• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2002년도 추계학술대회 논문집
• /
• pp.97-99
• /
• 2002

Turbulent premixed flames were a subject of many researches for a number of decades. Especially, Borghi suggested a manificent diagram classifying turbulent combustion reasions and Lipatnikov and Chomiak modified this diagram. But this diagram has difficulties tn defining a flame thickness and velocity and measuring integral length scales In addition, recently experimental techniques are being developed, so we can accurately use PIV diagnostics measuring 2D velocity field instead of LDV and make good use of PLIF techniques for obtaining the flame information. In this study, according to developing techniques, suggest a new diagram replacing the existing Borghi diagram. Simultaneous PIV/OH PLIF measurements are used, which measure a shear strain rate and a location of flames, respectively. The shear strain rate represents turbulence and the OH signal indicates the flame information, but there is no geometric Information which is very important to flame quenching. Hence, to consider the geometric information, calculate fractal dimensions of the OH images. So the diagram suggested in this research has three axes which consist of strain rate, OH signal, and fractal dimension and can classify turbulent premixed flames.

• 한국기계가공학회지
• /
• 제20권7호
• /
• pp.58-65
• /
• 2021

Research on general particle image velocimetry (PIV) has been conducted extensively, but studies on granular PIV are relatively insufficient. In addition, the parameters used for analyzing granular PIV need to be optimized. In this study, we analyzed the error of velocity measurements based on the interrogation area (64-192 pixel), frame per second (30-120 FPS), and video resolution [ultrahigh definition (UHD) and high definition (HD)] within the velocity range typically measured in hoppers. The estimated errors of the granular PIV were below 5%, which is generally acceptable. However, considering the data reliability, the flow velocity in the hopper could be measured with less than 5% error at 120 FPS or higher in the HD resolution and 30 FPS or higher in the UHD resolution.

• 대한기계학회논문집B
• /
• 제27권4호
• /
• pp.518-523
• /
• 2003

Airflow in the nasal cavity of Korean adults is investigated experimentally by PIV measurement. Quantitative data for normal and abnormal nasal cavities with adenoid vegetation are obtained. The CBC PIV algorithm with window offset is used for PIV flow analysis. Average and RMS distributions are obtained for inspirational and expirational nasal airflows. Comparisons between western and Korean nasal airflows are appreciated. Due to the difference in geometry of the frontal part of nasal cavity, the flow near nares shows the difference. For the joint research on nasal deceases, PIV measurements of nasal airflow for nasal cavities with 50% and 70% adenoid vegetation are conducted for the first time. Comparisons in nasal airflows for both normal and abnormal cases are also appreciated.

• 한국가시화정보학회지
• /
• 제3권1호
• /
• pp.26-35
• /
• 2005

The combination of ultrasound echo images with digital particle image velocimetry (DPIV) method has resulted in a two-dimensional, two-component velocity field measurement technique appropriate for opaque flow conditions including blood flow in clinical applications. Advanced PIV processing algorithms including an iterative scheme and window of offsetting were used to increase spatial resolution. The optimum concentration of the ultrasound contrast agent used for seeding was explored. Velocity validation tests in fully developed laminar pipe flow and pulsatile flow showed good agreement with both optical PIV measurements and the known analytic solution. These studies indicate that echo PIV is a promising technique for the non-invasive measurement of velocity profiles and shear stress.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.683-686
• /
• 2008

To diagnose vascular diseases from the viewpoint of hemodynamics, detailed quantitative hemodynamic information of related blood flows with a high spatial resolution of tens micrometer and a high temporal resolution in the order of millisecond were required. For investigating the hemodynamic phenomena of vascular circulatory diseases, a new diagnosing technique combining a medical radiography and PIV method was newly developed. This technique consisted of a medical X-ray tube, an X-ray CCD camera, a shutter module for double pulse-type X-ray source, and a synchronizer. Through several preliminary tests, the feasibility of the angiographic PIV technique was verified. For in-vivo measurements to real blood flows, we developed tracer microcapsules which were optimized to this system by encapsulating a contrast material of iodine with a matrix material of PVA (polyvinylpyrrolidone). In near future, the angiographic PIV technique would be useful for diagnosing hemodynamic phenomena of vascular diseases and for their early detection.

• 대한기계학회논문집B
• /
• 제28권12호
• /
• pp.1528-1534
• /
• 2004

The combination of ultrasound echo images with digital particle image velocimetry (DPIV) methods has resulted in a two-dimensional, two-component velocity field measurement technique appropriate for opaque flow conditions including blood flow in clinical applications. Advanced PIV processing algorithms including an iterative scheme and window offsetting were used to increase spatial resolution. The optimum concentration of the ultrasound contrast agent used for seeding was explored. Velocity validation tests in fully developed laminar pipe flow result of echo PIV showed good agreement with both optical PIV measurements and the known analytic solution based on a volume flow measurement.

