• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.126-134
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• 2012

The Single Species, Unreacted Flow Model which is effectively applicable on the computational analysis of rocket exhaust flow is introduced in this paper. The basic concept of this model had been originated from chemically frozen analysis of hot air but it was complemented by compensating molecular weight and specific heat which was obtained CEA code analysis of exhaust plume. Comparing single species, unreacted model with the finite chemistry model, unreacted model can reduce calculation time to 1/5 while it makes similar simulation results.

• Journal of Korean Society of Transportation
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• v.19 no.1
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• pp.149-157
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• 2001

내부순환로 교통관리시스템은 기존의 국내 교통 시스템들과는 달리 충분한 수집체계와 정보제공 체계를 갖추고 있으며, 전략의 구체화와 현실적 실현, 즉 전략의 시스템화를 위해 많은 노력을 기울였다. 그런 노력의 일환으로 이 시스템에서는 다양하고 복잡한 돌발상황을 단순화하고 일반화하기 위해 Uniform Event Reaction Formula라 하는 개념을 사용하였다. 이 개념은 어떤 돌발상황이 발생하면 이로 인해 영향을 받는 반응 영역과 영향을 받지 않는 비반응 영역으로 분리한 후, 반응 영역은 예측을 통한 제어 관리를 수행하고, 비반응 영역은 통상적인 제어 관리만을 수행함을 의미한다. 그러나, 돌발상황에 따른 반응 영역과 비반응 영역의 결정에 필요한 돌발상황 처리시간 예측과 대기행렬 예측 모형은 내부순환로의 도로 및 교통환경에 적합한지 검증되지 않아 많은 시행착오가 예상된다. 특히, 돌발상황의 처리시간 예측은 동질대응 구간 결정의 가장 중요한 요소로서, 현재는 처리시간에 상당한 여유를 두어 운영할 계획이지만 궁극적으로는 내부순환로에 적합한 처리시간 예측 모형의 개발이 필요할 것으로 판단된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.449-452
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• 2008

Flow difference between reacting and non-reacting case in a swirl stabilized annular combustor is investigated using 3D Large Eddy Simulation with flamelet turbulent combustion model. The combustor of concern is the LM6000, lean premixed dry low-NOx annular combustor, developed by GEAE. Boundary conditions are based on experimental data. Heat release as a result of combustion put the dilatation of density in primary combustion zone highly increased so that the main swirl stream behind of a swirl cup stretched further downstream than that of non-reacting case. The oval shape of core flow in cross-section to flow direction, which clearly observed in non-reacting case, tends to be circle, and small vorticities in wide range in non-reacting case disappears, but the size of iso-vorticity increase in reacting case.

• Exercise Science
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• v.21 no.1
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• pp.111-120
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• 2012

The purpose of the study was to assess the effects of different cardiorespiratory fitness response to exercise training on cardiovascular disease and adipocytokine release and gene expression in abdominal obesity women. forty eight middle-age women were divided to a exercise-responder (n=34) group (ERG) and a exercise-nonresponder (n=14) group (ENRG) based on cardiorespiratory fitness after exercise training (12weeks, 1200 kcal/week, moderate-vigorous intensity, walking and jogging). Cardiorespiratory fitness was measured using maximal oxygen uptake with metabolic gas analysis and body composition was determined by bioelectrical impedance. We measured lipid and glucose profiles, blood adipocytokines and adipocytokine genes expression in adipose tissue. Waist girth (p=0.040), and %body fat (p=0.031) were significantly decreased in ERG than ENRG. Triglyceride (p=0.023) and systolic blood pressure (0.046) were significantly decreased in ERG than ENRG. Blood leptin (p=0.022) was significantly decrease in ERG than ENRG but leptin gene expression was decreased both groups (p<0.001). These results show that exercise-responder group improved cardiovascular disease risk factors and adipocytokine more than exercise-nonresponder group after exercise training. Moreover, exercise-nonresponders group show that obese indices and blood leptin and leptin gene expression in adipose tissue were decreased despite the failure to improve fitness. Therefore, regular exercise training seems to give health benefits although the failure to improve fitness.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.250-257
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• 2005

Large eddy simulation{LES) methodology used to model a bluff-body stabilized non-reacting flow. The LES solver was implemented on parallel computer consisting 16 processors. To verify the capability of LES code, the results was compared with that of Reynolds Averaged Navier-Stokes(RANS) using $k-{\epsilon}$ model as well as experimental data. The results showed that the LES and RANS qualitatively well predicted the experimental results, such as mean axial, radial velocities and turbulent kinetic energy. However, in the quantitative analysis, the LES showed a better prediction performance than RANS. Specially, the LES well described characteristics of the recirculation zones, such as air stagnation point and jet stagnation point. Finally, the unsteady phenomena on the Bluff-body, such as the transition of recirculation region and vorticity, was examined with LES methodology.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.05a
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• pp.28-38
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• 1994

