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레이저형광여기(LIF)를 이용한 비등온 제트유동의 온도장 측정
윤정환,이상준,Yoon, Jong-Hwan,Lee, Sang-Joon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.10
A 2-dimensional temperature field measurement technique using PLIF (Planar Laser Induced Fluorescence) was developed and it was applied to an axisymmetric buoyant jet. Rhodamine B was used as a fluorescent dye. Laser light sheet illuminated a two-dimensional cross section of the jet. The intensity variations of LIF signal from Rhodamine B molecules scattered by the laser light were captured with an optical filter and a CCD camera. The spatial variations of temperature field of buoyant jet were derived using the calibration data between the LIF signal and real temperature. The measured results show that the turbulent jet is more efficient in mixing compared to the transition and laminar jet flows. As the initial flow condition varies from laminar to turbulent flow, the entrainment from ambient fluid increases and temperature decay along the jet center axis becomes larger. In addition to the mean temperature field, the spatial distributions of temperature fluctuations were measured by the PLIF technique and the result shows the shear layer development from the jet nozzle exit.
윤정환(Jong-Hwan Yoon) 한국가시화정보학회 2021 한국가시화정보학회지 Vol.19 No.2
It is essential to accurately predict the change in water level, velocity, and flow rate for each passage of the grit chamber according to the operating conditions of the pump. In this study, VOF multiphase flow analysis was performed, and the flow characteristics of the grit chamber were predicted. As a result of simulations, the sedimentation phenomenon after the entrance of the grit chamber channel is expected to occur on the side walls. When 6 channels are used, the average speed of the channels is about 52% of the design standard, and when 4 channels are used, the value increases to 74% of the design standard. The average water level in the channels tends to decrease as the flow velocity increases, and the water level in the absorption well with a larger flow rate is maintained lower than that in the absorption well with a smaller flow rate.
윤정환(Jong-Hwan Yoon),백승조(Seung-Jo Baek),김형범(Hyung-Bum Kim),이상준(Sang-Joon Lee),김기원(Ki-Weon Kim) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
The variations of temperature field in a passenger compartment were measured by using a HSI true color image processing system and TLC (Thermochromic Liquid Crystal) solution. Under the same condition, the velocity field variations were measured by using a 2-frame PTV technique. This 2-frame PTV uses the concept of match-probability to track true velocity vectors from two consecutive image frames. The temperature field and velocity field in the passenger compartment were affected significantly by the ventilation mode. The panel-vent mode heating had shorter elapse time to reach a uniform temperature than the foot-vent mode under the same ventilation condition. The temperature nonuniformity inside the passenger compartment could be minimized effectively by using the bi-level heating mode. The temperature increase rate in the rear passenger compartment was lower than the front compartment, especially in the vicinity of the rear seat occupants' knee level.<br/> <br/>
윤정환(Jong-Hwan Yoon) 한국가시화정보학회 2010 한국가시화정보학회지 Vol.7 No.2
In this study, we optimized the shape of the surface aerator that will be installed in a biological reactor using the response surface method. Response surfaces of mass flow rate, impeller torque, mass flow rate per impeller torque are generated and used to track the optimum shape of the aerator. MOGA(Multi-Objective Genetic Algorithm)method is adopted to find the optimum results. By increasing the mass flow rate per impeller torque, increase of oxygen supply efficiency to a reactor is anticipated. To verify the usability of the surface aerator, PIV measurements onflow fields inside a scale-downed biological reactor model are carried out.
Stereoscopic PTV 기법의 개발 및 정확도 검증
윤정환(Jong-Hwan Yoon) 한국자동차공학회 2004 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
A novel stereoscopic particle tracking velocimetry (SPTV) velocity field measurement technique based on the 2frame hybrid PTV method is presented. The expansion of 2D PTV to stereoscopic PTV is facilitated by the fact that the PTV method tracks individual particle centroids. The data processing routine and measurement uncertainty of the SPTV technique are compared with those of conventional stereoscopic PIV (SPIV). In addition, the centroid translation effect of 2D PlV and its effect on SPIV measurements are discussed. To evaluate the performance and measurement accuracy of the developed SPTV technique, it was applied to flow images of rigid body motion and synthetic standard images of jet shear flow and impinging jet flow. Compared to the SPIV method, the SPTV technique has inherited merits of concise and precise velocity evaluation procedures and provides better spatial resolution and measurement accuracy.
윤정환(Jong-Hwan Yoon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.10
A stereoscopic particle tracking velocimetry(SPTV) technique based on the 2-frame hybrid particle tracking velocimetry (PTV) method was developed. The expansion of 2D PTV to SPTV is facilitated by the fact that the PTV method tracks individual particle centroids. To evaluate the performance and measurement accuracy of the present SPTV technique, it was applied to flow images of rigid body translation and synthetic standard images of jet shear flow and impinging jet flow. The data processing routine and measurement uncertainty of the SPTV technique are compared with those of conventional stereoscopic particle image velocimetry (SPIV). In addition, the centroid translation effect of 2D particle image velocimetry (PlV) is defined and its effect on SPIV measurements is discussed. Compared to the SPIV method, the SPTV technique has inherited merits of concise and precise velocity evaluation procedures and provides better spatial resolution and measurement accuracy.
수치해석을 이용한 순환형공기분급기 유동특성 및 분급성능 연구
윤정환(Jong-Hwan Yoon),정준교(Jun-Gyo Cheong) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.3
본 연구에서는 전산유체역학 프로그램을 이용하여 순환형공기분급기 내부유동 및 입자거동을 해석하였다. 주날개 및 분급날개의 회전속도 조건을 변화시키며 이에 따른 등급분급효율, 절단입경 및 분급첨예도 변화를 예측하였다. 주날개의 회전속도를 제어함으로써, 절단입경을 증가시킬 수 있었으나, 오염토양 분급에 적용할 수 있을 정도의 정확도를 확보할 수 없었다. 반면, 분급날개의 회전속도를 증가시킴으로써, 절단입경을 감소시킬 수 있었으며, 보다 정확하게 입자를 선별할 수 있었다. 결과적으로 주날개와 분급날개를 동시에 사용할 경우, 높은 분급첨예도 결과를 보이며, 우수한 분급특성을 유지할 수 있었다. In this study, we performed numerical simulations on a circulating air classifier using a commercial computational fluid dynamics program. The variations in the grade efficiency, the cut-size and the cut-sharpness were calculated and discussed. By controlling the rotating speed of the main fan, the cut-size could be rapidly increased. However the linearity of the cut-size variation with respect to the main fan speed was not sufficient for application to contaminated soil classification processes. On the other hand, by varying the rotating speed of the classifying fan, the cut-size gradually decreased and could be precisely adjusted. Using both the main fan and the classifying fan, we could achieve larger cut-sharpness values and better classifying performances.