• Title/Summary/Keyword: Instantaneous intensity

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Simultaneous Measurement of Velocity and Concentration Field in a Stirred Mixer Using PIV/LIF Technique (PIV/LIF기법에 의한 교반혼합기 내의 속도장과 농도장 동시 측정)

  • Jeong, Eun-Ho;Yoon, Sang-Youl;Kim, Kyung-Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.4
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    • pp.504-510
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    • 2003
  • Simultaneous measurements of turbulent velocity and concentration field in a stirred mixer tank are carried out by using PIV/LIF technique. Instantaneous velocity fields are measured with a 1K$\times$1K CCD camera adopting the frame straddle method while the concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. It is found that the general features of the mixing pattern are quite dependent on the local flow characteristics during the rapid decay of mean concentration. However, the small scale mixing seems to be independent on the local turbulent velocity fluctuation.

An Experimental Investigation of Air Fuel Ratio Measurement using Laser Induced Acetone Fluorescence (아세톤 형광을 이용한 공연비 측정 기법 연구)

  • Park Seungjae;Huh Hwanil;Oh Seungmook
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.353-356
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    • 2002
  • Planar laser induced fluorescence(PLIF) has been widely used to obtain two dimensional fuel distribution. Preliminary investigation was performed to measure quantitative air excess ratio distribution in an engine fueled with LPG. It is known that fluorescence signal from acetone as a fluorescent tracer is less sensitive to oxygen quenching than other dopants. Acetone was excited by KrF excimer laser (248nm) and its fluorescence image was acquired by ICCD camera with a cut-of filter to suppress Mie scattering from the laser light. For the purpose of quantifying PLIF signal, an image processing method including the correction of laser sheet beam profile was suggested. Raw images were divided by each intensity of laser energy and profile of laser sheet beam. Inhomogeneous fluorescence images scaled with the reference data, which was taken by a calibration process, were converted to air excess ratio distribution. This investigation showed instantaneous quantitative measurement of planar air excess ratio distribution for gaseous fuel.

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SPIV Flow Analysis of Turbulent Jet with Triangular Multi-Tabs (삼각형 멀티 탭이 부착된 난류제트에 대한 SPIV 유동해석 연구)

  • Jang Young Gil;Lee Sang Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.5 s.236
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    • pp.561-567
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    • 2005
  • The effect of triangular multi-tabs attached at the perimeter of jet nozzle on flow structure in the near field was investigated experimentally. A stereoscopic PIV(SPIV) system was employed to measure three orthogonal velocity components of the 3-D turbulent jet. In this study, two different types of sharp-edged jet nozzle having 4, 8 tabs were tested at the Reynolds number of Re=10,000. SPIV measurements were carried out at 5 cross-sectional planes. Six hundred instantaneous velocity fields were measured for each experimental condition and they were ensemble averaged to get spatial distributions of turbulent statistics such as mean velocity and turbulence intensity. Entrainment rate of surrounding fluid into the tabbed jets was estimated using the measured 3-D velocity field data. The strong vortex structure was induced for the jet flow with 4 tabs, increasing entrainment rate.

A Study on the Turbulent Characteristics of Rushton Turbine Mixer by Simultaneous Measurement of Velocity and Concentration Field with Stereo-PIV/PLIF Technique (Stereo-PIV/PLIF의 속도장과 농도장 동시측정 기법을 이용한 러쉬톤 교반기내 난류특성에 관한 연구)

  • Min, Young-Uk;Kim, Yun-Gi;Kim, Kyung-Chun
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.694-699
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    • 2003
  • Simultaneous measurement with PLIF(Planar Laser-Induced Fluorescence) and Stereo-PIV(Stereoscopic Particle Image Velocimetry) was performed to investigate the structural characteristics of flow field in Rushton Turbine Mixer. Instantaneous 3D velocity fields are measured by two 2K ${\times}$ 2K CCD cameras focused on an object plane with the angular displacement methods while the concentration fields are obtained through the measurement of the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. Finally, the spatial structures of turbulent mixing around Rushton turbine were identified by the calculation of cross-correlation fields between the velocity and concentration field.

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Large Eddy Simulation of Flow and Heat Transfer in a Rotating Ribbed Channel (요철이 설치된 회전하는 채널 내부의 유동 및 열전달의 큰에디모사)

  • Ahn, Joon;Choi, Hae-Cheon;Lee, Joon-Sik
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.193-198
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    • 2003
  • A gas turbine blade has an internal cooling passage equipped with ribs, which can be modeled as a ribbed channel. We have studied a flow inside a ribbed channel using large eddy simulaton (LES) with a dynamic subgrid-scale model. The simulation results are compared with the experimental ones. The turbulence intensity and local heat transfer near the rib have not been well captured by the conventional Reynolds averaged Navier-Stokes simulation (RANS). However, these variables obtained by the present LES agree well with those from experiments. From the instantaneous velocity and temperature fields, we explain the mechanisms responsible for the local peaks in the heat transfer distribution along the channel wall. We have also investigated the effect of rotation on the flow and heat transfer in the ribbed channel.

