• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.70-78
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• 2014

A numerical study has been conducted to investigate flow and heat transfer characteristics of supersonic second throat exhaust diffusers for high altitude simulation. By changing pressure and configuration, flow and cooling characteristics of the diffuser have been studied. At the normal operation of the diffuser, there were high temperature regions over 3,000 K without cooling, especially near wall and in subsonic diffuser part. If the cooling system of the diffuser is added, flow velocity is increased due to the cooled wall temperature.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.23-30
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• 2009

The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Furthermore, numerical simulations for supersonic shock boundary layer interaction with a bleed region were performed and their results were compared with the existing computational results.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.8-15
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• 2020

In this paper, we propose a container wall and its boundary layer insulation design method that can maintain the temperature inside the spacecraft shipping container constantly under the condition that the heat or the external temperature changes severely to safely transport the satellite to the launch site. We will examine if the temperature inside the satellite shipping container is kept constant through the heat flow analysis and the satellite heat transfer analysis for the external environment of the satellite shipping container. Through the flow analysis inside the container, the flow distribution around the satellite in the container is analyzed, and the auxiliary fan, air conditioning system and special grill guide structure design for improving and optimizing heat flow performance are proposed.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.298-303
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• 1997

실제의 격납건물의 구조는 하부 원통형의 구조를 가지는 영역과 상부 돔 형태와 굴뚝 형태의 구조를 가지는 영역으로 나눌 수 있다. 하부 원통형의 구조만을 고려한다면, 고온의 철제 벽면과 콘크리트 벽면 사이의 gap 크기에 비해서 원통의 반지름이 상대적으로 매우 큰 값을 가지기 때문에 2차원 무한평판으로 가정하는 것이 가능하다. 그러나 돔 및 굴뚝 영역에서는 높이가 높아질수록 돔 단면직경이 감소하고 굴뚝 영역도 유동단면적이 작은 원통의 구조를 가져 2차원 무한평판의 가정에 많은 무리가 따른다. 앞에서 명시한 세 가지의 격납건물 형태에 있어서 ASPWR의 경우는 굴뚝을 포함한 영역까지도 무한평판으로 가정하는 것이 가능하나(돔에서의 열전달 단면적이 하부의 열전달 단면적에 비해 매우 작다는 가정을 한다면) 나머지 AP600과 HWRF의 격납건물에 있어서는 상부까지도 무한평판 가정을 사용하는 것에는 무리가 있다. 본 연구에서는 일반적인 유체해석 코드인 FLUENT V4.3을 이용하여 실제 격납건물 구조에 대한 분석을 시도하여 무한평판 구조에 대한 가정이 과도한 열전달량을 예측하고 있음을 확인하였다.

• Journal of KSNVE
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• v.10 no.4
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• pp.602-609
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• 2000

When an axisymmetric body moves through air the boundary layer near the stagnation region remains laminar and subsequently it goes through transition to turbulent. The experimental investigation described in this paper concerns the characteristics of wall pressure fluctuations at the initial stage of boundary layer flow including transition. Flush-mounted microphones are used to measure the wall pressure fluctuations at the transition and turbulent boundary layer region of a blunt axisymmetric body in the low noise wind tunnel. It if found from this study that the wall pressure fluctuations in the transition region is higher than that in the turbulent region.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.2-5
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• 2011

This paper presents a numerical study on multiphase flows induced by wall adhesion The CSF(Continuum Surface Force} model is used for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing As an application of the present method, the effects of wall adhesion are numerically simulated with the CSF model for a shallow pool of water located at the bottom of a cylindrical tank. Two different cases are computed, one in which the water wets the wall and one in which the water does not wet the wall. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows induced by wall adhesion.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.60-68
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• 2005

For study on the unsteady wall interference effect, flows around a forced oscillating airfoil in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The Spalart-Allmaras one-equation model is employed for the turbulence effect. The computed results of the oscillating airfoil having a thin wake showed that the lift curve slope is increased and the magnitude of hysteresis loop is reduced by the interference effects. Since the vortex around the airfoil is generated and convected downstream faster than the free-air condition, the phase of lift, drag and pitching moment coefficients was shifted. The pressure on the test section wall shows harmonic terms having the oscillating frequency contained in the wail effect.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.479-484
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• 2000

A Navier-stokes based finite volume method has been developed to analyze an incompressible, steady state, turbulent wall-jet flow. The standard k-e model, the RNG ${\kappa}-{\varepsilon}$ model and their nonlinear counterparts are adopted as a closure relationship. Comparison with the experimental data shows that a linear ${\kappa}-{\varepsilon}$ model performs satisfatorily for two-dimensional wall-jet flows. However, as the flow becomes three dimensional, the linear model fails to predict the spanwise jet growth accurately and the nonlinear model needs to be adopted to capture three-dimensional flow characteristics.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2002.11a
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• pp.79-84
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• 2002

디지털 삶에서 인간들은 더 이상 보호막으로써의 건축 환경이 아닌 함께 상호작용 할 수 있는 감성반응 환경을 요구한다. 즉, 실내 공간은 사람들의 요구를 충족시키거나 사람들의 기분을 만족시키기 위해 건물이 마치 살아 있는 유기체처럼 쉬지 않고 변하는 공간이다. 그러나 건축공간의 물리적 특성의 한계에서 유동적인 감성반응 환경의 요구를 충족시키는 데에는 많은 한계점이 따른다. 그래서, 본 연구에서는 이러한 한계점을 극복하기 위해 디지털 환경을 이용한 가상공간에서 실행하였다. 이는 실제공간에서의 시행착오를 줄일 수 있을 뿐만 아니라 빠른 시간 내에 인간의 반응을 연구할 수 있다. 특히, 본 연구에서는 감성반응의 실내배색에 의해 실내공간에서의 디지털 벽면의 디자인을 가상공간에서 개발하여 거주자의 감성 반응을 평가하는 것을 연구 목적으로 두었다. 이와 같은 거주자의 감성반응형 환경 디자인은 미래의 디자인의 패러다임이 될 것이다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.945-956
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• 2000

The axisymmetric bodies considered in this study have hemispherical and ellipsoidal noses. The near-field pressure fluctuations over each nose model at $Re_D=2.43{\times}10^5$ were investigated in the laminar separation region and developing turbulent boundary layers using a 1/8' pin-holed microphone sensor. The wall pressure fluctuations were also measured in an axisymmetric boundary layer on a cylinder parallel to mean flow at a momentum thickness Reynolds number of 850 and a boundary layer thickness to cylinder radius ratio of 1.88.