number of the inner circular cylinder increased, while the total surface-averaged Nusselt number of the enclosure walls decreased with increase in the aspect ratio of the enclosure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.1
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• pp.71-83
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• 2004

The purpose of this study is to present an analysis method for the prediction of the changes m ground conditions. To this end, three dimensional convergence displacements are analyzed in several ways to estimate the trend of displacement changes. Three-dimensional arching effect is occurred around the unsupported excavation surface including tunnel face when a tunnel is excavated in a stable rock mass. If the ground condition ahead of tunnel face changes or a weak zone exists, a diagnostic trend of displacement change is observed by the 3 dimensional measurement and numerical analysis. Therefore, the change of ground condition and the existence of a weak zone ahead of tunnel face can be predicted by monitoring 3-dimensional absolute displacements during excavation, and applying the methodology (the ratio of L/C, $C/C_o$, etc.) presented in this study.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.1-8
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• 2001

The flow field inside a cylinder of four-valve Sl engine was investigated quantitatively using a three-dimensional Laser Doppler Velocimetry system, to determine how stroke changes affect the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, the sane intake manifold, engine head, cylinder, and the piston were used to examine the flow characteristics in different strokes. Quantification of the flow field was done by calculating three major parameters which are believed to adequately characterize in cylinder motion. These quantities were TKE, tumble and swirl ratios. The LDV results reveal that flow patterns are similar, the flow velocities scale with piston speed but another parameters such as TKE, and tumble and swirl numbers are not the same for different stroke systems.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.233-234
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• 2003

Fly ash enters axial compressor when a turbomachinery is operated in an adverse environment. We have numerically investigated erosion of the blade and shroud in the turbulent compressor passage flow under the influence of gas-particle two-phase interaction. There have appeared quasi-three dimensional calculations on this subject but not the complete three-dimensional gas-particle interaction as done in the present work. Lagrangian particle tracing technique is used on the base of parallel processing for efficient calculation. Accuracy of the present code is tested using the benchmark lPL nozzle. In the DFVLR compressor blades, we have shown that a large number of particles passing through the tip clearance make impact on the blade tip and on the shroud. Higher degree of erosion is resulted by the heavier particles due to the centrifugal force.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.203-204
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• 2003

Fly ash enters axial compressor when a turbomachinery is operated in an adverse environment. We have numerically investigated erosion of the blade and shroud in the turbulent compressor passage flow under the influence of gas-particle two-phase interaction. There have appeared quasi-three dimensional calculations on this subject but not the complete three-dimensional gas-particle interaction as done in the present work. Lagrangian particle tracing technique is used on the base of parallel processing for efficient calculation. Accuracy of the present code is tested using the benchmark JPL nozzle. In the DFVLR compressor blades, we have shown that a large number of particles passing through the tip clearance make impact on the blade tip and on the shroud. Higher degree of erosion is resulted by the heavier particles due to the centrifugal force.

• Journal of the Korean Society of Visualization
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• v.13 no.1
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• pp.21-25
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• 2015

Three-dimensional vortex structures in the corner region of translating normal plates are visualized experimentally with defocusing digital particle image velocimetry. Vortex formation processes for three plates with corner angle $60^{\circ}$, $90^{\circ}$, and $120^{\circ}$ are compared in order to study the effect of corner shape on vortex formation. In all cases, the self-induction of the starting vortex and its interaction with the potential flow induced by the moving plate cause the vortex to change its form dynamically after the plate starts to translate. While the vortex near a corner follows the plate in the low corner angle of $60^{\circ}$, the vortex separates early from the plate and its forward motion becomes slow in the high corner angle of $120^{\circ}$. It is also found that the starting vortex can transport inward at the corner, which depends on the corner angle.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.34-38
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• 2008

Commercially available magnetic barrel machines equipped with permanent magnets have certain limitations: work can only be finished effectively in limited areas of the container because permanent magnets are arranged two-dimensionally on the magnet disk. We overcame this problem by developing a new magnetic barrel machine equipped with a three-dimensional magnet arrangement. The effectiveness of the new machine has already been reported; this study improved the machine's polishing ability by changing the polarity of magnets on a magnet block. Polishing experiments confirmed the most effective arrangement of magnets on the magnet block. An alternating arrangement of north and south poles produced far superior polishing characteristics than a uniform arrangement of the same pole facing outward. Alternating polarity probably causes increased quantities of barrel media to work together. Finally, we introduced stronger permanent magnets to the magnet block, and found that the increased magnetic field also improved polishing ability.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.269-272
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• 2005

For the three decades, the mold-filling of injection molding process was modeled as Hele-Shaw model. However, this model can not consider the 3D effect. In this paper, numerical simulations of three dimensional mold-filling during the filling phase were performed. The governing equations were discretized by segregated finite element method, which used equal order interpolation for pressure and velocity fields. The iterative linear equation solver (JCG, SOR) was employed for the solution of the momentum and pressure equations. Volume of Fluid (VOF) was employed for the melt front advancement. To check the validity of the numerical results, the results were compared with the experimental ones. The agreements between the experiment and the numerical results were found to be satisfactory.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.383-386
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• 2003

This paper deals with transmission loss of 3-dimensional rectangular plenum lined chamber. There are three kinds of rectangular plenum lined chamber: throughflow type, flow-reversal type, and end-in/side-out type. The combination of above three types of rectangular plenum lined chamber is used for the commercial HVAC system and automobile exhaust system. However, the ambiguity and complexity of sound absorbing material property and 3-dimensional property have impeded research. In this paper, the transmission loss of three kinds of rectangular plenum lined chamber is derived and calculated. The effect of increase of sound absorbing material is also considered. Analytical solution is calculated by using the locally-reacting property of sound absorbing material.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.8
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• pp.635-642
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• 2009

The three-dimensional turbulent wingtip vortex flows have been examined in the present study by using the commercial code FLUENT. The standard ${\kappa}-{\varepsilon}$ model is used as a closure relationship. The wing is constructed by using an elliptic body whose aspect ratio is 3.8 and the NACA 16-020 airfoil section. The simulations for various angle attack (${\alpha}=0^{\circ}$, $5^{\circ}$, and $10^{\circ}$) are carried out. The effect of Reynolds number is also investigated in this study. As the angle attack increases, the wingtip vortex becomes stronger. However, the relative vortex strength to inlet velocity decreases as Reynolds number increases.