• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.312-313
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• 2005

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.58-58
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• 2017

점적 호스의 원통형 미로 구조물내의 유동특성을 분석하기 위해 금속판에 동일한 구조의 미로가 가공된 시험부를 활용하여 압력과 유량의 변화에 대한 실험을 CFD 해석하였다. 해석은 미로의 길이에 따른 유량 특성을 정밀하게 분석하기 위해 전체 미로에 구간별 총 8개의 배출구를 배치하고 밸브 조절을 통해 구간별 압력에 따른 유량을 측정함으로서 실험에 의한 압력과 유량의 관계를 검증하고 새로운 경질 미로를 설계하는데 응용하고자 한다. 경질 미로의 이론적인 해석에서 정밀도가 실험을 대신할 가능성이 있는지에 관심을 두었다. 점적관수의 경질 미로는 디자인을 달리함으로써 성능이 높고 미세한 스케일이 침착되지 않는 고성능의 점적관수 장치의 개발이 가능할 것으로 판단하였다. 미로 입구의 공급 유체 압력(Gauge pressure)을 0.5, 1.5, 2.5, 3.0 bar로 나누어 공급하였으며, 8개의 구간별 유출되는 유량은 전자저울에서 측정하였다. 향후 최적 미로의 새로운 설계를 위해 미로구조 전체를 CFD 해석하였고 그 결과를 실험치와 비교 분석하였다. 또한 경질 미로내 각 구간별 세부적인 유동구조를 분석하였고 해석결과와 실험결과를 통해 향후 새로운 경질 구조의 개발이 가능 할 것으로 판단되었다. 경질 미로의 입구압력에 따른 미로의 길이 #1과 #2에 대한 CFD 분석에서는 전체적으로 경질 미로에 압력이 증가할수록 미로의 유체 속도가 증가됨을 알 수 있었으며 이것은 #2에서도 거의 같은 양상을 나타내었다. 미로 통로에서는 와류로 인한 이물질의 멈춤 현상이 발생하지 않을 만큼 흐름이 원활함을 알 수 있었다. 미로의 길이 #3과 #4에 대한 CFD 분석과 미로의 길이 #5와 #6에 대한 CFD 분석에서는 압력이 증가하고 미로의 길이가 길어질수록 속도에도 영향을 미치고 있는 것으로 나타났으며 미로와 미로 사이의 넒은 통로에서는 유속이 크게 떨어지고 있음을 알 수 있었다. 따라서 이 부분에는 유체속의 이물질이 침착할 수 있는 가능성이 있으며 통로가 좁은 곳에서는 유속이 증가되는 것으로 나타났다. #7과 #8은 미로의 상하단으로 유출되는 부분의 차이이므로 실질적으로 해석의 결과는 차이가 없었다. 경질 미로에 대한 압력에 따른 미로의 길이별 유출량은 지수적인 반비례 현상을 나타내어 앞서 실험한 연구의 결과와 1~2% 오차 범위에서 잘 일치하였다. 따라서 점적 호스의 경질 미로에 대한 설계는 이론적인 해석을 통하여 새로운 디자인이 가능할 것으로 판단되었다. 경질 미로의 미로의 길이에 따른 CFD 분석의 결과는 실험적인 유출량의 값과 거의 일치하였다. 미로와 미로 사이의 넒은 통로에서는 유속이 크게 떨어져 이물질들이 침착될 가능성이 있었으며 실질적으로 넓게 설계하는 것이 유리하지 않을 것으로 판단되었다. 경질 미로에 대한 압력에 따른 미로의 길이별 유출량은 지수적으로 반비례 하였으며 점적 호스의 경질 미로에 대한 새로운 설계는 이론적인 해석을 통하여 가능할 것으로 판단되었다.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.22-28
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• 2006

Computer simulation of the air flow over an automotive vehicle is now becoming a routine process in automotive industry to assess the aerodynamic characteristics of a medium-size vehicle such as $C_d\;and\;C_1$ and aslo to investigate the possibility of improving aerodynamic performance of the vehicle as a preliminary design for the production line. Mainly due to its contribution in saving time and cost in the development of new cars, computer simulation of the air flow over a vehicle is usually done well before a production car is introduced to the market and in gaining more and more attention as powerful computer resources are getting readily available nowadays. To aerodynamically design a car is mainly related with reducing a drag coefficient of car. A well designed car usually has a $C_d$ value in the range of $0.3{\sim}0.4$. It is understandable that automotive industry is rushing to reduce a drag coefficient as reducing even a small fraction of the $C_d$ value can have an enormous overall impact on many areas. Actually, the present research model was able to achieve a $C_d$ value in the range of $0.3{\sim}0.36$ for flow velocities of $60km/h{\sim}100km/h$ by strategically removing the possible factor hazardous to lower $C_d$ value. Prediction of the medium-size vehicle aerodynamics using CFD was performed when an actual car model was in the development stage and three-dimensional modeling was also performed to optimize it as the best model in terms of the best aerodynamic performance.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.76-81
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• 2007

