• Title, Summary, Keyword: 입자영상속도계

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A Study on the Blood Flow Characteristics in the Abodminal Aortic Aneurysm (대동맥류 내부 혈류 유동 특성에 관한 연구)

  • 오태헌;김상욱;이계한
    • Journal of Biomedical Engineering Research
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    • v.20 no.5
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    • pp.601-608
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    • 1999
  • 동맥의 일부분의 팽창하는 동맥류는 높은 사망률을 야기하는 혈관계 질환이다. 동맥류의 발생 및 파열에는 동맥류 내부의 혈류의 유동에 의한 혈관벽 전단 응력 및 압력이 주용한 원인 중 하나로 의심되고 있다. 복부대동맥류 내부의 혈류 유동 특성을 밝히기 위해서 동맥류의 최대 확장부가 복부동맥의 1.5배, 2배인 유리 모델을 제작하였다. 정상류 상태에서 다양한 레이놀즈수에 대해서 속도 및 난동도를 입자영상속도계를 이용하여 측정하였다. 경계층 박리로 인한 재순환 부분이 끝나는 재부착점은 동맥류 최대 확장부 후부에서 발생하였으며, 이 위치는 레이놀즈수의 변화에 따라 바뀌었다. 축방향 속도의 난동은 최대 확장부 후부에서 크게 나타났으며, 이 위치에서 난동에 의한 부가적 응력이 크며 혈관벽 구조변화가 발생하리라 예측된다. 동맥류 내부의 압력분포는 수치해석에 의해 계산되었다. 동맥류 내부 압력은 크기가 증가함에 따라 커졌으며 압력은 동맥류 최대 확장부 후부에서 발생하는 재부착점에서 최대값을 나타내었다. 동맥류 최대확장부 후부는 압력이 최대값을 가지며, 전단력의 변화 및 난동이 큰 지역이므로 동맥류의 파열이 발생하기 쉬운 지역으로 예측된다.

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Development of Wall Flow Sensor Using Micro Imaging Device (미세 영상 장치를 이용한 벽면 유동 센서 개발)

  • Lee, Seung Hwan;Kim, Byung Soo;Kim, Hyoung-Bum
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.12
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    • pp.1217-1222
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    • 2012
  • A wall flow sensor has been used for feedback flow control and wall shear stress measurement. In this study, we developed a new wall flow sensor by combining the PIV algorithm and the micro image sensor used in an optical mouse. The feasibility of the wall flow sensor was investigated by using simulated fluid flow experiments. Compared with the quadrature signal from imaging devices, the accuracy of the wall flow velocity measurement was improved and the dynamic range increased. In addition, the depth information of particles was also measured by using the defocusing imaging technique.

Flow Field Separating Technique in Bubbly Flow using Discrete Wavelet (이산 웨이블릿을 이용한 Bubbly flow의 유통분리기법)

  • Jo, Hyo-Jae;Doh, Deog-Hee;Choi, Je-Eun;Takei, Masahiro;Kang, Byung-Yoon
    • Journal of Navigation and Port Research
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    • v.32 no.10
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    • pp.777-783
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    • 2008
  • Nowadays wavelet transforms are widely used for the analyses of PIV velocity vector fields. This is bemuse the wavelet provides not only spatial information of the velocity vectors but also of time and frequency domains. In this study, a discrete wavelet trC1f1$form has been applied to real PIV images of bubbly flows. The vector fields obtained by a self-made cross-correlation PIV algorithm were used for the discrete wavelet transform The performances of the discrete wavelet transform is investigated by changing the level of power of discretization. The decomposed images by the wavelet multiresolution showed conspicuous characteristics of the bubbly flows according to the level changes. The high spatial bubble concentrated area could be evaluated by the constructed discrete wavelet transform algorithm, at which high leveled wavelets could play a dominant roles to reveal the flow characteristics.

A Study on Simultaneous Analysis of Velocity and Density Distributions for High-Speed $CO_{2}$ Flow (고속 이산화탄소 유동장의 속도 및 밀도 동시 분석에 관한 연구)

  • Kim Yong-Jae;Ko Han Seo;Okamoto Koji
    • 한국가시화정보학회:학술대회논문집
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    • pp.40-45
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    • 2005
  • Velocity and density distributions of a high-speed and initial $CO_{2}$ jet flow have been analyzed simultaneously by a developed three-dimensional digital speckle tomography and a particle image velocimetry(PIV). Three high-speed cameras have been used for tomography and PIV since a shape of a nozzle for the jet flow is asymmetric and the initial flow is fast and unsteady, The speckle movements between no flow and $CO_{2}$ jet flow have been obtained by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields for the high-speed $CO_{2}$ jet flow have been reconstructed from the deflection angles by a real-time tomography method and the two-dimensional velocity fields have been calculated by a PIV method simultaneously and instantaneously.

