• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.114-123
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• 2002

A supersonic rocket plum flowfield of kerosene/liquid-oxygen based propulsion system has been analysed using the Reynolds-averaged Navier-Stokes equations coupled with a 9-species 14-reaction finite-chemistry model. The result were compared with chemically frozen flow solution to investigate the effect of finite-rate chemistry on the plume flowfield. The computations were performed using a commercial CFD software, FLUENT 5. The finite-rate chemistry solution exhibited higher temperature caused by the reactions within the nozzle. All the chemical reactions within the plum were dominated only in the shear layer and behind the barrel shock reflection region where the temperatures are high and the effect of finite-rate chemical reactions on the flowfield was found to be insignificant. However, the present plume computation including the finite-rate chemical reaction within the plume has revealed major reactions occurring in the plum and their reaction mechanisms.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.197-202
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• 2014

The efficiency of a catalytic converter depends on the flow distribution across a system's chemically active substrate. If irregularities or non-uniform flow patterns exist, the system's conversion efficiency decreases, whereas the manufacturing cost increases. Therefore, it is important to analyze the internal flow of a catalytic converter. In this study, flow pattern measurements along the minor axis were recorded at the mid and exit planes of a ceramic honeycomb catalytic converter at flow rates of 37.8 l/s and 94.4 l/s. Flow distributions of the measurement plans were compared with an automotive company's computed velocity profiles. Measurements along the minor axis showed uneven velocity profiles. The ${\upsilon}$-velocity components between the honeycomb bricks were small but somewhat erratic opposite the intake side of the converter, however, they became flatter in measurements recorded near the intake entrance. For almost all velocity values, the computer model suggested velocities greater than the measured values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.130-135
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• 1995

본 연구에서는 30000rpm으로 회전하는 진공청소기 원심팬의 유동장을 임펠러, 디퓨저, 케이싱을 모두 고려하여 해석하였다. 또한 삼차원으로 배출되는 출구를 간단한 sink 패널로 모델하여 출구의 효과를 충분히 고려하였다. 해석된 유동장 자료를 이용하여 먼 거리에서의 음압을 예측하였다. 예측된 음압자료는 FFT를 이용하여 측정된 값과 주파수 영역에서 비교하였다. 또한 진공청소기 원심팬의 측정자료에서 보이는 광역소음특성이 임펠러에서 흘려지는 후류와류의 교란에 의한 임펠러와 디퓨저 깃의 비정상 힘이 주된 원인임을 밝혔다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.105-114
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• 2002

효율적인 난류 유동장 해석을 위해 CFDS 기법에 1개의 대수적 난류 모델과 2개의 1-방정식 난류 모델이 적용되었다. 대수적 난류 모델인 Baldwin-Lomax 난류모델과 1-방정식 난류 모델인 Baldwin-Barth, Spa lart-Allmaras 난류 모델을 비교하기 위해 2차원 유동에 대해서 2가지 경우, 3차원 유동에 대해서는 3가지 경우에 대해 해석하였다. CFDS 기법의 수치적 결과의 타당성은 실험치와의 비교를 통하여 입증하였다.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.107-118
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• 2011

This paper performs flow analysis of ultra-high speed vehicle inside the long distance tunnel. One and three dimensional hybrid mesh was used for describing moving motion and flow analysis of an vehicle inside a long distance tunnel which over 20 km. Flow analysis and aerodynamic drag measuring were performed by three dimensional mesh: around vehicle, and pressure waves of a tunnel was measured by one dimensional mesh: the other region where rare changing of flow pattern.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.58-66
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• 1999