• 대한조선학회논문집
• /
• 제37권3호
• /
• pp.37-44
• /
• 2000

수면 하에서 정속으로 움직이는 MACA0012 수중익에 의하여 생성되는 정상파 및 쇄파에 대한 실험적 연구를 회류수조에서 수행하였다. 실린더의 몰수깊이에 따른 자유표면 파형을 관측하였고, PIV를 이용하여 수중익과 자유표면 사이 유동장의 순간속도와 평균속도를 계측한 후 와도분포를 구하였다. 쇄파의 발생, 전개 그리고 소멸과정을 조사하였고, 특히 자유표면 부근의 와류 구조와 같은 복잡 순간유동장의 가시화를 통하여 수중익과 쇄파 간의 상호작용을 해석하고자 하였다. 본 실험으로 PIV 계측기법은 조선해양공학의 다양한 연구분야에 훌륭히 적용될 수 있음을 보았고 더욱이 정량적인 해석이 필요한 실험에도 사용이 가능함을 확인하였다.

• 대한기계학회논문집B
• /
• 제28권9호
• /
• pp.1015-1021
• /
• 2004

Micro-resolution Particle Image Velocimetry(Micro-PIV) was used to measure the flow in a micro-branch(Micro-Bypass). In this paper, effects of particle lump at the tip of a Micro-branch and difficulties of Micro-PIV measurements for microfluidics with branch passage were described. Micro-bypass was composed of a straight channel(200(100)${\mu}$m width ${\times}$ 80${\mu}$m height) and two branches which has 100(50)${\mu}$m width ${\times}$ 80${\mu}$m height. One of branches was straight and the other was curved. Experiments were performed at three regions along streamwise direction(entrance, middle and exit of branch) and five planes along vertical direction (0, ${\pm}$10, ${\pm}$20 ${\mu}$m) for the range of Re=0.24, 1.2, 2.4. Numerical simulation was done to compare with the measurements and understand the effects of particle lump at the tip of branch. And another fluid(3% poly vinyl Alcohol aqueous solution) were adapted for this study, so there were no particle sticking. In this case, we could get velocity difference between straight and curved branches.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권4호
• /
• pp.437-442
• /
• 2015

본 연구에서는 SI 엔진의 정상유동장치에서 충격식 스월미터로 측정한 스월비와 PIV(입자영상유속계) 속도장을 적분하여 구한 스월비를 비교 고찰하였다. PIV 속도장으로부터 스월비를 산출하는 방식에 있어서는 토크를 실린더의 기하학적 중심과 스월 중심에서 각각 계산하여 비교하였다. 또한, 정상유동장치에서 토크의 측정 위치를 변화하여 그에 따른 영향도 고찰하였다. 그 결과, 와류가 안정화되지 못한 상류에서는 충격식 스월미터의 측정값이 PIV로 측정한 값보다 크게 나타났다. PIV 측정에 있어서는 유동 상류에서 실린더 중심을 기준으로 산출한 값이 스월 중심으로 산출한 값보다 작게 나타났다. 측정위치가 하류로 이동하여 스월이 안정화되면서 측정방법에 따른 차이점이 줄어든다.

• 대한기계학회논문집B
• /
• 제29권11호
• /
• pp.1182-1188
• /
• 2005

An x-ray PIV (Particle Image Velocimetry) technique was developed to measure quantitative information on flows inside opaque conduits and on opaque-fluid flows. At first, the developed x-ray PIV technique was applied to flow in an opaque Teflon tube. To acquire x-ray images suitable for PIV velocity field measurements, refraction-based edge enhancement mechanism was employed using detectable tracer particles. The optimal distance between with the sample and detector was experimentally determined. The resulting amassed velocity field data were in reasonable agreement with the theoretical prediction. The x-ray PIV technique was also applied to blood flow in a microchannel. The flow pattern of blood was visualifed by enhancing the diffraction/interference -bas ed characteristic s of blood cells on synchrotron x-rays without any contrast agent or tracer particles. That is, the flow-pattern image of blood was achieved by optimizing the sample (blood) to detector distance and the sample thickness. Quantitative velocity field information was obtained by applying PIV algorithm to the enhanced x-ray flow images. The measured velocity field data show a typical flow structure of flow in a macro-scale channel.