• Title/Summary/Keyword: PIV

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Measurement of Thermal Flow in a Hele-Shaw Convection Cell Using Holographic Interferometry and PIV Technique (홀로그래픽 간섭계와 PIV를 이용한 Hele-Shaw Convection Cell 내부 열유동 해석)

  • Kim Seok;Lee Sang-Joon
    • 한국가시화정보학회:학술대회논문집
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    • 2002.11a
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    • pp.35-38
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    • 2002
  • Variations of temperature and velocity fields in a Hele-Shaw Convection Cell (HSC) were measured using a holographic interferometry and PIV technique with varying Rayleigh number. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow at high Rayleigh numbers. Two different measurement methods of holographic interferometry, double-exposure method and real-time method, were employed to measure the temperature field variations of HSC convective flow. In the double-exposure method, unwanted waves can be eliminated and reconstruction images are clear, but transient flow structure cannot be observed clearly. On the other hand, transient flow can be observed and reconstructed well using the real-time method. PIV results show that flow inside the HSC is periodic and the oscillating state is well matched with the temperature field results. The holographic interferometry and PIV techniques employed in this study are useful for analyzing the unsteady convective thermal fluid flows.

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Papers : A Study on the Characteristics of the Ramjet Engine Combustor using a Two Color PIV Technique (논문 : Two Color PIV 기법을 이용한 램제트엔진 연소기 특성에 대한 연구)

  • An,Gyu-Bok;Yun,Yeong-Bin;Jeong,In-Seok;Heo,Hwan-Il
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.1
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    • pp.95-104
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    • 2002
  • A two color PIV technique has been developed for visualization of complex and high speed flow in a ramjet combustor. Two color PIV has the advantages that velocity distribytions in high speed flowfields can be measured simply by varying the time interval between two different laser beams and a directional ambiguity problem can be solved by color separation, and then a singnal-to-noise ratio can be increased through nearly perfect cross-correlation. As a basic research of the ramjet engine, a 2-D shaped combustor with two symmetric air intakes has been manufactured and an experimental study has been conducted using a two color PIV technique. The flow characteristics such as recirculation zones and two intake air mixing have been investigated varying inlet angles and dome heights. It is found that the size and air mass ratio of reciculation zones are affected mainly by an inlet angle, but not much by a dome height.

On the Viscous Flow Around Breaking Waves Generated by a Submerged Cylinder(Part 3 : Survey of Flow Field Using PIV Technique) (몰수실린더에 의하여 생성되는 쇄파주위 점성유동의 고찰(제3부 : PIV를 이용한 순간유동장 해석))

  • B.S. Hyun;Y.H. Shin;K.S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.37 no.2
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    • pp.38-45
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    • 2000
  • A breaking-wave caused by a cylinder moving under the free-surface is studied, which is designed to unveil the interaction between breaker and cylinder using PIV at CWC. The detailed structures of the vortical flow is obtained from the velocity field measured by PIV technique. The vorticity distribution behind the breaker and originated from the breaker. It has been obvious that the vortices from breaker greatly affect the whole wake field at S/D=1. Certainly PIV was confirmed to be a very versatile means to investigate the complex flow fields such as breaking wave.

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Ultrasonic Applications for the Enhancement of Turbulence Flow by using the PIV Measurement (PIV계측을 이용한 난류유동의 증진을 위한 초음파 적용)

  • Park, Y.H.;Choi, W.C.;Koo, J.H.;Song, M.G.;Ju, E.S.
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.633-638
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    • 2000
  • Ultrasonic applications for the enhancement of turbulence flow by using the PIV measurement were carried out according to the angle of the ultrasonic oscillator, materials of the reflector and each section when ultrasonic is reflected several times. Angles of the ultrasonic oscillator such as $30^{\circ},\;45^{\circ},\;60^{\circ},\;90^{\circ},\;120^{\circ},\;135^{\circ}$ and $150^{\circ}$ were selected, and turbulent intensities were compared at Reynolds No. 2,000 and 4,000. Materials of the reflector such as wood, acryl, iron and glass were selected, and time mean velocity vector and turbulent intensity were compared at Reynolds No. 4,000. The zone which was observed was selected from first section to fourth section when ultrasonic was reflected several times. Every data such as time mean velocity vector and time mean turbulent intensity which was obtained by PIV measurement was examined, compared and discussed at Reynolds No. 2,000 and 4,000 to know the degree of turbulence enhancement in each case.

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In vitro application of Angiographic PIV technique to blood flows (Angiographic PIV 기법을 이용한 혈액유동의 in-vitro 연구)

  • Kim, Guk-Bae;Lim, Nam-Yun;Jung, Sung-Yong;Lee, Sang-Joon
    • 한국가시화정보학회:학술대회논문집
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    • 2007.11a
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    • pp.105-108
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    • 2007
  • To diagnose the vascular diseases from the viewpoint of hemodynamics, we need 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. For investigating in-vivo hemodynamic phenomena of vascular circulatory diseases, a new diagnosing technique combining a medical radiography and PIV method was newly developed. This technique called 'Angiographic PIV system' consists of a medical X-ray tube, an X-ray CCD camera, a shutter module for generating double pulse-type X-ray, and a synchronizer. Through several preliminary tests, the feasibility of the Angiographic PIV technique was verified. For in-vivo applications to real blood flows, we developed tracer microcapsules, which were optimized to this system, made of a contrast material of iodine and a matrix material of PVA (polyvinylpyrrolidone). In near future, the Angiographic PIV technique will be used for understanding hemodynamic phenomena of vascular diseases and for their early detection.

