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한라산 주변에 발생하는 Karman Vortex Street 재현
권지혁(Kwon Ji-hyuk·Lee),이연원(Lee Yeon-won),김영덕(Kim Young-duk),박광열(Park Kwang-yul) 한국풍공학회 2006 한국풍공학회지 Vol.10 No.1
늦가을과 초본 사이 제주도 후면에 Karman vortex street가 발생한다. 이러한 vortex가 발생하기 위해서는 기온 역전층과 5 ~ 13 m/s의 지속적인 바람이 필요하다는 것을 밝히기 위한 많은 연구들이 있었다. 이러한 vortex clouds는 발생 후 주 풍향의 방향을 이동하게 된다. Karman vortex street는 기상학에서 매우 흥미로운 주제이다. 본 연구에서는 LES 난류 모델을 이용하여 Karman vortex street에 관한 해석을 수행하고 수치해석을 통해 얻은 결과와 기상 데이터가 일치함을 보였다. From late autumn to the beginning of the spring, the phenomena of the Karman vortex street have been frequently observed in the wake of Mt. Halla in the Jeju island. Some researches revealed that the necessary conditions for development of these vortex clouds are a strong low-level inversion of temperature and a persistent wind speed of 5 to 13m/s. After the cloud is formed, the vortex clouds are shed from alternating sides of Jeju island and then move downwind with main airflow stream. The Karman vortex street in the wake of the Jeju island was one of the interesting topics in meteorology. In this study, CFD using LES turbulence model was developed to investigate the Karman vortex street and the results of CFD showed a good agreement with weather data.
선상가열시 이동열원 조건에 따른 가열 판재의 온도분포에 관한 연구
최윤환,이연원,최광,Choi, Yoon-Hwan,Lee, Yeon-Won,Choi, Kwang 한국마린엔지니어링학회 2010 한국마린엔지니어링학회지 Vol.34 No.5
Line heating is a manufacture method, which was widely used to machining a curved surface in the ship construction. The qualities using by line heating are very difference compare to the proficiency level of the engineer. So it's mainly depend on the automation equipment instead of the proficiency level engineer. In this study, it would be investigate the temperature distribution of the heating plate, which was used by the automation equipment according to line heating. The main factors are the moving velocity of the heating source, strength and the heating method separately, in temperature distribution while line heating. In this paper, it was investigated the temperature change with the vary of each three variables. The numerical result showed that peak temperature decrease if the moving velocity of the heating source increased. It can also calculate the change quantitatively that the peak temperature and temperature distribution changed linearly with the vary of the heating source. 선박 건조공정에서 외피의 곡면 가공에 많이 사용하는 가공법을 선상가열법이라고 한다. 선상가열법은 엔지니어의 숙련도에 따라 품질의 차이가 커지기 때문에 현재에는 엔지니어의 숙련도에 의존하지 않는 자동화기기를 사용하여 선상가열을 수행하는 경우가 많다. 본 연구에서는 자동화기기를 사용한 선상가열에 의한 가열판재의 온도분포를 조사하고자 한다. 선상가열시 적용되는 주요한 변수는 가열원의 이동속도, 강도 및 가열 방식 등이 있으며, 본 연구에서는 세 가지 변수를 중심으로 가열판재의 표면 및 내부온도가 어떻게 변화하는지를 조사하였다. 해석결과 가열원의 이동속도가 빨라질수록 판재의 피크온도는 낮게 형성되는 것을 확인하였고, 또한 열원의 크기에 따른 피크온도 및 온도분포가 선형적으로 변화하는 것을 정량적으로 계산할 수 있었다.
이종훈(Jong-Hoon Lee),이연원(Yeon-Won Lee),김재환(Jae-Hwan Kim) 한국마린엔지니어링학회 2005 한국마린엔지니어링학회 학술대회 논문집 Vol.2005 No.-
As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.