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최장운,조대한,최민선,이영호 한국마린엔지니어링학회 1996 한국마린엔지니어링학회지 Vol.20 No.4
To maintain high spacial accuracy and rapid CPU time in interpolating data from grid to random position or inversely in PIV, proposed many technuques are compared and discussed mainly in terms of interpolating error and computing time. And artificial PIV atmosphere data is furnished by CFD result. First, for interpolation from grid to random position, multiquadric method gives the highest accuracy with the longest CPU time and Taylor series expansion methods give reasonable accuracy with less calculating load. Secondly, the sub-pixel resolution analysis in estimating the coordinates of the maximum correlation coefficients essential in the grey level correlation PIV reveal that 8-neighbours 2nd-order least square interpolation gives utmost accuracy in terms of the real flow conditions.
최장운,남구만,이영호,김미영,Choi, Jang-Woon,Nam, Koo-Man,Lee, Young-Ho,Kim, Mi-Young 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.6
A Process of 3-D Particle image velocimetry, called here, as '3-D volume PIV' was developed for the full-field measurement of 3-D complex flows. The present method includes the coordinate transformation from image to camera, calibration of camera by a calibrator based on the collinear equation, stereo matching of particles by the approximation of the epipolar lines, accurate calculation of 3-D particle positions, identification of velocity vectors by 3-D cross-correlation equation, removal of error vectors by a statistical method followed by a continuity equation criterior, and finally 3-D animation as the post processing. In principle, as two frame images only are necessary for the single instantaneous analysis 3-D flow field, more effective vectors are obtainable contrary to the previous multi-frame vector algorithm. An Experimental system was also used for the application of the proposed method. Three analog CCD camera and a Halogen lamp illumination were adopted to capture the wake flow behind a bluff obstacle. Among 200 effective particle s in two consecutive frames, 170 vectors were obtained averagely in the present study.
최장운 한국마린엔지니어링학회 1998 한국마린엔지니어링학회지 Vol.22 No.5
The present study is aimed to develop a new PIV operating software through optimization of vector tracking identification including versatile pre-processings and post-processing techniques. And the result exhibits an improved version corresponding various input and output multimedia compared to previous commercial software developed by other makers. An upgraded identification method called grey-level cross correlation coefficient method by direct calculation is suggested and related user-friendly pop-up menu are also represented. Post-processings comprising turbulence statistics are also introduced with graphic output functions.
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.
발전기 냉각성능 향상을 위한 통풍 유로 형상 변수에 관한 수치해석 연구
최장운(Jangun Choi),김완기(Wangi Kim),전무종(Moojong Jeon),류순기(Soongi Ryu) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
To develop high efficiency and lightweight generator, cooling system is needed considering internal heat loss. The flow network of single ended ventilation and IC01 type cooling system is comprised of radial ducts in lamination, gap between frame and stator, bypass, backward-curved fan, etc. The flow rate for cooling is determined by hydraulic loss of each airflow branch. The increasing hydraulic loss by saving weight of frame reduces flow rate and induces temperature rise in the winding. Consequently, generator efficiency and durability of insulation decreases. In this study, major geometric parameters of airflow passage are selected for cooling improvement as analyzing distribution of temperature rise and flow rate by CFD.