The flow characteristics of supersonic ejectors is often subject to compressibility, unsteadiness and shock wave systems. The numerical works carried out thus far have been of one-dimensional analyses or some Computational Fluid Dynamics(CFD) which has been applied to only a very simplified configuration. For the design of effective ejector-pump systems the effects of secondary mass flow on the supersonic ejector flow should be fully understood. In the present work the supersonic ejector-pump flows with a secondary mass flow were simulated using CFD. A fully implicit finite volume scheme was applied to axisymmetric compressible Navier-Stokes equations. The standard two-equation turbulence model was employed to predict turbulent stresses. The results obtained showed that the flow characteristics of constant area mixing tube types were nearly independent of the secondary flow rate, but the flow fields of ejector system with the second-throat were strongly dependent on the secondary flow rate due to the effect of the back pressure near the primary nozzle exit.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.20-35
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• 1998

Characteristics of turbulent flow with wall transpiration is analyzed. The wall transpiration includes both of suction and injection and extends their range to 0~160 of absolute magnitude of Re$_{w}$ . Reynolds number based on inlet velocity also covers wide range of 3${\times}$$10^3$~8${\times}$$10^4$. The turbulent flow with wall transpiration induces change of wall boundary layer and rapid change of turbulent field. This, in turn, leads the change of whole flow field. For predicting this complicated flow field properly, newly modified $\kappa$-$\varepsilon$ model is utilized, which is formed by modifying dissipation rate equation. The modified $\kappa$-$\varepsilon$ model of Chien is also adopted for the comparison of model performance. Analysis shows the newly modified $\kappa$-$\varepsilon$ model is successfully able to reflect the characteristics of turbulent flow field with wall transpiration.ion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.4
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• pp.953-959
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• 1990

본 연구에서는 임의의 순간에서 난류유동장의 난류구조를 해석하기 위하여 Lumley의 특성 에디 분배법을 이용하였다. 이때 난류구조의 해석은 비등질성의 K-L 전개와 등질성의 푸리에 전개로 표현하여 그 수렴성, 레이놀즈 수의 영향 등 여러가지 특성을 연구하였다. 본 연구에서 선정한 비등질성 난류유동장은 Chambers등이 연구 한 랜덤력을 갖는 Burgers 방정식을 수치적으로 풀어서 얻었다. 이와 같은 난류유동 장을 K-L전개와 푸리에 전개로 표현할 때에 수렴성은 레이놀즈 수가 서로 다르고 또한 전개항의 수가 다를 때에 RMS 오차를 가지고 비교하였다.여기서 푸리에 전개 계수 들은 Galerkin 방법으로 구하였다.

• 전기의세계
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• v.9
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• pp.40-45
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• 1962

Laplace 및 Possion의 방정식을 만족하는 전장 및 자장으로 구성된 2차원 및 축대칭 3차원의 potential장을 물의 유동장을 이용한 fluid mapper로 상사해석함에 있어서 세극유로에 있어서의 유체전도율은 매질전도율로 압력은 전위로 유동장의 세기는 전장의 세기로, 유량밀도는 전류밀도로 각각 상사되며 또한 사상형에 있어서는 사상영역외에 존재하는 유선은 등자위선을 의미함을 논문에서 밝혔다. 이 논문에서는 사상형 fluid mapper의 전 유로 및 사상영역에 잇어서의 유체력학적 현상을 이론적으로 규명하여 이를 전기적 등가회로와 상사 해석함으로써 사상형 fluid mapper가 내포하고 있는 제량간의 상호관계를 명백히 하며 몇 가지 대표적인 사례를 들어 사상형 fluid mapper의 응용에 대하여 기술하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.1-16
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• 2009

In this paper, we introduce two-phase versions of RoeM and AUSMPW+ schemes. Both schemes are originally developed for the gas dynamic problems, and have shown superior accuracy, efficiency and robustness. A new shock discontinuity sensing term is derived from the mixture equation of state, which is commonly used in the RoeM and AUSMPW+ schemes for the stable numerical flux calculation. The developed two-phase versions of the schemes are applied to several liquid-gas, large property discrepancy two-phase test problems, including several shock stability test problems. The results show that both schemes maintain the merits exhibited in gas dynamic problems even in two-phase flows.