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Model on the electro-magnetic characteristics of elastic ferromagnetic materials with vibrationg gap (탄성 고투자율 자성체의 공극진동에 따른 전자기 특성에 관한 모델)

  • 김대수;김왕곤;홍진웅
    • Electrical & Electronic Materials
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    • v.9 no.9
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    • pp.891-899
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    • 1996
  • A model for predicting the characteristics of elastic ferromagnetic materials having a moving gap was presented. Based on the model parameters concerning behavior of material, such as the instantaneous field intensity, attractive force between the poles, length of gap, and the induced current/ emf in the circuit can be determined from the numerical integrations of the governing equations derived. From the results of the model it is found that when dc emf is imposed on the circuit the current sharply rise and fall for very short duration then stabilize at extremely low level which depends mainly on elasticity, permeabilities and ratio of resistivity. Subsequently output emf is shown stabilized at constant value which depends on the previous parameters as well as the resistivity ratio of primary to secondary circuit after sufficient progress of time.

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The Near Field Structure of Initially Asymmetic Jets (비대칭분류의 노즐출구영역에서의 난류유동장 해석)

  • Kim, K.H.;Shin, J.K.;Lee, H.Y.
    • Journal of ILASS-Korea
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    • v.4 no.4
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    • pp.38-45
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    • 1999
  • The near field structure of round turbulent jets with initially asymmetric velocity distribution is investigated experimentally. Experiments were carried out using a constant temperature hot-wire anemometry system to measure streamwise velocity in the jets. The measurements were undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distribution of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stress. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend at the upstream of the exit. Three pipes were used for this study: A straight pipe, 90 and 160 degree-bended pipes. Therefore, at the upstream of the pipe exit, the secondary flow through the bend and the mean streamwise velocity distribution could be controlled by changing the curvature of pipes.

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Comb Bandwidth generating in Frequency-shifted Feedback Laser (주파수 이동 되먹임 레이저에서 발생하는 Comb의 대역폭)

  • 지명훈;황대석;김규식;이영우
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2002.11a
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    • pp.535-538
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    • 2002
  • We simulated Frequency-shifted feedback laser using AOM inside the cavity. We analyze instantaneous oscillation frequency at peak spectral intensity and Comb bandwidth of output spectrum from Wigner-Ville distribution of intracavity electric field. The Comb bandwidth is defined as the product of the saturation-broadened bandwidth and the total resonant modes contributing to FSF operation.

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A Study on Slot-opening Effect in Interior Permanent Magnet Motor (매입형 영구자석 전동기의 Slot-opening Effect에 관한 연구)

  • Fang, Liang;Kim, Sung-Il;Hong, Jung-Pyo
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1027-1028
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    • 2007
  • In this paper, the variation of air-gap field intensity caused by the slot-opening in interior permanent magnet (IPM) motor is investigated, which is for predicting the instantaneous magnetic field more preciously in analytical method further. It is different with the approach of dealing the slot-opening effect on the air-gap field distribution with the "relative permeance" function in surface permanent magnet (SPM) motor. The prediction of the air-gap field in IPM motor is much more complex than SPM motor. In this study, an approximate estimation method is adopted based on analyzing the changing of flux path in both the IPM rotor part and stator part, and in additional an analytical function defined as "relative pole-arc" is built. The finite element method(FEM) is used for confirming the slot-opening effect on the field prediction.

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Simultaneous Measurement of Velocity and Concentration Field in a Stirred Mixer Using PIV/LIF Techniqueut and POD Analysis (PIV/LIF에 의한 교반혼합기 유동의 난류 속도/농도장 측정 및 POD해석)

  • Jeong Eun-Ho;Yoon Sang-Youl;Kim Kyung-Chun
    • 한국가시화정보학회:학술대회논문집
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    • 2002.11a
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    • pp.101-104
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    • 2002
  • Simultaneous measurement of turbulent velocity and concentration field in a stirred mixer tank is carried out by using PIV/LIF technique. Instantaneous velocity fields are measured by a $1K\times1K$ CCD camera adopting the frame straddle method while the concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. It is found that the general features of the mixing pattern are quite dependent on the local flow characteristics during the rapid decay of mean concentration. However, the small scale mixing seems to be independent on the local turbulent velocity fluctuation.

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