• Title, Summary, Keyword: PIV

Search Result 1,283, Processing Time 0.046 seconds

Comparison of Velocity Fields of Wake behind a Propeller Using 2D PIV and stereoscopic PIV (2D PIV와 stereoscopic PIV 기법으로 측정한 프로펠러 후류의 속도장 비교 연구)

  • Paik Bu-Geun;Lee Sang-Joon
    • 한국가시화정보학회:학술대회논문집
    • /
    • /
    • pp.23-26
    • /
    • 2002
  • The phase-averaged velocity fields of 3 dimensional turbulent wake behind a marine propeller measured by 2D PIV and stereoscopic PIV(SPIV) were compared directly. In-plane velocity fields obtained from the consecutive particle images captured by one camera in 2D PIV have perspective errors due to out-of-plane motion. However, the perspective errors can be removed by measuring three component velocity fields using SPIV method with two cameras. It is also necessary to measure three components velocity fields for the investigation of complicated near-wake behind the propeller for the suitable propeller design. 400 instantaneous velocity fields were measured for each of four different blade phases of $0^{\circ},\;18^{\circ},\;36^{\circ}C\;and\;54^{\circ}$. They were ensemble averaged to investigate the spatial evolution of the propeller wake in the downstream region. The phase-averaged velocity fields show the viscous wake developed along the blade surfaces and tip vortices were formed periodically. The perspective errors caused by the out-of-plane motion was estimated by the comparison of 2D PIV and SPIV results. The difference in the axial mean velocity fields measured by both techniques are nearly proportional to the mean out-of-plane velocity component which has large values in the regions of the tip and trailing vortices. The axial turbulence intensity measured by 2D PIV was overestimated since the out-of-plane velocity fluctuations influence the in-plane velocity vectors and increase the in-plane turbulence intensities.

  • PDF

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

  • Daichin Daichin;Lee Sang Joon
    • 한국가시화정보학회:학술대회논문집
    • /
    • /
    • pp.75-85
    • /
    • 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.

  • PDF

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

  • SAGA Tetsuo;KOBAYASHI Toshio
    • 한국가시화정보학회:학술대회논문집
    • /
    • /
    • pp.108-122
    • /
    • 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.

  • PDF

Evaluation of Recursive PIV Algorithm with Correlation Based Correction Method Using Various Flow Images

  • Daichin;Lee, Sang-Joon
    • Journal of Mechanical Science and Technology
    • /
    • v.17 no.3
    • /
    • pp.409-421
    • /
    • 2003
  • The hierarchical recursive local-correlation PIV algorithm with CBC (correlation based correction) method was employed to increase the spatial resolution of PIV results and to reduce error vectors. The performance of this new PIV algorithm was tested using synthetic images, PIV standard images of Visualization Society of Japan, real flows including ventilation flow inside a vehicle passenger compartment and wake behind a circular cylinder with riblet surface. As a result, most spurious vectors were suppressed by employing the CBC method, the hierarchical recursive correlation algorithm improved the sub-pixel accuracy of PIV results by decreasing the interrogation window size and Increased spatial resolution significantly. However, with recursively decreasing of interrogation window size, the SNR (signal-to-noise ratio) in the correlation plane was decreased and number of spurious vectors was increased. Therefore, compromised determination of optimal interrogation window size is required for given flow images, the performance of recursive algorithm is also discussed from a viewpoint of recovery ratio and error ratio in the paper.

PIV Measurement on Airflows in the Abnormal Nasal Cavity with the Adenoid Vegetation (아데노이드 비대증에 의한 비정상 비강 내 유동의 PIV해석)

  • Kim, Sung-Kyun;Son, Young-Rak
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.27 no.4
    • /
    • 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.

Micro-PIV Analysis of Electro-osmotic Flow inside Microchannels (마이크로 채널 내부 전기삼투 유동에 대한 PIV유동 해석)

  • Kim Yang-Min;Lee Sang-Joon
    • Journal of the Korean Society of Visualization
    • /
    • v.1 no.2
    • /
    • pp.47-51
    • /
    • 2003
  • Microfluidic chips such as lab-on-a-chip (LOC) include micro-channels for sample delivery, mixing, reaction, and separation. Pressure driven flow or electro-osmotic flow (EOF) has been usually employed to deliver bio-samples. Having some advantages of easy control, the flow characteristics of EOF in microchannels should be fully understood to effectively control the electro-osmotic pump for bio-sam-pie delivery. In this study, a micro PIV system with an epifluorescence inverted microscope and a cooled CCD was used to measure velocity fields of EOF in a glass microchannel and a PDMS microchannel. The EOF velocity fields were changed with respect to electric charge of seeding particles and microchannel materials used. The EOF has nearly uniform velocity distribution inside the microchannel when pressure gradient effect is negligible. The mean streamwise velocity is nearly proportional to the applied electric field. Glass microchannels give better repeatability in PIV results, compared with PDMS microchannels which are easy to fabricate and more suitable for PIV experiments.

  • PDF

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

  • Kim, Sung-Kyun
    • Journal of Mechanical Science and Technology
    • /
    • v.15 no.12
    • /
    • pp.1853-1859
    • /
    • 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.

  • PDF

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
    • /
    • /
    • pp.655-660
    • /
    • 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.

  • PDF

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
    • /
    • /
    • pp.319-322
    • /
    • 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.

  • PDF

Development of angiographic PIV and performance evaluation (Angiographic PIV기법 개발 및 성능 평가)

  • Jung, Sung-Yong;Kim, Guk-Bae;Lim, Nam-Yun;Lee, Sang-Joon
    • 한국전산유체공학회:학술대회논문집
    • /
    • /
    • 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.

  • PDF