• Title/Summary/Keyword: PIV measurements

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Simultaneous Measurements of Velocity Fields at Two Vertically Crossing Planes by PIV Systems Using Polarization Technique (편광기법을 이용한 수직교차평면의 PIV 속도장 동시측정)

  • Kwon S. H.;Yoon S. Y,;Kim K. C.
    • Journal of the Korean Society of Visualization
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    • v.2 no.1
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    • pp.32-38
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    • 2004
  • A new PIV technique was developed for decreasing optical error which was created during simultaneous measurements of velocity fields at a wall-normal plane and wall-parallel plane by a plane PIV and a Stereo-PIV systems. For experimental study, two different Reynolds number based on momentum thickness, Re$_{ =514 and 934 were generated in a blowing type wind tunnel under the condition of zero pressure gradient. The two Nd:Yag laser systems and three CCD cameras were synchronized. to obtain instantaneous velocity fields at the same time. To avoid optical noise at the crossing line by the two laser light sheets, a new optical arrangement using polarization was applied. The obtained velocity fields show the existence of hairpin packet structure vividly and the idealized hairpin vortex signature is confirmed by experiment.

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Visualization of Vortex Flow around Coolant Outlets Using PIV and LDV (PIV와 LDV를 이용한 냉각수 토출구 주위의 와류 가시화 연구)

  • Hong, Ji-Woo;Shin, Su-Yong;Ahn, Byoung-Kwon
    • Journal of the Korean Society of Visualization
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    • v.19 no.3
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    • pp.136-142
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    • 2021
  • Submerged and semi-submerged vehicles expel cooling water through an outlet. In this process, induced noise and vibration by the flow around the outlet have been reported, and it may cause problems directly related to survivability of the navy vessels. The coolant outlet has a net-type structure and circular columns are mostly used. In this study, flow measurements using PIV and LDV were performed for different type outlets; conventional (flat plate with round bar) and improved (flat and flat plate) configurations. Experiments were conducted at a cavitation tunnel where pressure and steady flow rate conditions are ensured for sufficient time to measure the flow. The average velocity field of the outlets were measured and compared through LDV measurements, and instantaneous vorticities were evaluated through PIV measurements. The results show that the improved type of the outlet is advantageous in terms of flow stability compared to the conventional type of the outlet.

Adaptive Stereoscopic-PIV System for the Analyses of the Flow-Structure-Interactions (FSI) of Air-Lifted Bodies (공기부양 물체의 유동-구조 연동운동 해석을 위한 능동형 스테레오-PIV 시스템)

  • Doh, Deog-Hee;Hwang, Tae-Gyu;Jo, Hyo-Je;Tanaka, Kenji;Takei, Masahiro
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2006.11a
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    • pp.420-425
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    • 2006
  • Measurements results of flow-structure-interactions (FSI) of an air-lifted body are introduced. An adaptive stereoscopic-PIV system has been constructed for the measurements of the air-lifted body. The measurement system consists of two cameras and optical sensors. The flow characteristics around a lifted cylinder body(length=60mmm, diameter =10mm, polystyrene) in the swirling flow field in a vertical pipe (length=600mm, inner diameter=) are investigated by the use of the constructed adaptive stereoscopic-PIV system. The images of the two cameras were used for the analysis of the flow fields around the floated cylinder body. The images of the cylinder body captured by the two cameras were used for the analyses of its motions. Four optical sensors (LED) were used for the detection of the postures of the freely-lifted cylinder body. The FSI analyses have been carried out to find the physical conditions at which the floating body is stabilized with its upright postures.

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Particle Image Velocimetry Measurements in Nasal Airflow (코 내부 유동의 PIV 해석)

  • Kim, Sung-Kyun;Son, Young-Rak
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.566-569
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    • 2001
  • Researchers have invectigated nasal flow both numerically and experimentally for centuries. Experimental studies most have suffered from various limitations necessary to allow the measurements to be obtained with available equipment. Nasal airflow can be subdivided into two interrelated categories; nasal airflow resistance and heat and mass transfer between the air stream and the walls of the nasal cavity. In this study, thanks to a new method for model casting by a combination of Rapid prototyping and Solidification of clear silicone, a transparent rectangular box containing the complex nasal cavity is made for PIV experiments. The CBC PIV algorithm is used for analysis.

