• Title/Summary/Keyword: PIV

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Analysis of Airflows in a Room with Panoramic PIV (파노라마-PIV를 이용한 실내기류 해석)

  • Hwang Tae-Gyu;Doh Deog-Hee
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.12
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    • pp.1154-1160
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    • 2005
  • A panoramic-PIV system has been constructed for the analysis of the airflows in a room. Smoke is used as seeding particles and are visualized by a pulsed laser (Nd-Yag, 120 mJ). Panoramic images have been obtained by an image composition process using the two images obtained by the two cameras $(1k\times1k)$ that are viewing the wide measurement areas. Velocity vector fields have been obtained by the grey-level cross-correlation PIV method. Three room models $(L{\times}W{\times}H[mm^3],\;500\times500\times250,\;350\times350\times175,\;250\times250\times125)$ have been tested. The experimental results have proven that the constructed panoramic-PIV system can be used as a useful tool for analyzing the airflow characteristics in the room models.

Development of Echo PIV Using Ultrasound Contrast Agent (초음파 조영제를 애용한 Echo PIV 기법의 개발)

  • Kim, Hyoung-Bum
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.12
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    • pp.1528-1534
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    • 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.

Flow Survey around Two-Dimensional Circular Cylinder using PIV Technique (PIV를 사용한 2차원 원형 실린더 주위의 유동해석)

  • 박건선;곽영기
    • Journal of Ocean Engineering and Technology
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    • v.18 no.3
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    • pp.1-7
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    • 2004
  • Flaw visualization and velocity field measurement methods have practical applications in the various fluid engineering fields, such as mechanics, ships, and heat fluids. In this study, the basic principles and theoretical methods are used to establish an application technique of Particle Imae Velocimetry(abbreviated to PIV below). Accordingly, the measured results of velocity field distribution of a section inside the Circulating Water Channel (abbreviated to CWC below) are computed using the PIV is presented. The uniformity of velocity distribution of the section in CWC is confirmed, by comparing this PIV data with the existing current meter data. Also, in order to measure the flaw fields of surroundings of 2-dimensional cylinder in the CWC, the flaw visualization technique using the PIV is applied.

Echo-PIV: in vivo Flow Measurement Technique (에코 PIV: in vivo 유동 측정기법)

  • kim Hyoung-Bum;Hertzberg Jean;Shandas Robin
    • Journal of the Korean Society of Visualization
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    • v.3 no.1
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    • pp.26-35
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    • 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.

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Development of a Dynamic PIV System for Turbulent Flow Analysis (난류유동 해석을 위한 Dynamic PIV 시스템의 개발)

  • Lee Sang-Joon;Jang Young-Gil;Kim Seok
    • Journal of the Korean Society of Visualization
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    • v.3 no.1
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    • pp.71-77
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    • 2005
  • Information on temporal evolution of whole velocity fields are essential for physical understanding of a complicated turbulent flow. Due to advances of high-speed imaging technique, laser and electronics, high-speed digital cameras and high-repetition pulse lasers are commercially available in nowadays. A dynamic PIV system that can measure consecutive instantaneous velocity field with 1K$\times$ 1K pixels resolution at 1 fps was developed. It consists of a high-speed CMOS camera and a high-repetition Nd:YLF pulse laser. Theoretically, it can capture velocity fields at 20 fps with a reduced spatial resolution. In order to validate its performance, the dynamic PIV system was applied to a turbulent jet of which Reynolds number is about 3000. The particle images of 1024$\times$512 pixels were captured at a sampling rate of 4 KHz. The dynamic PIV system measured successfully the temporal evolution of instantaneous velocity fields of the turbulent jet, from which spectral analysis of turbulent structure was also feasible.

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Flow Analysis around a Floating Cylinder in a Swirl Flow with a Stereoscopic-PIV (스테레오 PIV에 의한 원관내 선회유동중 실린더형 부유체 주위 유동 특성 해석)

  • Doh, D.H.;Hwang, T.G.;Tanaka, K.;Takei, M.
    • 유체기계공업학회:학술대회논문집
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    • pp.319-322
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    • 2006
  • The flow characteristics around a floating cylinder in a swirling flow field in a vertical pipe with a length of 600mm and an inner diameter of 100mm is investigated by the use of the Stereoscopic-PIV system. The measurement system consists of two cameras, a Nd-Yag laser and a host computer. Optical sensors(LEDs) were used to detect the location of the floating cylinder and to activate the Stereoscopic-PIV system. A conditional sampling Stereoscopic-PIV system was developed in which the flow fields around the floating cylinder are measured at the events of the activations. It has been verified that the motion of the floating cylinder becomes stable when the azimuthal velocity component of the swirl flow is maintained at stable states.

