• Title, Summary, Keyword: Dynamic PIV

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Measurement of turbulent jet flow using dynamic PIV technique (Dynamic PIV를 이용한 난류 제트유동 해석)

  • Lee Sang-Joon;Jang Young-Gil;Kim Seok
    • 한국가시화정보학회:학술대회논문집
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    • pp.36-39
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    • 2005
  • Information on temporal evolution of whole velocity fields is essential for physical understanding of a complicated turbulent flow and was obtainable using dynamic PIV because of advances of high-speed imaging technique, laser and electronics. A dynamic PIV systme consists of a high-speed CMOS camera having $1K\times1K$ pixels resolution at 1 KHz and a high-repetition Nd:Yag pulse laser. In order to validate its performance, the dynamic PIV system was applied to a turbulent jet whose Reynolds number is about 3000. The particle images of $1024\times512$ 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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Development of higher performance algorithm for dynamic PIV

  • NISHIO Shigeru
    • 한국가시화정보학회:학술대회논문집
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    • pp.25-32
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    • 2004
  • The new algorithm for higher performance of dynamic PIV has been proposed. Present study considered mathematical basis of PIV analysis for multiple-time-step images and it enables us to analyze the high time-resolution PIV, which is obtained by dynamic PIV system. Conventional single pair image PIV analysis gives us the velocity field data in each time step but it sometimes contains unnecessary information of target flow. Present technique utilize multi-time step correlation information, and it is analyzed.

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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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Dynamic PIV Measurement of Swirl Flow in a PC Fan

  • ARAMAKI Shinichiro;HAYAMI Hiroshi
    • 한국가시화정보학회:학술대회논문집
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    • pp.41-45
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    • 2004
  • The dynamic particle image velocimetry (PIV) is consisted of a high frequency pulse laser, high speed cameras and a timing controller. The three velocity components of flow downstream of an axial flow fan for PC cooling system are measured using the dynamic PIV system. An Axial flow fan has seven blades of 72 mm in diameter. The rotating speed is 1800 rpm. The downstream flow is visualized by smoke particles of about $0.3-1\;{\mu}m$ in diameter. The three-dimensional instantaneous velocity fields are measured at three downstream planes. The swirl velocity component was diffused downstream and the change in time-mean vorticity distribution downstream was also discussed. The spatio-temporal change in axial velocity component with the blades passing is recognized by the instantaneous vector maps. And the dynamic behavior of vorticity moving with the rotating blades is discussed using the unsteady vorticity maps.

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Visualization of micro-interfacial conditions using Micro PIV

  • OKAMOTO Koji;SHINOHARA Kyosuke;SUGII Yasuhiko
    • 한국가시화정보학회:학술대회논문집
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    • pp.111-118
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    • 2004
  • A new micro-resolution PIV (Particle Image. Velocimetry) has been developed. To investigate transient phenomena in a microfluidic device, Dynamic micro-PIV system was realized by combining a high-speed camera and a CW(Continuous Wave) laser. The technique was applied to a micro-counter-current flow, consisting of water and butyl acetate. The velocity fields of water in the micro counter-current flow were visualized for a time resolution of 500 $\{mu}s$ and a spatial resolution of 2.2 x 2.2 $\{mu}m$. Using the Dynamic micro-PIV technique, the vortex-like motions of fluorescent particles at the water-butyl acetate interface were captured clearly

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Dynamic PIV analysis of High-Speed Flow Ejected from the Inflator Housing of a Curtain-type Airbag (Dynamic PIV를 이용한 커튼형 에어백 부품림 장치의 유동해석)

  • Jang, Young-Gil;Kim, Seok;Lee, Sang-Joon
    • 유체기계공업학회:학술대회논문집
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    • pp.407-408
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    • 2006
  • Passenger safety is one of the most important considerations in the purchase of an automobile. A curtain-type air bag is increasingly adapted in deluxe cars for protecting passengers from the danger of side clash. Inflator housing is a main part of the curtain-type air bag system for supplying high-pressure gases to pump up the air bag-curtain. Although the inflator housing is fundamental in designing a curtain-type air bag system, flow information on the inflator housing is very limited. In this study, we measured instantaneous velocity fields of a high-speed flow ejecting from the inflator housing using a dynamic PIV system. From the velocity field data measured at a high frame-rate, we evaluated the variation of the mass flow rate with time. From the instantaneous velocity fields of flow ejecting from the airbag inflator housing in the initial stage, we can see a flow pattern of broken shock wave front and its downward propagation. The flow ejecting from the inflator housing was found to have large velocity fluctuations and the maximum velocity was about 700m/s. The velocity of high-speed flow was decreased rapidly and the duration of high-speed flow over 400m/s was maintained only to 30ms. After 100ms, there was no perceptible flow.

