• 대한기계학회논문집B
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• 제28권5호
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• pp.553-559
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• 2004

Stratified flow past a three-dimensional obstacle such as a sphere has been a long-lasting subject of geophysical, environmental and engineering fluid dynamics. In order to investigate the effect of the stratification on the near wake, in particular, the unsteady vortex formation behind a sphere, numerical simulations of stratified flows past a sphere are conducted. The time-dependent Navier-Stokes equations are solved using a three-dimensional finite element method and a modified explicit time integration scheme. Laminar flow regime is considered, and linear stratification of density is assumed under Bossiness approximation. The computed results include the characteristics of the near wake and the unsteady vortex shedding. With a strong stratification, the separation on the sphere is suppressed and the wake structure behind the sphere becomes planar, resembling that behind a vertical cylinder.

• 대한기계학회논문집
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• 제10권5호
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• pp.618-624
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• 1986

본 논문에서는 최근까지 제시된 동방향 성층이상유동의 직접접촉응축열전달계 수에 대한 여러가지 상관관계식들을 검토하고 실험결과와 비교하여 적절한 관계식을 제시하고자 한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.565-570
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• 1998

An interfacial condensation heat transfer phenomenon in a steam/water countercurrent stratified flow in a nearly horizontal pipe has been experimentally investigated. The present study has been focused on the measurement of the temperature and velocity distributions within the water layer. In particular, the water layer thickness used in the present work is large enough so that the turbulent mixing is limited and the thermal stratification is established. As a result, the thermal resistance of the water layer to the condensation heat transfer is increased significantly. An empirical correlation of the interfacial condensation heat transfer has been developed. The present correlation agrees with the data within $\pm$15%

• 한국자동차공학회논문집
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• 제6권6호
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• pp.202-209
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• 1998

For development of SDI(Spark-ignited Direct Injection) engine, stratified mixture formation with adequate strength at spark plug was required in wide range of engine operating conditions. So, spray structure under high ambient pressure and spray distribution after impingement on piston bowl in motoring engine was visualized by using laser equipments. Also, incylinder bulk flow structure was measured by using PIV (Paiticle Image Velocimetry) system. Counter-rotating tumble port and bowl piston was found effective to conserve bulk motion directed to spark plug in compression stroke. In addition, mask attached near valve seat in intake port was proposed to attenuate conventional tumble component and enhance counter-rotating tumble component.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.882-895
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• 2006

Surface and interfacial waves in two superposed horizontal inviscid fluids of finite depths are studied. The flow is induced by translating a vertical rigid plate with a prescribed velocity. Analytical solutions that accurately predict the motion of the free surface and the interface are obtained by using a small-Froude-number approximation. Three different velocities of the plate are considered, while flows induced by any arbitrary motion of the plate can be easily analyzed by a linear superposition of the solutions obtained. It is shown that pinching of the upper layer can occur for a sufficiently thin upper layer, which leads to its rupture into small segments. Other interesting phenomena, such as primary and secondary wiggles generated on the interface near the wavemaker, are discussed.

• 해양환경안전학회지
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• 제18권3호
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• pp.279-285
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• 2012

LNGC 주기관의 크랭크 챔버 내 유증기 폭발 방지를 위해 기존의 이산화탄소 가스인젝터가 부착된 오일미스트 감지기 외에 불활성가스 시스템을 설치할 필요가 있다. 특히, LNGC 선박은 액체질소를 손쉽게 확보할 수 있는 장점이 있기 때문에 액체질소를 이용한 불활성가스 시스템을 도입하기 위한 설계 기초 단계로서 해석적 연구를 시행하였다. 또한 액체질소 최소 소모량 시스템을 개발하기 위하여 층상류 모델을 적용하였으며, 층상류 흐름에 미치는 유로관경, 포화압력과 선박동요에 따른 배관 기울기 등의 영향에 대해서도 조사하였다. 또한 질소와 같은 극저온 유체들과 여기에 사용된 예측 모델과의 비교 검토를 통하여 극저온 유체에 대해서도 모델의 유효성을 검증하였으며, 액체질소 불활성가스 시스템의 액체질소를 가스로 상변환 시키는데 소요되는 가열기의 열부하도 예측할 수 있었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.315-317
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• 2006

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 추계학술발표회요약집
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• pp.133-133
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• 1998

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.151-151
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• 1999

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 1998년도 봄 학술발표회 프로그램
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• pp.68-71
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• 1998