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An Experimental Study of Developing and Fully Developed Flows in a Wavy Channel by PIV

  • Kim, Sung-Kyun
    • Journal of Mechanical Science and Technology
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    • v.15 no.12
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    • pp.1853-1859
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    • 2001
  • An experimental study is presented for a flow field in a two dimensional wavy channels by PIV. This flow has two major applications such as a blood flow simulation and the enhancement of heat transfer in a heat exchanger. While the numerical flow visualization results have been limited to the fully developed cases, existing experimental results of this flow were simple qualitative ones by smoke or dye streak test. Therefore, the main purpose of this study is to produce quantitative flow data for fully developed and developing flow regimes by the Correlation Based Correction PIV (CBC PIV) and to conjecture the analogy between flow characteristics and heat transfer enhancement with low pumping power. Another purpose of this paper is to examine the onset position of the transition and the global mixing, which results in transfer enhancement. PIV results on the Fully developed and developing flow in a wavy channel at Re=500, 1000 and 2000 are obtained. for the case Reynolds Number equals 500, the PIV results are compared with the finite difference numerical solution.

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Development of a Recursive Local-Correlation PIV Algorithm and Its Performance Test

  • Daichin Daichin;Lee Sang Joon
    • 한국가시화정보학회:학술대회논문집
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    • pp.75-85
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    • 2001
  • The hierarchic recursive local-correlation PIV algorithm with CBC(correlation based correction) method was developed to increase the spatial resolution of PIV results and to reduce error vectors. This new algorithm was applied to the single-frame and double-frame cross-correlation PIV techniques. In order to evaluate its performance, the recursive algorithm was tested using synthetic images, PIV standard images from Visualization Society of Japan, real flows including ventilation flow inside a vehicle passenger compartment and wake behind a circular cylinder with rib let surface. As a result, most spurious vectors were suppressed by employing CBC method. In addition, the hierarchical recursive correlation algorithm improved largely the sub-pixel accuracy of PIV results by decreasing the interrogation window size, increasing spatial resolution significantly.

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Dual-plane Stereoscopic PIV Measurement on the Lobed Jet Mixing Flow

  • SAGA Tetsuo;KOBAYASHI Toshio
    • 한국가시화정보학회:학술대회논문집
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    • pp.108-122
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    • 2001
  • In a continuing effect to study the mixmg enhancement by large-scale streamwise vortices in lobed mixing flows, an advanced PIV system named as dual-plane stereoscopic PIV system was used in the present study to conduct simultaneous vorticity (all three components) measurement of an air jet exhausted from a lobed nozzle. Unlike 'classical' 2-D PIV system or conventional 'single-plane' stereoscopic PIV system, the dual-plane stereoscopic PIV system used in the present study can obtain the flow velocity (all three components) fields at two spatially separated planes simultaneously. Therefore, it can provide the distributions of all the three components of vorticity vectors instantaneously and simultaneously. The evolution and interaction characteristics of the large-scale streamwise vortices and azimuthal Kelvin-Helmholtz vortices in the lobed jet mixing flow were revealed instantaneously and quantitatively from the measurement results of the dual-plane stereoscopic PIV system. The characteristics of the mixing process in the lobed jet mixing flow were analyzed based on the simultaneous measurement results of the steamwise vorticity and azimuthal Kelvin-Helmholtz vorticity distributions.

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Animation construction and application example by the post-processing of PIV data (PIV데이터의 post-processing에 의한 애니메이션 제작 및 적용예)

  • Kim, M.Y.;Choi, J.W.;Lee, H.;Lee, Y.H.
    • Proceedings of the KSME Conference
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    • pp.655-660
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    • 2000
  • Animation technique from the PIV database is particularly emphasized to give macroscopic and quantitative description of complex flow fields. This paper shows animation construction and application example for the post-processing of PIV data. As examples, first case is a pitching airfoil immersed in tree surface water circulating tunnel. Second case is a wake of a model-ship. Third case of PIV data is a large scale surface flow field. Obtained images are processed in time sequence by PIV exclusive routines where an efficient and reliable cross correlation algorithm is included for vector identification. All. animation Jobs are implemented completely on single personal computer environment. Compressed digital images are obtained initially by Motion-JPEG board and various An files are finally obtained through graphic processes.

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