• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1466-1471
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• 2004

In this paper, we report the numerical and experimental solutions of the axi-symmetric flows in the axial plane driven by an impingement of fluid from the bottom wall of a circular cylinder. We managed to visualize successfully the flow pattern shown on the vertical plane through the container axis. The numerical results are not show to compare well with the experimental results for the case of the Rossby number 3. Because the numerical results calculate on the assumption that vortex flows are axi-symmetric flow on the other hand real experimental results are show asymmetric flow. The numerical solutions reveal that inertial oscillation plays an important role at small Rossby numbers, or at a larger background rotation.

• Fibers and Polymers
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• 제5권3호
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• pp.209-212
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• 2004

A nonsteady axi-symmetric ideal flow solution is obtained here. It is based on the rigid perfect-plastic constitutive law with the Tresca yield condition and its associated flow rule. The process is to deform a circular solid disk into a spherical shell of prescribed geometry. It is assumed that there are no rigid zones and friction stresses. The solution obtained provides the distribution of kinematic variables and involves one undetermined function of the time. This function can be in general found by superimposing an optimality criterion.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1326-1334
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• 2000

The oscillatory excitation with a Strouhal number of 2.65 ncar the stagnation zone of hemispherical nose model was employed to control the laminar separation bubble and the transition to turbulence. The effects of oscillatory excitation upon the separation bubble and the transition were addressed in terms of kurtosis/skewness and time-frequency analyses. The measured noise spectrum of radiated sound from the turbulent boundary layer on the axi-symmetric infinite cylinder is compared with that by Sevik's wave-number white approximations. The noise sources in TBL on axi-symmetric cylinder and the caling of their far-field sound are also discussed.

• 대한기계학회논문집B
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• 제28권9호
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• pp.1133-1138
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• 2004

Shape optimization method was coupled with a conventional CFD analysis to find the optimal shape of ex-manifold diffuser which decreases the maldistribution of flow above the catalyst. Shape optimization results show that flow uniformity above the catalyst was increased about 28% fur the axi-symmetric case and about 18% for the asymmetric case. The axi-symmetric type can be applied to the diffuser of under floor catalyst and the asymmetric type can be applied to the diffuser of close coupled catalyst.

• 한국연소학회지
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• 제11권1호
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• pp.1-10
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• 2006

Oil-fired power plant usually uses several burners and combustion air is supplied to each burner through the complicated duct which is called windbox. A windbox should be designed to supply combustion air to each burner uniformly but, due to the complicated duct shape, flow distribution in the windbox is unbalanced and non-uniform supplies of combustion air are induced by these unbalanced flows in the windbox. These flow patterns tend to make flame unstable, increase the formation of pollutants and lower the overall combustion efficiency. To prevent these disadvantages, flow patterns in the windbox should be investigated for the uniform flow distribution. In this study, computational simulation method was used to investigate the flow distribution in a windbox and measured the velocities at the exit of burners in a real windbox and model tests to compare with CFD results. The results show two significant flow patterns. One is that the flow rates of each burner are different from each other and this means that all burners operate in different conditions of air to fuel ratio. The other is that the flow distribution at the exit of each burner is not axi-symmetric although the burner shape is axi-symmetric. Additionally some modifications of windbox shape and installation of baffles were proposed to make the uniform flow in the windox.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.137-144
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• 2006

Oil-fired power plants usually use several burners and the combustion air is supplied to each burner through the complicated duct which is called windbox. A windbox should be designed to supply combustion air to each burner evenly but, due to the complicated duct shape, flow distribution in the windbox is unbalanced and uneven supplies of combustion air to each burner are induced by these unbalanced flow distribution in the windbox. These flow patterns tend to make flame unstable, increase the formation of pollutants and lower the overall combustion efficiency. To prevent these disadvantages, flow patterns in the windbox should be investigated for the uniform flow distribution. In this study, computational simulation method was used to investigate the flow distribution in the windbox and measured the velocities at the exit of burners in the real windbox to compare with CFD results. The results show two significant flow patterns. One is that the flow rates of each burner are different from each other and this means that all burners operate in different conditions of air to fuel ratio. The other is that the flow distribution at the exit of each burner is not axi-symmetric although the burner shape is axi-symmetric and this increases the pollutant products like CO.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.85-92
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• 2005

Oil-fired power plants usually use several burners and the combustion air is supplied to each burner through the complicated duct which is called windbox. A windbox should be designed to supply combustion air to each burner evenly but, due to the complicated duct shape, flow distribution in the windbox is unbalanced and uneven supplies of combustion air to each burner are induced by these unbalanced flow distribution in the windbox. These flow patterns tend to make flame unstable, increase the formation of pollutants and lower the overall combustion efficiency. To prevent these disadvantages, flow patterns in the windbox should be investigated for the uniform flow distribution. In this study, computational simulation method was used to investigate the flow distribution in the windbox and measured the velocities at the exit of burners in the real windbox to compare with CFD results. The results show two significant flow patterns. One is that the flow rates of each burner are different from each other and this means that all burners operate in different conditions of air to fuel ratio. The other is that the flow distribution at the exit of each burner is not axi-symmetric although the burner shape is axi-symmetric and this increases the pollutant products like CO.

• 대한기계학회논문집B
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• 제28권6호
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• pp.652-658
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• 2004

In this paper, we report the numerical and experimental solutions of the axi-symmetric flows in the axial plane driven by an impingement of fluid from the bottom wall of a circular cylinder. We managed to visualize successfully the flow pattern shown on the vertical plane through the container axis. The numerical results are shown to compare well with the experimental results for the case of infinity Rossby number. The satisfactory agreement between the two results was possible when in the numerics the free surface was treated as a solid wall so that a no-slip condition was applied on the surface. The numerical solutions reveal that inertial oscillation plays an important role at small Rossby numbers, or at a larger background rotation.

• 한국철도학회논문집
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• 제3권4호
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• pp.229-236
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• 2000

In this study, the unsteady flow field induced by a high-speed train passing through a tunnel is numerically simulated by using an axi-symmetric Euler Equation. The modified patched grid scheme applied to a structured grid system was used to handle the relative motion of a train. The hybrid-dimensional approach which mixed 1D and axi-symmetric dimension was used to reduce the computation time and memory storage. By employing the hybrid-dimensional approach, a long tunnel as much as 5 km was able to be simulated efficiently. The results show that the maximum pressure rise in the tunnel by the entrance of the train is a function of both train speed and train-tunnel cross-sectional area ratio. The unsteady pressure fluctuation in the tunnel and around the train was also investigated in the real condition; Korean high-speed train on the Seoul-Pusan line.

• 한국산학기술학회논문지
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• 제1권2호
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• pp.21-26
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• 2000

플로포밍은 무절삭 점진성형공정으로 축 대칭 원형제품의 다품종 소량생산에 있어 스템핑이나 딥드로잉과 같은 박판성형 공정과 비교했을 때 매우 경제적이며 효율적인 공정이다. 본 연구에서는 기존 공정과의 품질비교를 통한 플로포밍 공정의 유용성 검토를 위해 현재 프레스 드로잉 공정으로 생산중인 자동차용 자동변속기 부품을 1-롤러 플로포밍 공정을 이용하여 대체 성형해 보았다. 실험결과 플로포밍 공정은 제조부품의 형상변화에 따른 설비변경 비용과 개발기간이 짧아 효과적인 유연 생산 시스템임을 알 수 있었다. 또한 플로포밍 공정을 프레스 드로잉 공정과 연계하여 성형하면 성형품의 정밀도와 생산성 향상에 매우 효과가 있음을 알 수 있었다.