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Study on Quantitative Visualization Using Bubble Tracer in a Cavitation Tunnel (공동수조에서 추종입자로서 기포를 이용한 정량적 가시화에 대한 연구)

  • Paik, Bu-Geun;Kim, Kyung-Youl;Cho, Seong-Rak;Ahn, Jong-Woo
    • Journal of the Korean Society of Visualization
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    • v.5 no.1
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    • pp.22-29
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    • 2007
  • In the present study, naturally generated bubbles were investigated to be sure if they could be adopted as the tracer for PIV techniques. The bubble can be grown from the nuclei melted in the water of tunnel and the size of bubbles is changed through the variation of tunnel pressure. Since the trace ability and appropriate size of tracer are so important for PIV techniques, the characteristics of bubbles as tracer are revealed in terms of trace ability and bubble size with the variation of flow speed and tunnel pressure in this study. In addition, PIV measurements of (low behind a rotating propeller are conducted to confirm the trace ability of bubbles even in a highly vortical flow.

PIV Velocity Field Measurements of Flow around a Ship with Rotating Propeller (PIV를 이용한 선박 프로펠러 후류의 속도장 계측)

  • 이상준;백부근
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.5
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    • pp.17-25
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    • 2003
  • Velocity field behind a container ship model with a rotating propeller has been investigated using PIV (particle image velocimetry) system. Four hundred instantaneous velocity fields were measured at 4 different blade phases and ensemble-averaged to investigate the spatial evolution of vortical structure of near wake within one propeller diameter downstream. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed due to the boundary layers developed on the blade surfaces. The interaction between bilge vortex developed along the hull surface and the tangential velocity component of incoming flow causes to have asymmetric flow structure in the transverse plane.

Visualization of the flow between co-rotating disks in shroud with an obstruction (장애물을 포함한 동시회전 디스크 내부의 비정상 유동가시화)

  • 공대위;도덕희;주원구
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1152-1156
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    • 2003
  • Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. PIV measurement was used fer the unsteady flow between the center pair of four disks of four times larger than common radius of HDD disk at several rpm in a fixed cylindrical enclosure. The boundary between inner region and outer region is detected using PIV measurement and the number of dominant vortices s determined clearly. Tip vortices generated by an obstruction with actual-like configuration can be found at inner region. Oscillating flow from the obstruction appears at outer region with complex flow pattern.

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Changes of Blood Flow Characteristics for different Coil Locations after the Embolisation of Lateral Aneurysms (측방 동맥류 색전술 후 코일 위치에 따른 혈류 유동의 변화)

  • 이계한;송계웅;변홍식
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.124-127
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    • 2002
  • Ceil embolisation technique has been used to treat the intracranial aneurysms. Microcoils inserted into the aneurysm sac induce the blood flow stagnation inside the aneurysm sac, which causes the thrombus formation and embolisation of aneurysm. Since the intraaneurysmal flow patterns affect the embolisation process, we want to measure the flow field for different locations of coil inside the aneurysm sac . Lateral aneurysm models are manufactured using rapid prototyping, and the velocity fields are measured using particle image velocitimeter. Distally blocked models showed less flow into the aneurysm sac comparing to proximally blocked models. Also blocking the neck of aneurysm showed better inflow blocking comparing to blocking the dome of aneurysm. These results suggest that distal neck should be the preferred locations of coil for aneurysm embolisation.

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Water Tunnel Test to Simulate Internal Flows of a Solid Rocket Motor (고체추진 내부유동 모사를 위한 수동시험)

  • Kim, Hye-Ung;Kang, Seung-Hee
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.181-184
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    • 2009
  • In this study, flow visualization method to simulate internal flows of solid rocket motor in a water tunnel is introduced. The tunnel provides excellent visualization of vortex flows and has been used to propellant grain design of the solid rocket motor. A water tunnel is suggested for the research and the visualization test using dye, hydrogen bubble generator and PIV has been studied and discussed.

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