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Stereoscopic PIV 기법의 개발과 이를 이용한 축류 홴 후류의 유동해석
윤정환,이상준,Yun, Jeong-Hwan,Lee, Sang-Jun 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.2
A stereoscopic PIV (SPIV) measurement system based on the translation configuration was developed and applied to the flow behind a forward-swept axial-fan. Measurement of three orthogonal velocity components is essential for flow analysis of three-dimensional flows such as flow around a fan or propeller. In this study, the translation configuration was adopted to calculate the out-of-plane velocity component from 2-D PIV data obtained from two CCD cameras. The error caused by the out-of-plane motion was estimated by direct comparison of the 2-D PIV and 3-D SPIV results that measured from the particle images captured simultaneously. The comparison shows that the error ratio is relatively high in the region of higher out-of-plane motion near the axial fan blade. The turbulence intensity measured by the 2-D PIV method is bigger by about 5.8% in maximum compared with that of the 3-D SPIV method. The phase-averaged velocity field results show that the wake behind an axial fan has a periodic flow structure with respect to the blade phase and the characteristic flow structure is shifted downstream in the next phase.
유한요소격자에 기초한 일반적인 금형면 묘사와 3차원 박판성형공정에의 응용
윤정환,김종봉,양동열,김석관,유동진,이재진,Yun, Jeong-Hwan,Kim, Jong-Bong,Yang, Dong-Yeol,Kim, Seok-Gwan,Yu, Dong-Jin,Lee, Jae-Jin 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.3
One of the most important factor to be considered for the analysis of sheet metal forming processes is the tool surface description for arbitrarily- shaped sheet metal parts. In the present study , finite element approach is used to describe the arbitrarily shaped tool surface. In finite element mesh approach, tool surfaces ar, described by finite elements. The finite elements mesh description of the tool surface, which is originally described by CAD data, needs much time and time-consuming graphic operation. The method, however, has been widely used to describe a complex tool surface. In the present study, the contact searching algorithm for the finite element mesh approach is developed based on cell strategy method and sheet surface normal scheme. For the verification purpose, a clover cup drawing, Baden-Baden oilpan problem and a trunk floor drawing were investigated. The computational results based on the finite element approach were compared with the results of available parametric patch approach and experiments.
TLC와 컬러화상처리를 이용한 Hele-Shaw Cell 내부 대류 온도장 측정
윤정환,도덕희,이상준,Yun, Jeong-Hwan,Do, Deok-Hui,Lee, Sang-Jun 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.3
Variation of temperature field in a Hele-Shaw convection cell was measured by using a HSI true color image processing system and TLC(Thermochromic Liquid Crystal) solution. The relationship between the hue value of TLC color image and real temperature was obtained and this calibration result was used to measure the true temperature. The temperature field in the Hele-Shaw convection cell shows periodic characteristics of 45 sec at Ra = 9.3 * 10$\^$6/. The temperature field measurement technique developed in this study was proved to be a useful and powerful tool for analyzing the unsteady thermal fluid flows.
윤정환 ( Yun Jeong Hwan ) 미래군사학회 2019 한국군사학논총 Vol.8 No.1
The purpose of this paper is to identify the problems of regional defense operations units and to suggest a method of regional defense operations considering the posterior regional operations environment. In summary, First, the units for regional defense operations are divided into active units and reserve forces. Eventually, active forces are also organized as reserve forces, which is expected to limit the use of combat power. Therefore, it should be improved to maintain a high level of combat power by improving the percentage of full army units. The mission should clearly distinguish between active and reserve forces. Second, it is necessary to change the concept of regional defense operations, which is to carry out civilian, military, and military combat operations in units of battalions. The civil defense, military, and military combat operations should be planned by the local defense division, To this end, it is necessary to coordinate the formation of the solidarity and to organize the entire battalion and one city, county, and district. Third, the Unified Defense Support Headquarters operated by Eup, Myeon, and Dong should be integrated into city, county, and county. Fourth, in order to overcome the difficulties of the commander of the regional defense operation unit, it is necessary to remove the basis of the budget for the upbringing support of the local governments specified in the reserve army establishment law and reflect the budget for the reserve army in the defense budget.