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배대석(Dae Seok Bae),김남식(Nam Shik Kim) 한국마린엔지니어링학회 2003 한국마린엔지니어링학회 학술대회 논문집 Vol.2003 No.-
The Particle Image Velocimetry(PIV) with liquid crystal tracers is used for visualizing and analysis of bubbly flow in a stratified temperature environment. This method allows full field temperature and flow analysis. In the present work, the temperature measurement of bubbly flow is studied by the application of liquid crystal thermometry. The performance of color-to-temperature transformation of the thermochromic liquid crystals is evaluated by using the calibration technique with neural networks. The measured temperature distributions indicate the temperature mixing characteristics of bubbly flow. This paper describes the neural network calibration method, and presents the transient temperature patterns of bubbly flow.
배대석(Dae Seok Bae),김정수(Jeong Soo Kim) 한국추진공학회 2011 한국추진공학회지 Vol.15 No.4
Numerical simulation has been performed to investigate the bubbly flow in the liquid with vertical temperature gradient. The objective of this study is to establish an accurate numerical prediction program of gas-liquid two-phase flows in a vertical temperature gradient condition, whose mathematical model is formulated by the Eulerian-Lagrangian model. The present numerical results reveal the temperature mixing mechanism and the fluid dynamical characteristics induced by the bubbly flow in the liquid with stratified temperature. The effects of bubble radius, void fraction, and gas flow rate on bubble-driven convective flow are considered, too.
과대팽창이 발생하는 초음속노즐의 충격파 구조와 추력성능에 대한 수치적 연구
배대석(Dae Seok Bae),최현아(Hyun Ah Choi),감호동(Ho Dong Kam),김정수(Jeong Soo Kim) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.4
Overexpanded flow of an axisymmetric thruster nozzle is numerically simulated to investigate effects of nozzle pressure ratio (NPR) on the shock structure and thrust performance. The Reynolds-averaged Navier-Stokes equations with k- SST turbulence model are solved utilizing FLUENT solver. As the NPR is raised, thrust performance monotonically increases with the shock structure and flow-separation point being pushed toward the nozzle exit. It is also discussed that the flow structure at nozzle-exit plane which is immediately affected by a position of nozzle-interior shocks and expansion waves, has strong influence upon the thrust performance of thruster nozzle.
정상초음파의 교란을 받는 메탄 - 공기 예혼합화염의 전파특성에 대한 초음파 구동 주파수의 영향
배대석(Dae Seok Bae),서항석(Hang Seok Seo),김정수(Jeong Soo Kim) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.2
정상초음파장의 구동 주파수가 메탄-공기 예혼합화염의 전파특성에 미치는 영향을 규명하고자 하는 실험결과를 제시한다. 고속카메라를 이용하여 화염의 전파영상을 획득하였으며, 영상 후처리를 통해 화염선단의 구조와 속도변이를 포함하는 화염의 거시적 거동을 상세히 관찰하였다. 정상초음파가 연소 반응을 촉진시켜 화염 전파속도의 증대와 화염선단 구조의 변이를 유발한다는 사실에 더하여, 초음파 구동 주파수와 당량비에 대한 화염거동의 종속성을 확인하였다. An experimental study was conducted to scrutinize the influence of the frequency of an ultrasonic standing wave on the variation in the behavior of a methane-air premixed flame. The evolutionary features of the propagating flame were captured by a high-speed camera, and the macroscopic flame behavior, including the flame structure and local velocities, was investigated in detail using a post-processing analysis of the high-speed images. It was found that a structural variation and propagation-velocity augmentation of the methane-air premixed flame were caused by the intervention of the ultrasonic standing wave, which enhanced the combustion reaction. Conclusive evidence for the dependency of the flame behaviors on the driving frequency of the ultrasonic standing wave and equivalence ratio of the reactants is presented.