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A Study on the Dynamic Stall Characteristics of an Elliptical Airfoil by Flow Pattern Measured by PIV (PIV 측정 흐름형태에 의한 타원형 날개꼴의 동적 실속 특성 연구)

  • Lee, Ki-Young;Sohn, Myong-Hwan;Jung, Hyong-Seok
    • Journal of the Korea Institute of Military Science and Technology
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    • v.8 no.3
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    • pp.116-123
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    • 2005
  • An experimental investigation on the static and dynamic stall characteristics of elliptic airfoil was performed by PIV velocity field measurements. The flow Reynolds number was $3.13{\times}10^5$ and the reduced frequency of the pitch oscillation ranged from 0.075 to 0.125. The onset of static stall was caused by boundary layer separation which started at the trailing edge and progressed toward the leading edge. However, dynamic stall was caused by the vortex shed at the leading edge region and the flow field showed a vortex dominated flow with turbulent separation and alternate vortex shedding. The increase of reduced frequency increased the dynamic stall angle of attack and intensified the flow hysteresis in the down-stroke phase.

A Research on the Vector Search Algorithm for the PIV Flow Analysis of image data with large dynamic range (입자의 이동거리가 큰 영상데이터의 PIV 유동 해석을 위한 속도벡터 추적 알고리즘의 연구)

  • Kim Sung Kyun
    • 한국전산유체공학회:학술대회논문집
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    • pp.13-18
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    • 1998
  • The practical use of the particle image velocimetry(PIV), a whole-field velocity measurement method, requires the use of fast, reliable, computer-based methods for tracking velocity vectors. The full search block matching, the most widely studied and applied technique both in area of PIV and Image Coding and Compression, is computationally costly. Many less expensive alternatives have been proposed mostly in the area of Image Coding and Compression. Among others, TSS, NTSS, HPM are introduced for the past PIV analysis, and found to be successful. But, these algorithms are based on small dynamic range, 7 pixels/frame in maximum displacement. To analyze the images with large displacement, Even and Odd field image separation and a simple version of multi-resolution hierarchical procedures are introduced in this paper. Comparison with other algorithms are summarized. A Results of application to the turbulent backward step flow shows the improvement of new algorithm.

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Experimental Study on Turbulent Structure of Flow over a Micro Riblet Plate (미세 Riblet 평판에서의 난류구조 변화에 관한 실험적 연구)

  • Choi, Yong-Seok;Lee, Sang-Joon
    • 유체기계공업학회:학술대회논문집
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    • pp.375-376
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    • 2006
  • Turbulent structure of a boundary-layer over a flat plate coated with micro riblet film(MRF) has been investigated experimentally. The turbulent structure was visualized using a dynamic particle image velocimetry (Dynamic PIV) system. We identified the vortex structures from 2-D velocity field data by applying the complex eigenvalue definition. The velocity field images acquired by using the complex eigenvalue definition showed the whole 2-D vortex structures clearly. In addition, the spatial distributions of small-scale vortices as well as large-scale vortices were obtained with high accuracy. The difference of vortex structures between the MRF coated flat plate and the smooth flat plate was analysed in detail. With varying upstream flow speed, the characteristics of vortex structure over the MRF coated flate plate was compared with those over the smooth flat plate.

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Dynamic PIV analysis of High-Speed Flow from Vent Holes of Fill-Hose in Curtain type Airbag (Dynamic PIV 기법을 이용한 커튼에어백 Vent Hole 고속유동 해석)

  • Jang, Young-Gil;Choi, Yong-Seok;Lee, Sang-Joon
    • 한국가시화정보학회:학술대회논문집
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    • pp.17-20
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    • 2006
  • Passenger safety is fundamental factor in automobile. Among much equipment for passenger safety, the air bag system is the most fundamental and effective device. Beside of the front air bag system which installed on most of all automobiles, a curtain-type air bag is increasingly adapted in deluxe cars fur protecting passengers from the danger of side clash. Curtain type airbag system consists of inflator housing, fill hose, curtain airbag. Inflator housing is a main part of the curtain-type air bag system for supplying high-pressure gases to deploy the air bag-curtain. Fill hose is a passageway to carry the gases from inflator housing to each part of curtain airbag. Therefore, it is very important to design the vent holes of fill hose for good performance of airbag deployment. But, the flow information from vent holes of fill hose is very limited. In this study, we measured instantaneous velocity fields of a high-speed flow ejecting from the vent holes of fill hose using a dynamic PIV system. From the velocity Held data measured at a high frame-rate, we evaluated the variation of the mass flow rate with time. From the instantaneous velocity fields of flow ejecting from the vent holes in the initial stage, we can see a flow pattern of wavy motion and fluctuation. The flow ejecting from the vent holes was found to have very high velocity fluctuations and the maximum velocity was about 480m/s at 4-vent hole region. From the mass flow rate with time, the accumulated flow of 4-vent hole has occupied about 70% of total flow rate.

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