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최중근(Junggeun Choi),성재용(Jaeyong Sung),이명호(Moung-Ho Lee) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.6
Velocity profiles inside a partially filled pipline have been investigated experimentally. To measure the velocity fields, a particle image velocimetry (PIV), which is a recent quantitative visualization technique, is applied. The velocity profile inside a circular pipe is well known, but if the pipe is partially filled, the problem is entirely different in the sense that the velocity distribution is significantly affected by the slope of pipe and filled water level, and so on. In order to calculate exact flow rate in the open channel or partially filled pipeline, three-dimensional velocity distributions at a given cross-sectional area are measured and compared the flow rates with the previously known empirical formula of Manning equation. The results show that the velocity profiles at center plane is considerably different from each other when the slope and water level change. Thus, The three-dimensional velocity profile can be the most plausible estimate for the exact flow rate.
표준 영상에 의한 FFT 기반 상호상관 PIV 알고리즘의 불확도 해석
이석종(Sukjong Lee),최중근(Junggeun Choi),성재용(Jaeyoung Sung),황태규(Tae Gyu Hwang),도덕희(Deog Hee Doh) 한국가시화정보학회 2005 한국가시화정보학회지 Vol.3 No.2
Uncertainty introduced by a cross-correlation algorithm based on FFT has been investigated using PIV standard images. The standard images were generated by the Monte Carlo simulation method. Both bias and random errors from the velocity vector have been analyzed with regard to the particle diameter, displacement, and the number of particles. The uncertainty of velocity is evaluated based upon the ISO/IEC standard. As a result, a total error of 0.26% is included in the PIV cross-correlation algorithm. In addition, the uncertainty budget is presented, where the effect of the above three variables is examined. According to the budget, the variation of the number of particles within the interrogation window mainly contributes to the combined standard uncertainty of the real measured velocity field when excluding the effect of errors by the experiments itself. Finally, the expanded uncertainty is found to be about 12% at the 95% confidence level.
최중근,김정배,서정원,이명호 서울산업대학교 2005 논문집 Vol.54 No.1
Characteristics of discharge pressure ripples in vane compressor has been investigated experimentally under the various circumstances, and relations between pressure rise waveform and pressure ripple waveform has been analysed. Discharge pressure ripples in compression chamber of vane compressor produced for this experiments have been measured in case of different average discharge pressure as 3, 5, 7bar and also in case of different rotor rotational velocity as 735, 1060, 1750rpm. It has been observed that the magnitude of discharge pressure ripple has tendency to increase with lower average discharge pressure, and also tendency to increase with higher rotation speed of rotor. Under the condition of constant rotation velocity of rotor and variation of average discharge pressure, start and termination rotation angles of pressure rising process have been constant without concerning variation of average discharge pressure, and gradient of pressure rising with variation of average discharge pressure has been different tendency.