• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.231-236
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• 2015

Investigations into cavity flows have been conducted for decades now, most of them being about zero-pressure-gradient flows entering a cavity on a straight wall. However, the flow over curved walls in real-life situations has not been fully investigated. As cavity flows on curved walls exert centrifugal force, these walls are likely to possess different features from straight walls. To verify this possibility, this study investigated cavity flows on curved walls. Using numerical method, the effect of two variables, namely, radius of curvature on a curved wall and inlet Mach number, were investigated for subsonic and supersonic cavity flows. The result demonstrates that the value of the peak pressure generated inside the cavity increases with the decrease in the radius of curvature on a curved wall or an increase in the inlet Mach number. The total pressure loss in the cavity also results in an increase in the cavity drag.

• Journal of the KSME
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• v.29 no.4
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• pp.376-384
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• 1989

압축성 유동은 유동의 속도(Mach 수)에 따라, 아음속에서 초음속으로 바뀜에 따라 지배 방정 식의 형태가 바뀜은 물론이고 천음속에서는 아음속과 초음속이 공존하므로 지배방정식 자체도 두 가지 형태가 공존하는 어려움이 앞선다. 또한 압축성 유동장에서는 비압축성 유동장에서는 없는 충격파를 전후하여 유동변수들의 큰 불연속이 존재하게 되고, 이러한 불연속선을 유한한 크기의 계산격차를 사용하여 정확하게 해석한다는 것이 그렇게 쉬운 일이 아니다. 또한 저속의 비압 축성 유동에 비하여 일반적으로 보다 많은 독립변수들을 동시에 다루어야 하므로 대형컴 퓨터 용량과 빠른 계산속도를 요구하게 되며 국내에서는 2∼3년 전까지만 하더라도 실질적인 연구가 매우 어려운 실정이었다. 따라서 본 글에서는 최근 들어 대학실험실에 고성능 퍼스널 컴퓨터의 도입과 더불어 활발하게 진행되고 있는 압축성 유동의 수치해석 연구에 대하여 그 동 안의 국내연구 결과들을 모아 분류, 정리해 보고 앞으로의 연구에 대하여 간단히 언급해 보고자 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.413-422
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• 2005

In this paper, numerical results for 3-D supersonic turbine flow have been firstly compared with the experimental results to verify results computed by $Fine^{TM}/Turbo$. It was found that $Fine^{TM}/Turbo$ can accurately predict flow characteristics within supersonic turbine. Next, an grid system for 3D turbine flow was optimized selected through grid independency test. Finally the effect of axial gap between rotor and nozzle and chamfer angle of blade edge on the flow characteristics within 3-D supersonic turbine was analyzed with Frozen Rotor method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.359-362
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• 2006

Infra-red thermography was conducted to understand a heat transfer characteristic on a surface protruded to a supersonic flowfield. Surface temperature distribution was obtained under the constant heat flux condition with a infra-red camera and the convective heat transfer coefficient distribution was calculated. Finally, two dimensional distribution of heat transfer coefficient on a surface around a cylinder body was derived.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.37-40
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• 2012

EDISON CFD 수치 해법 기법을 바탕으로 초음속 유동장 속에서 spike가 부착된 무딘 물체에 대하여, spike 형상 변화에 따른 압축성 효과에 의한 항력 변화 추이를 고찰하였다. Spike의 길이 따른 항력 변화 추이를 살펴보았다. Spike의 길이가 Main body와 특정한 비율을 가질 때 항력이 최소가 된다. 이를 기준으로 spike 길이가 특정 길이만큼 줄어들거나 늘어날 경우에 각각 1.35%, 4.95% 항력이 증가하였다. 이러한 자료들은 초음속 유동장에서 무딘 물체에 가해지는 압축성 효과에 의한 저항을 최소화하기 위한 spike 설계 시 중요한 견해를 제공한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.160-163
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• 2010

We performed three-dimensional CFD analysis to investigate the effect of the nozzle-rotor axial gap of a partial admission supersonic turbine on the stage performance and the flow field. The computations are conducted for five axial gaps using flow analysis program, $FLUENT^{TM}$. The results show that the axial gap between nozzle and rotor give the effect on the mass flow rates of tip leakage and the flow angle at the rotor outlet.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.130-134
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• 2010

The effects of design parameters of supersonic ejector system under the assumption of constant pressure mixing were performed. Design parameters were mass flow rate ratio, area ratio between primary and secondary flow, and primary Mach number. 1-D theoretical performance of ejector in terms of pressure ratio and contraction ratio with and without loss mechanism such as diffuser efficiency and friction were considered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.362-366
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• 2010

Numerical Analysis of two-stage supersonic turbines were conducted, and the results were analyzed. $FLUENT^{TM}$ commercial flow analysis package was employed for the calculation of the turbine. Characteristics of the turbine performance were investigated according to the overlap height and existence of the shroud at the second rotor blade through the calculations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.345-348
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• 2008

The subcavity passive control technique is used in present study. Cavity-induced pressure oscillation has been investigated numerically for a supersonic three-dimensional flow over rectangular cavities at Mach number 1.83 at the cavity entrance. The three-dimensional, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme. The results showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.349-352
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• 2010

A study is analyzed on the transient flow of supersonic diffuser and performed on the of supersonic diffuser with Computational Fluid Dynamic. The flow field of supersonic diffuser is calculated using Axisymmetric two-dimensional Navier-Stokes equation with $k-{\epsilon}$ turbulence model. The transient simulation is compared in terms of mach number and temperature of vacuum chamber according to the chamber pressure of starting transient on Liquid rocket engine.