• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.332-335
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• 2008

The purpose of this study is analysis of flow field where is around of injector of supersonic combustor which is bluff-body stabilized flame and hyper-mixer type of supersonic combustor injector by using hydrogen or hydrocarbon fuel. Various schemes are evaluated to supersonic backward step flow filed with massive separation region in validation step. Compounded scheme of 5th-order TVD-MUSCL, Roe FDS, S-A DES/DDES has a good performance in base and base-bleed flow.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.193-195
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• 2011

An abrupt increase of duct cross-section is frequently encountered in pressure reducing devices, valves of internal combustion engines and in gas pipelines. Supersonic flow in a rectangular duct passing an abrupt increase of cross-section is studied numerically. The behavior of base pressure of the dead-air region at sudden enlargement of the duct is clarified. This investigation concerns the determination of the base pressure, which is independent of the size of the enlarged part. Several flow patterns are identified with different enlargements according to the ratio between the downstream ambient pressure and the upstream reservoir pressure. Base pressure and the resulting shock-structure are highly depending on the size of duct enlargement. For a given duct, base pressure tends to minimum for a particular pressure ratio. In addition, the locations of secondary separation and reattachment points of the jet plume are found with respect to different duct enlargements.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.615-619
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• 2009

(+)-$Tr{\ddot{o}}ger$'s base in $Tr{\ddot{o}}ger$'s base racemates that inhibits thromboxane A2($T{\times}A2$) synthase has been used to treat arteriosclerosis. Separation of (+)-$Tr{\ddot{o}}ger$'s base by chromatography has become a major concern. However separation experiments of (+)-$Tr{\ddot{o}}ger$'s base need time and consumables so that simulation with Aspen Chromatography could save time and costs by predicting the efficiency of separation. Injection amount and eluent flow rate were varied to compare the resolutions and yields of TB(-) and TB(+). Highest resolution and yield were attained at the eluent rate of 0.25 mL/min. Isotherms representing the relationship between mobile phase concentration and stationary phase concentration were changed to get the best separation with Ideal Adsorbed Solution(IAS) Statistical Lanmuir isotherms.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.318-320
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• 2011

Numerical study was conducted to simulate the heat transfer on the real launch vehicle base. Three different base temperatures were chosen, to simulate the heat accumulation on the base. Moreover, six different pressure ratio conditions were used to express the different air conditions. As a result, the table that can used to estimate the base heat fox along the base temperature and pressure condition was made.

• Wind and Structures
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• v.11 no.5
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• pp.377-389
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• 2008

An experimental investigation has been conducted to determine the effectiveness of base shield plates in reducing the drag of a rough circular cylinder in a cross flow at Reynolds numbers in the range $3{\times}10^4{\leq}Re{\leq}10.5{\times}10^4$. Three model configurations were investigated and compared: a plane cylinder (PC), a cylinder with a splitter plate (MC1) and a cylinder fitted with base shield plates (MC2). Each configuration was studied in the sub and supercritical flow regimes. The chord of the plates, L, ranged from 0.22 to 1.50D and the cavity width, G, between the plates was in the range from 0 to 0.93D. It is recognized that base shield plates can be employed more effectively than splitter plates to reduce the aerodynamic drag of circular cylinders in both the sub- and supercritical flow regimes. For subcritical flow regime, one can get 53% and 24% drag reductions for the MC2 and MC1 models with L/D=1.0, respectively, compared with the PC model. For supercritical flow regime however, the corresponding drag reductions are 38% and 7%.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.1
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• pp.15-19
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• 2000

This study estimates the baseflow using the separation of daily streamflow hydrograph. For the separation of hydrograph, we used standard method. This method was presented by Institute of Hydrology in 1980. For the estimation of baseflow, we estimated the parameters of model using the relation of the catchment properties and the baseflow index. The baseflow is estimated by the results of the separation of daily streamflow hydrograph and is estimated 20.0%∼39.4%. Baseflow rates is high for larger catchments but low for smaller catchments. As the results of this study, there is no relation between rainfall and baseflow rates.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.45-48
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• 2003

The plume interference is a complex phenomenon, consisting of plume-induced boundary layer separation, separated shear layer, multiple shock waves, and their interactions. The base knowledge of plume interference effect on powered missiles and flight vehicles is not yet adequate to get an overall insight of the flow physics in plume-freestream flow field. Computational studies are performed to better understand the flow physics of the plume-induced shock and separation for Simple, Rounded, Porous-extension test model configurations. The present study simulates highly underexpanded exhaust plume effect on missile body at the transoni $c^ersonic speeds. In order to investigate the plume-induced separation phenomenon, Simple, Rounded and Porous-extension plate are attacked to the missile afterbody. The computational result shows that the rounded afterbody and the porous-extension wall attached at the missile base can alleviate the plume-induced shock wave and separation phenomenon and improve the control of the missile body.dy.

• Journal of computational fluids engineering
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• v.20 no.2
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• pp.16-22
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• 2015

The pressure is generally lower than that of the freestream at the base of a missile body due to the energy loss by the flow separation around the edge of the base. The base pressure changes in the presence of the thrust jet due to the interaction between the base flow of the missile and the jet flow. In this study, behavior of the missile base pressure by the change of the jet exit pressure and the freestream condition is investigated using the CFD(Computational Fluid Dynamics) method. Effects of the grid type and the freestream condition are tested. The results are compared with the semi-empirical predictions and the flight test data. The CFD results agree well with the flight test data. The semi-empirical predictions overestimate the base pressure when jet thrust is strong for low freestream speed.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2851-2856
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• 2007

Flow patterns in the presence of two identical nearby circular cylinders at =100 were numerically studied. We considered all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. Eight distinct flow patterns were identified based on vorticity contours and streamlines, which are Base-Bleed, Biased-Base-Bleed, Shear- Layer-Reattachment, Induced-Separation, Vortex-Impingement, Flip-Flopping, Modulated Periodic, and Synchronized-Vortex-Shedding. Collecting all the numerical results, we propose a general flow pattern diagram for flows past the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use this diagram to distinguish flow patterns in the presence of two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.8
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• pp.724-732
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• 2007

Flow patterns in the presence of two identical nearby circular cylinders at Re=100 were numerically studied. We considered all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. Eight distinct flow patterns were identified based on vorticity contours and streamlines, which are Base-Bleed, Biased-Base-Bleed, Shear-Layer-Reattachment, Induced-Separation, Vortex-Impingement, Flip-Flopping, Modulated Periodic, and Synchronized-Vortex-Shedding. Collecting all the numerical results, we propose a general flow pattern diagram for flows past two nearby cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use this diagram to distinguish flow patterns in the presence of two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.