• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.45-52
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• 2003

Detailed flowfield resulting from the secondary sonic gas injection into a divergent section of supersonic conical nozzle has been numerically investigated. The three-dimensional flowfield associated with the bow-shock/boundary-layer interaction inside the nozzle has been solved by Reynolds-averaged Navier-Stokes equations with an algebraic and $\kappa$-$\varepsilon$ turbulence model. The numerical results have been compared with the experimental results for the identical flow conditions, and it is shown that the comparison is satisfactory Effects of different injection pressures of the secondary jet on the shock/boundary-layer interactions and the overall flow structure inside the nozzle have been investigated. The vortex structures behind the shock interaction and wall pressure variations have also been studied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.187-195
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• 2012

This paper deals with numerical computations of cryogenic flows around turbopump inducer. Firstly, we introduce numerical methods to compute compressible/incompressible cryogenic two-phase flow. As a validation problem, computation results of 2 dimensional/axi-symmetric cryogenic flow will be presented. In this process, various cavitation model will be compared. Finally, numerical simulation of 3 dimensional turbopump inducer will be presented.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.29-36
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• 1997

자유흐름장에 놓여 있는 회전 와류쌍을 음원으로 갖는 비정상 유동장에서 사극음원이 음장에 미치는 효과를 알아보기 위해 이차원 음장 수치해석을 시도하였다. 비압축성 유동장에 대한 비정상 수력정보를 기반으로 오일러식에서 교란 압축성 소음항을 도출하였다. 원거리 자유 경계면은 비반사 경계조건을 이용하여 매우 안정된 해를 얻을 수 있었다. 계산된 결과들은 MAE 방법과 비교하여 정확도를 입증하였다. 본 연구를 통해 비압축성 압력교란을 원천항으로 하여 물체가 존재하지 않는 경우에도 사극음원에 의한 음장을 수치적으로 계산이 가능함을 입증하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.363-367
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• 2016

A test section of a supersonic wind tunnel was designed for the analysis of flow characteristics over a backward-facing step with Mach 1.0 slot injection in a supersonic flow of Mach 2.5. The cavity flow of a high-speed vehicle is very complex at supersonic speed, so it is necessary to do experiments using supersonic wind tunnels to verify numerical analysis methods. The previous 2D symmetrical nozzle was replaced with an asymmetrical nozzle. The inviscid nozzle contour was designed using Method of Characteristics (MOC), and the boundary layer thickness correction was reflected by experimental data from the wind tunnel. The results were compared with a CFD analysis. The PID control system was changed to be based on the change of tank pressure. This improved the control efficiency, and the run times of supersonic flow increased by about 1 second. The flow characteristics over a backward facing step with slot injection were visualized by a Schlieren device. This equipment will be used for an experimental study of the film cooling effectiveness over a cavity with various velocities, mass flows, and temperatures.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.156.2-156
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• 2002

• 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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.266-267
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• 2017

A numerical investigation of the stage separation behavior of two-body vehicle focusing on its flow characteristics were carried out. For this simulation, separation of a booster from vehicle was modeled by a chimera grid system and calculated by using commercial code, CFD-FASTRAN$^{TM}$. Consideration of a spring force, gravity and relative acceleration of a booster was the essential factor that simulates the realistic situation. In this study, It was validated that the booster separation time decreases with increase in flight mach number and angle of attack. In view of the results so far achieved, it was expected that the dynamics modeling and boundary condition set up applied in this study will be helpful in a estimation of a safe stage separation and event sequence of flight test.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.4
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• pp.273-281
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• 2001

In this paper, we report the experimental and numerical results on spin-up flows in a rectangular container of the aspect ratio 2. The Ekman pumping models used in the numerical study are of 1st- and 2nd- order. We also investigate flows obtained without any pumping model. In the experiment, the classical PIV method is used. It is shown that the results given by the 1st-order and 2nd-order models are in good agreement with the experimental result, whereas the non-pumping model shows a significant discrepancy.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.341-344
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• 2009

본 연구에서는 허브 대 팁의 비가 큰 원심형 압축기의 성능시험을 수행하였으며, 이를 수치해석 결과와 비교하였다. 압력비의 경우 작동 회전수에서 성능시험과 수치해석의 결과의 경향이 일치하는 것을 확인하였다. 성능시험에서 임펠러의 성능은 매우 높게 나타났으나, 1단 및 2단 디퓨져에서 손실이 발생하여 전체적인 압력비 및 효율이 떨어지는 것을 확인하였다. 수치해석을 통해 내부 유동장을 확인한 결과 1단 디퓨져 및 2단 디스월러에서 격렬한 2차 유동으로 인한 유로차폐효과가 주 손실원인임을 확인하였다.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.50-55
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• 1996

A numerical simulation on a primary calcinator of porcelain was performed with using Fluent to calculate the heat efficiency by studying velocity vector and temperature profile according to variables such as the location of outlet and porcelain. Control-Volume based Finite Difference Method and Up-wind scheme are used for discretization of differential equation. SIMPLEC Algorithm and standard k-$\varepsilon$ turbulent model are selected to resolve the pressure-velocity coupling and the turbulent. The result of simulation showed that the whole velocity vector field in a calcinator was varied greatly according to the location of outlet. But the whole temperature profile at each zone was still high regardless of the location of outlet because of the radiation. But the temperature of a case with a outlet at sidepart of preheating or cooling zone was little high compared to the case with a outlet on the top of preheating zone. The velocity vector field and temperature profile in a calcinator were almost not affected by the location of porcelain, but the temperature inside a porcelain was much affected according to the place where it was located. The heat efficiency in a calcinator was 44.6% and the gas temperature in the outlet was about 1000 K.