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Development of a High Resolution Digital Cinematic Particle Image Velocimetry (고해상도 Cinematic PIV의 개발)

  • Park, Gyeong-Hyeon;Kim, Gyeong-Cheon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.11
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    • pp.1535-1542
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    • 2001
  • A high resolution digital cinematic Particle Image Velocimetry(PIV) has been developed. The system consists of a high speed CCD camera, a continuous Ar-ion laser and a computer with camera controller. To improve the spatial resolution, we adopt a Recursive Technique for velocity interrogation. At first, we obtain a velocity vector fur a larger interrogation window size based on the conventional two-frame cross-correlation PIV analysis using the FFT algorithm. Based on the knowing velocity information, more spatially resolved velocity vectors are obtained in the next iteration step with smaller interrogation windows. When the correct velocity vector at the first step is found to be critical, a Multiple Correlation Validation(MCV) technique is applied to decrease the spurious vectors. The MCV technique turns out to improve SNR(Signal to Noise Ratio) of the correlation table. The developed cinematic PIV method has been applied to the measurement of the unsteady flow characteristics of a Rushton turbine mixer. A total of 3,245 instantaneous velocity vectors were successfully obtained with 4 ms time resolution. The acquired spatial resolution corresponds to the conventional high resolution digital PIV system using a 1K ${\times}$ 1K CCD camera.

Study on the Three Dimensional Flow Characteristics of the Propeller Wake Using PIV Techniques (PIV 기법을 이용한 프로펠러 후류의 3차원 유동 특성 연구)

  • Paik, Bu-Geun;Kim, Jin;Kim, Kyung-Youl;Kim, Ki-Sup
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.3 s.153
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    • pp.219-227
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    • 2007
  • A stereo-PIV (particle image velocimetry) technique is used to investigate the vortical structure of the wake behind a rotating propeller in the present study. A four bladed propeller is tested in a cavitaion tunnel without any wake screen. Hundreds of instantaneous velocity fields are phase-averaged to reveal the three dimensional spatial evolution of the flow behind the propeller. The results of conventional 2-D PIV are also compared with those of the stereo-PIV to understand the vortical structure of propeller wake deeply. The variations of radial and axial velocities in the 2-D PIV results seem to be affected by the out-of-plane motion. generating a little perspective error in the in-plane velocity components of the slipstream. The strong out-of-plane motion around the hub vortex also causes the perspective error to vary the axial velocity component a little at the near wake region. The out-of-plane velocity component had the maximum value of about 0.3U0 in the tip vortices and continued its magnitude in the wake region.

Clinical significance of codetection of the causative agents for acute respiratory tract infection in hospitalized children (급성 호흡기 감염으로 입원한 소아에서 호흡기 감염의 원인: 중복검출의 임상적 의미)

  • Roh, Eui Jung;Chang, Young Pyo;Kim, Jae Kyung;Rheem, In Soo;Park, Kwi Sung;Chung, Eun Hee
    • Clinical and Experimental Pediatrics
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    • v.52 no.6
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    • pp.661-666
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    • 2009
  • Purpose : To determine the prevalence and clinical features of codetected respiratory etiological agents for acute respiratory infection in hospitalized children. Methods : Nasopharyngeal aspirates were obtained from hospitalized children with acute respiratory infection at Dankook University Hospital from September 2003 through June 2005. Immunofluorescent staining and culture were used for the detection of respiratory viruses (influenza virus [IFV] types A, B; parainfluenza virus [PIV] types 1, 2, 3; respiratory syncytial virus [RSV]; adenovirus [AdV]). Polymerase chain reaction (PCR) assays were used for Mycoplasma pneumoniae (MP) and Chlamydia trachomatis (CT) detection, and PCR and culture were performed for enterovirus detection. Acid-fast staining and culture were performed for tuberculosis detection. The demographic and clinical characteristics were reviewed retrospectively from the patients medical records. Results : Evidence of two or more microbes was found in 28 children: RSV was detected in 14, PIV 3 in 10, AdV in 10, MP in 8, PIV 2 in 8, CT in 4, and PIV 1 in 3. Codetected agents were found as follows: RSV+PIV 2, 6 patients; AdV+MP, 4 patients; AdV+PIV, 3 patients; RSV+MP, 3 patients; PIV 1+PIV 3, 3 patients. Distinct peaks of codetected agents were found in epidemics of MP and each respiratory virus. Conclusion : The codetected infectious agents were RSV, PIV, AdV, and MP, with distinct peaks found in epidemics of MP and each respiratory virus. Although advances in diagnostic methods have increased the prevalence of codetection, its clinical significance should be interpreted cautiously.

Measurement of Flow Field in a Ginseng Cleaner Model Using PIV (PIV에 의한 인삼세척기 모델 내부의 유동계측)

  • 송치성
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.1
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    • pp.139-145
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    • 2001
  • The objective of experimental study is to apply simultaneous measurement by PIV(Particle Image Velocimetry) to high_speed flow characteristics within ginseng cleaner model. Three different kinds of flow rate(15. 20, 27l/min) are selected as experimental condition. Optimized cross correlation identification to obtain velocity distribution, time-mean velocity distribution, velocity, profile, kinetic energy and turbulence intensity are represented quantitatively for the deeped understanding of the flow characteristics in a ginseng cleaner model.

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