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최장운(J.W.Choi),조대환(D.H.Cho),김춘식(C.S.Kim),이영호(Y.H.Lee) 한국해양대학교 해사산업연구소 1993 海事産業硏究所論文集 Vol.3 No.-
The present study is aimed to develop a new experimental method to measure velocity components in flow field by image processing technique called Particle Image Velocimetry(PIV). Here is represented a novel particle identifying algorithm by correlating two consecutive frames. And it is compared with four-frame identifying method. resulting in higher processing speed and more effective acquisition of the same particle pairs. The image processing system consists of one commercial image board slit into a personal computer and 2-dimensional sheet light generator and flow picture recording apparatus. Particle labelling, calculation of gravity centers. boundary detection and related techniques are also scrutinized and distribution of interpolated velocity vectors. equi-baric contours are also illustrated as examples.
서민식(M.S. Seo),최장운(J.W. Choi),이영호(Y.H. Lee) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
The present study is aimed to investigate flow characteristics of confined jet flow within circular pipe. Numericai method based upon revised SOLA scheme which secures conservation form of convective terms on irregular grids by interpolating the variables appearing in staggered meshes is adopted on cylindrical coordinate formation. Computation was carried out for two kinds of Reynolds number, 10^5 and 1.5 x 10^5 defined by diameter of outer pipe and time-mean driving jet velocity. Results show that periodic vortex shedding from the jet mixing layer is profound and related unsteady flow characteristics prevail over the entire region. Spatial distribution of pressure and kinetic energy, fluctuation of static wall pressure, together with radial velocity components are examined in terms of instantaneous and time-mean point of views.
김용한(Y. H. Kim),양희원(H. W. Yang),최장운(J. Y. Choi),석복렬(B. Y. Seok),이경훈(K. H. Lee),허종성(J. S. Hur) 대한전기학회 2013 대한전기학회 학술대회 논문집 Vol.2013 No.10
수도권 부하의 지속적인 증가로 차단기의 정격차단용량을 초과하는 변전소가 늘어나고 있으며, 이러한 문제를 해소하기 위해서는 차단기의 고장차단용량을 증대시켜야 하나 많은 교체 비용이 소요된다. 그러므로, 한류리액터를 설치하여 고장전류의 최대치를 감소시키는 방법이 활발하게 적용되고 있으나, 대부분 수입에 의존하고 있는 실정이다. 본 연구에서는 건식 한류리액터 개발에 필수적인 절연 및 냉각 설계기술을 분석하고 건식 한류리액터 설계기법 및 제작공정 등을 정립하였다. 또한 도출된 345kV급 건식 한류리액터의 설계안을 적용한 prototype을 제작하였으며, 국제규격에 의거한 시험을 통하여 확보된 설계기술을 검증하였다.
이영호,최장운,도덕희,Lee, Y.H.,Choi, J.W.,Doh, D.H. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.4
The present numerical study is aimed to investigate time-dependent characteristics of a two-dimensional lid-driven square cavity flow of three high Reynolds numbers, $7.5{\times}10^3$, $10^4$ and $3{\times}10^4$. A conservative convection term on irregular grids was adopted by renewing the MAC type difference schemes on regular grids. Relaxation of velocity and pressure is implemented by SOLA algorithm. In case of $Re=7.5{\times}10^3$, flow behavior converges to steady state after a transient period. But for $Re=10^4$, periodic unsteady sinusoidal fluctuation of local velocity and kinetic energy is found and continuous movements of small eddies in the secondary flow regions are also discovered. Random generation of eddies and their active migrating behavior are detected for $Re=3{\times}10^4$, resulting in complete unsteady and non-linear flow characteristics. And, an organized structure similar to a Moffat vortex is also observed from the time-mean flow patterns. Furthermore, a typoon-like vortex(TLV) appears intemittently and rotates along the separation regions and boundary layers.