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Visualization of Turbulent Flow around a Sphere (구 주위 난류유동에 관한 가시화 연구)

  • Jang, Young-Il;Lee, Sang-Joon
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.401-402
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    • 2006
  • The turbulent flow around a sphere was investigated using two experimental techniques: smoke-wire flow visualization in wind tunnel at Re=5300, 11000 and PIV measurements in a circulating water channel. The smoke-wire visualization shows flow separation points near an azimuthal angle of $90^{\circ}$, recirculating flow, transition from laminar to turbulent shear layer, evolving vortex roll-up and fully turbulent eddies in the sphere wake. The mean velocity field measured using a PIV technique in x-y center plane demonstrates the detailed near-wake structure such as nearly symmetric recirculation region, two toroidal vortices, laminar separation, transition and turbulent eddies. The PIV measurements of turbulent wake in y-z planes show that a recirculating vortex pair dominates the near-wake region.

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PIV Measurements of Three-Dimensional Wake Around a Road Vehicle (자동차 후류에 대한 3차원 유동의 PIV 측정)

  • Kim Jinseok;Kim Sungcho;Sung Jaeyong;Kim Jeongsoo;Choi Jongwook
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.1-4
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    • 2004
  • The PIV measurements are performed to get the quantitative flow visualization around a road vehicle. The model scaled with 1/48 is located in the middle test section of the closed-loop water tunnel and the measuring system consists of CCD camera, diode laser, synchronizer, and computer. The experimental data are obtained at two Reynolds numbers of 50,000 and 100,000 based on the model length. The quasi-three-dimensional isovorticity surfaces, based on two-dimensional velocity field data, are generated. There is little difference between the results in part of the recirculation region and the vorticity contour according to the Reynolds number. Also a little bit complicated three dimensional flows are predicted behind the road vehicle.

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Simultaneous PIV/OH PLIF Measurements in Hydrogen Nonpremixed Flames with Coaxial Air (PIV/OH PLIF 동시 측정을 이용한 동축공기 수소확산화염의 실험적 연구)

  • Kim, Mun-Ki;Kim, Seung-Han;Yoon, Young-Bin
    • 한국연소학회:학술대회논문집
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    • 2003.12a
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    • pp.115-123
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    • 2003
  • Simultaneous measurements of velocity and OH distribution were made using particle image velocimetry(PIV) and planar laser-induced fluorescence(PLIF) of OH radical in turbulent hydrogen nonpremixed flames with coaxial air. The OH radical was used as an approximate indicator of chemical reaction zone. The OH layer was correlated well with the stoichiometric velocity, $U_s$, instantaneously and on average. In addition, high strain-rate regions almost coincide with the OH distribution. The residence time in flame surface, calculated from the root-mean-square value of the radial velocity, is proportional to $(x/d_F)^{0.7}$. It is found that the mean value of principal strain rate on the OH layer can be scaled with $(x/d_F)^{-0.7}$ and therefore, the product of the residence time and the mean strain rate remains constant over all axial positions.

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Measurements of a Ship's Propeller Wake with Stereoscopic-PIV and Stereoscopic-PTV (스테레오 PTV와 스테레오 PIV에 의한 선박프로펠러 후류측정)

  • Doh, Deog-Hee;Hwang, Tae-Gyu;Lee, Sang-Joon
    • Journal of the Korean Society of Visualization
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    • v.5 no.2
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    • pp.26-32
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    • 2007
  • Stereoscopic PTV and Stereoscopic-PIV measurements have been carried out for the studies of the wake of a ship's propeller. Stereoscopic photogrammetry based on a 3D-PTV principle was introduced using two high-definition cameras(1k x 1k, 30Hz). The arrangement of the two cameras was based on angular position. The pair-matching of the three-dimensional velocity vectors were based on Genetic Algorithm based 3D-PTV technique. The results obtained by both measurement systems have been compared at the advance ratio J=0.88(290 rpm, d=54 mm). Turbulent properties have also been compared each other at the same condition.

Non-Invasive Measurement of Shear Rates of Pulsating Pipe Flow Using Echo PIV (에코 PIV를 이용한 맥동 유동에서의 in vitro 전단률 측정 연구)

  • Kim, Hyoung-Bum;Chung, In-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.12
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    • pp.1567-1572
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    • 2004
  • Although accurate measurement of velocity profiles, multiple velocity vectors, and shear stress in arteries is important, there is still no easy method to obtain such information in vivo. This study shows the utility of combining ultrasound contrast imaging with particle image velocimetry (PIV) for non-invasive measurement of velocity vectors. The steady flow analytical solution and optical PIV measurements (for pulsatile flow) were used for comparison. When compared to the analytical solution, both echo PIV and optical PIV resolved the steady velocity profile well. Error in shear rate as measured by echo PIV (8%) was comparable to the error of optical PIV (6.5%). In pulsatile flow, echo PIV velocity profiles agreed well with optical PIV profiles. Echo PIV followed the general profile of pulsatile shear stress across the artery but underestimated wall shear at certain time points. These studies indicate that echo PIV is a promising technique for the non-invasive measurement of velocity profiles and shear stress.