• 한국자동차공학회논문집
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• 제6권4호
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• pp.219-227
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• 1998

This paper describes the fuel spray characteristics of gasoline port injectors such as the breakup procedures of liquid fuel, breakup and extinction behaviors of fuel spray at nozzle tip, time history of SMD and velocity distribution of fuel spray in the direction of fuel stream. Pintle-type gasoline fuel injector was used to analyze mentioned spray characteristics. In order to visualize the fuel spray behaviors and to measure the droplet mean diameter and velocities of spray droplets, the Schlieren method, digital image processing and auto-correlation PIV were applied in this study. In addition, the spray characteristics according to the variation of time were considered. The results of fuel spray show that the liquid sheet breakup starts at 10mm downstream actively. The flying time is approximately 4msec between 50mm and 80mm down the nozzle tip. Also, SMD of fuel spray, the number of droplets and fuel velocity distribution at each point of downstream are discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.410-416
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• 2001

An algorithm of 3-D particle image velocimetry(3D-PIV) was developed for the measurement of 3-D velocity field of complex flows. The measurement system consists of two or three CCD camera and one RGB image grabber. In this study, stereo photogrammetty was applied for the 3-D matching of tracer particles. Epipolar line was used to decect the stereo pair. 3-D CFD data was used to estimate algorithm. 3-D position data of the first frame and the second frame was used to find velocity vector. Continuity equation was applied to extract error vector. The algorithm result involved error vecotor of about 0.13 %. In Pentium III 450MHz processor, the calculation time of cross-correlation for 1500 particles needed about 1 minute.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.139-145
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• 2001

The objective of experimental study is to apply simultaneous measurement by PIV(Particle Image Velocimetry) to high_speed flow characteristics within ginseng cleaner model. Three different kinds of flow rate(15. 20, 27l/min) are selected as experimental condition. Optimized cross correlation identification to obtain velocity distribution, time-mean velocity distribution, velocity, profile, kinetic energy and turbulence intensity are represented quantitatively for the deeped understanding of the flow characteristics in a ginseng cleaner model.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.652-659
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• 1998

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.

• 연구논문집
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• 통권30호
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• pp.59-65
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• 2000

The objective of experimental study is to apply simultaneous measurement by PIV(Particle Image Velocimetry)to high_speed flow characteristics within Ginseng washing machine. Three different kinds of flow rate(15,20,27 $\ell$/min)are selected as experimental conditions. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. Instantaneous velocity distribution, time-mean velocity distribution and velocity profiles are represented quantitatively at the full-scale region for the deeper understanding of the flow characteristics in Ginseng washing machine.

• 대한기계학회논문집B
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• 제35권6호
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• pp.603-608
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• 2011

입자추적유속계(PTV)는 나노 및 바이오 분야의 유체유동장에서는 각 입자들을 추적하여 속도측정을 하는 관계로 많은 강점이 있다. 그러나 측정원리상 보간에 의한 속도장 측정오차를 피할 수 없는 관계로 PTV기술을 사용함에 있어서 제한적이었다. 본 연구에서는 어파인변환 알고리듬을 PIV 및 PTV측정에 도입함으로써 보간에 의한 오차를 줄일 수 있는 어파인변환 기반 하이브리드 PIV알고리듬을 구축하였다. 구축된 알고리듬에 대한 성능평가를 위하여 Green-Taylor와유동의 수치적 데이터를 이용한 가상영상에 대한 시험을 실시하였으며, 이로부터 입자수가 2000개 이상일 때 최적의 측정성능임을 확인하였으며 상호상관PIV법 및 확률일치PTV법보다 우수한 측정성능임을 확인하였다. 나아가 길이비 2:1($6cm\;{\times}3cm$)인 장방형 물체후류(Re=5,300)에 대한 실험영상에 대한 실제 계산을 통하여 구축된 알고리듬에 대한 측정성능의 우수성을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.704-715
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• 2005

In this study, to investigate in-cylinder tumble or swirl intake flow of a gasoline engine, the flow characteristics were examined with opening control valve (OCV) and several swirl control valves (SCV) which intensify intake flow through steady flow experiment, and also turbulent characteristics of in-cylinder flow field were investigated by 2-frame cross-correlation particle image velocimetry (PIV) method. In the investigation of intake turbulent characteristics using PIV method, the different flow characteristics were showed according to OCV or SCV figures. The OCV or SCV installed engine had higher vorticity and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder. Above all, SCV B type was superior to the others. About energy dissipation and reynolds shear stress distribution, a baseline engine had larger loss than OCV or SCV installed one because flow impinged on the cylinder wall. It should be concluded, from what has been said above, as swirl component was added to existing tumble flow adequately, it was confirmed that turbulent intensity was enlarged, flow energy was conserved effectively through the experiment. In other words, there is a suggestion that flow characteristics as these affected to in-cylinder combustion positively.

• 동력기계공학회지
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• 제4권2호
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• pp.11-16
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• 2000

Simultaneous quantitative measurements are made of the velocity fields for two-dimensional natural convection in a rectangular enclosure using PIV(Particle Image Velocimetry). The experiments are performed at a Prandtl number of 6.62, an aspect ratio of 1.0, Rayleigh numbers from $1.294{\times}10^6\;to\;3.8841{\times}10^6$, and angles of inclination of $0^{\circ},\;30^{\circ}\;and\;60^{\circ}$ inside a $30mm{\times}30mm{\times}8mm$ cavity made of an acrylic glass 10mm, with two isothermal copper walls kept at a prescribed temperature. The experimental results agreed very well with the numerical results. It was found that the flow consisted of a large double convection cell at angle of inclination of $60^{\circ}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.381-384
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• 2000

Relationships between biochemical phenomena and hemodynamics on human endothelial cells are very important to study the mechanism of atherosclerotic formation and development. The objective of this study is to investigate the flow phenomena around the endothelial cell model by the PIV experiment. The microscopic images of endothelial cells were acquired by a CCD camera to fabricate the shape of endothelial cell. The cell models were fabricated by using a photoforming process. Two consecutive particle images were captured by the CCD camera for the image processing. Conifer powder as the tracing particles was added to water to visualize the flow field. The cross-correlation method was applied fer the image processing of the flow visualization. Pressure and wall shear stress variations on the surfaces of the endothelial cells were calculated to investigate the effects of hemodynamic forces on the morphological changes.