The objective of this study is to find the optimum design of a snubber using CFD analysis. Several dimensions such as snubber height(H), snubber diameter(D), buffer width and buffer angle are considered in this study. The present study shows that the CFD can be applied to study the pressure characteristics inside the snubber. The objective of the snubber design optimization are to minimize a pressure loss and the pulsation ratio. Numerical results such as particle track, pressure distribution and turbulent kinetic energy are used to analyze the critical area and pressure behavior inside the snubber. As a result, snubber model with H/D ratio of 3.23 and buffer angle of $40^{\circ}$ has a minimum pressure loss. On the other hand, snubber model with H/D ratio 4.41 and buffer angle $10^{\circ}$ has a minimum pulsation ratio.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.603-607
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• 2007

Recently, the frequency of unexpecting heavy rains has been increased due to abnormal climate and extreme rainfall. There was a limit to analyze one dimension or two dimension stream flow of domestic rivers that was applied simple momentum equation and fixed energy conservation. Therefore, hydrodynamics flow analysis in rivers has been needed three dimensional numerical analysis for correct stream flow interpolation. In this study, CFD model on FLOW-3D was applied to stream flow analysis, which solves three dimension RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as $k-{\backepsilon}$, RNG $k-{\backepsilon}$ and LES. Those numerical analysis results have been illustrated to bends and junctions by the turbulence energy effects, velocity of flow distributions, water level pressure distributions and eddy flows.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.166-167
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• 2010

최근 전기/전자 제품 개발에서 대용량, 소형화가 이루어지면서 제품 설계에 열유동 및 구조적 문제가 중요한 요소로 등장하였다. 열유동은 발열체와 공기의 흐름에 관련이 있기 때문에 시스템의 구조를 어떻게 설계 하느냐가 방열의 중요한 요소이다. 본 논문에서는 Ansys사(社)의 소프트웨어를 이용하여 연료전지용 PCS에 대한 열유동, 구조 및 강도 해석을 수행하였다. 3D설계는 CAD(Computer Aided Design) 소프트웨어인 Pro Engineer를 이용하였다. 설계된 3D 도면을 Ansys Multiphysics로 불러들여 구조 및 강도해석을 하였고 CFD(Computational Fluid Dynamics) 소프트웨어인 Icepak으로 열유동해석을 수행하였다.

• Journal of the Korean Society of Combustion
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• v.7 no.4
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• pp.10-20
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• 2002

This paper discusses effect of solid mass inventory on the hydrodynamic characteristics of circulating fluidized bed(CFB). Operating parameters of solid mass inventory and air flow rates were varied to understand their effects on fludization pattern. Experimental measurements were made in a CFB of which height and diameter are 3m and 0.05m respectively. Black SiC particles ranging from $100{\mu}m\;to\;500{\mu}m$ were employed as the bed material. Superficial gas velocity of riser and J-valve fluidizing velocity were in the ranges of $1.39{\sim}3.24m/s\;and\;0.139{\sim}0.232m/s$, respectively. The axial solid fraction and solid circulation rate of CFB were calculated based on the experimental data and compared with modellings through IEA-CFBC Model and commercial CFD code.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.185-188
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• 2006

An investigation of the ejector-jets focusing on its flow properties was carried out by varying the geometric parameters. The area ratio of the primary nozzle, AR that was tested in the present measurement was 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet, L/D had values of 3.41, 6.82, and 10.23. For the frame work of flow characteristics, the wall pressures distribution of ejector-jet was investigated by experiment for basic study of ejector-jet performance. In result, terminal shock location and existence of series of oblique shocks are recognized. In this study, CFD analysis was conducted at the same time. And as a result of comparison experiment data with CFD analysis, the physical phenomena of ejector-jets were estimated.

• The KSFM Journal of Fluid Machinery
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• v.8 no.4 s.31
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• pp.7-13
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• 2005

Although the globe is the most typical valve to control high pressure drop in piping system, it is very hard to figure out the characteristics of flow field in the globe valve caused by its complex geometry, So there is very few studies to find out flow characteristics of globe valve. In this study numerical analysis for flow field in the globe valve is carried out using the FLUENT code which is commercial CFD program. Pressure drop through the globe valve is also measured to verify the results come from numerical analysis. Comparing experiment with numerical analysis, two results are very close to each other.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.165-172
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• 2002

This paper discusses hydrodynamic characteristics of cold circulating fluidized bed(CFB) in different solid mass inventories. Operating parameters of solid mass inventory, primary air and J-valve fluidizing air were varied to find out the effect on the flow fludization pattern. Experimental measurements were made in a 3m tall CFB that has 0.05m riser diameter and black silica-carbonate of particle sizes from $100{\mu}m$ to $500{\mu}m$ were employed as the bed material. The operating conditions of superficial gas velocity and J-valve fluidizing velocity were in the ranges of 1.39~3.24 m/s and 0.139~0.232 m/s respectively. The axial solid fraction and solid circulation rate of CFB were observed and compared with modelling through IEA-CFBC Model and commercial CFD code.