분류층 가스화기 설계를 위한 일차연구로서 가스화기 이차공기 주입방법에 따른 비반응 난류장에 대한 수치해석을 검사체적에 기초한 유한차분방법을 이용하여 수행하였다. 압력과 속도의 연계문제는 SIMPLEC 알고리즘을, 레이놀즈 전단력은 k-$\varepsilon$ 난류모델을 사용하였다. 입자궤적 계산은 공기역학적 항력만을 고려하였으며 비선형적인 공기저항력에 의한 난류변동상관모델은 고려치 않았다. 이차공기 주입방법(parallel injection과 nonparallel 3$0^{\circ}C$ injection)에 따른 수치해석을 수행하여 Ar tracer의 질량분율에 대한 실험자료와 비교하여 만족할 만한 결과를 얻었으며 이차공기의 주입각 및 기타 제반변수에 따른 유동장 변화를 분석하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.28-37
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• 2004

A two-dimensional direct numerical simulation was performed to investigate the evolution and vortical structure of a single vortex in reacting and non-reacting jet flow fields. A predictor-corrector-type numerical scheme with a low Mach number approximation was used, and a two-step global reaction mechanism was adopted as the combustion model. Through the comparisons of single vortex behaviors in reacting and non-reacting jet flow fields, it was found that the evolution characteristics and vortical structure of the single vortex were significantly influenced by a outer vortex that was generated from the buoyance effect as well as the chemical heat release. Furthermore, it was also identified that the differences of the vortical structure in reacting and non-reacting jet flow fields were mainly attributed to the thermal expansion, Baroclinic torque and buoyance effect.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.11a
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• pp.5-14
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• 1995

본 연구는 석탄가스화기내의 비반응 유동장에 대한 연구로서, 순수유동장 및 미분탄입자를 포함한 이상유동장에 대한 전산해석을 수행하였다. 가스화기내의 물리적 현상을 기술하는 Navier-Stokes 방정식을 유한차분법에 의하여 해석하고 그 결과를 나타내었다. 특히 선회유동의 영향에 의한 미분탄입자의 거동 및 재순환영역의 특성에 대하여 상세히 고찰하였다. 해석결과에 의하면 가스화기내에서는 몇개의 재순환영역이 형성됨을 알 수 있었다. 비반응유동장의 해석결과이지만, 선회유동은 화염안정화에 긍정적인 영향을 줄 수 있을 것으로 추측되는 결과를 보였다.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.137-144
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• 1997

Turbulent swirling cold-flow in a cyclonic gasifier has been analyzed by numerical analysis. Comparison of two dimensional and three dimensional analyses has shown that concept of equivalent slit is appropriate for the two dimensionalization of three dimensional phenomena. Flow characteristics have been scrutinized by varying swirl number which is a crucial parameter in determining the flow pattern of the cyclonic gasifier. Reactive flow field has been estimated by using theoretical swirl number and equivalent slit width for reactive flow. Results show that proper flow field for the reactive coal gasification can be formed by controlling the exit area and azimuthal location of coal burners.

• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.87-97
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• 2000

The effects of environmental conditions, initial dissolved oxygen concentrations, pH, and the presence of electron carrier vitamin $B_{12}$, on the reduction rate of Tn by $Fe^0$ was quantitatively analyzed using a batch reactor In all experiments, TNT reduction was best described with a first order reaction and the reduction rate decreased with the increase in the initial DO concentration. However, the specific reaction rate did not decrease linearly with the increase in the initial DO concentration. In the presence of HEPES buffer 0.2 and 2.0 mM(pH 5.7$\pm$0.2), the specific reaction rate increased more than 5.8 times, which showed reduction rate is rather significantly influenced by the pH of the solution. To test the possibility of reaction rate enhancement, well-known electron carrier(or mediator) , vitamin $B_{12}$, has augmented besides $Fe^0$. In the presence of 8.0 $mu\textrm{g}$/L of vitamin $B_{12}$, the specific reaction rate increased as much as 14.6 times. The results indicate that the addition of trace amount of vitamin $B_{12}$ can be a promising rate controlling option for the removal of organics using a $Fe^0$ filled permeable reactive barrier.