• Title/Summary/Keyword: fluid flow velocity

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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
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    • 2006.08a
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    • pp.319-322
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    • 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.

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Mass transfer in cross-flow dialyzer with internal recycle

  • Yeh, Ho-Ming;Chen, Chien-Yu
    • Membrane and Water Treatment
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    • v.4 no.4
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    • pp.251-263
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    • 2013
  • The internal reflux effect on dialysis through the retentate phase of a countercurrently cross-flow rectangular module is investigated. Theoretical analysis of mass transfer in cross-flow devices with or without recycling is analogous to heat transfer in cross-flow heat exchangers. In contrast to a device without reflux, considerable mass transfer is achievable if cross-flow dialyzers are operated with reflux, which provides an increase in fluid velocity, resulting in a reduction in mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration operated under high reflux ratio.

Flow Behavior in a Rectangular Tunnel Opened and Closed at Both Sides Using CFD

  • Lee, Yong-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.3
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    • pp.368-377
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    • 2012
  • Most tunnel simulations have been focused on the thermal field and the critical velocity for suppression of hot back-layering flow in case of fire and on the characteristics of a tunnel fire in terms of the flame propagation and the toxic gas generation. In this paper, a comparative study of the flow characteristics of polluted air with no heat source in a tunnel model opened and closed at both end sides is implemented into a recognized CFD simulation code. The model is used to investigate the flow characteristics depending on the three different Reynolds numbers of 640, 1270 and 2120, which have been chosen by the flow velocities of 0.3, 0.6 and 1.0 m/s through the inlet. The results of this study have shown that the CFD predictive and experimental approaches are available in qualitatively studying the correlation of flow behaviors for a better tunnel design.

Application of Holographic Interferometry and 2-D PIV for HSC Convective Flow Diagnostics (Hele-Shaw Cell 내부의 열유동 해석을 위한 홀로그래픽 간섭계와 2차원 PIV의 적용)

  • Kim, Seok;Lee, Sang-Joon
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.682-687
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    • 2003
  • The variations of temperature and velocity fields in a Hele-Shaw convection cell (HSC) were investigated using a holographic interferometry and 2-D PIV system with varying Rayleigh number. To measure quasisteady changes of temperature field, two different measurement methods of holographic interferometry; double-exposure method and real-time method, were employed. In the double-exposure method, unwanted waves can be eliminated effectively using digital image processing technique and the reconstruction images are clear, but transient flow structure cannot be reconstructed clearly. On the other hand, transient convective flow can be reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noises, compared with the double-exposure method. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow structure at high Rayleigh numbers. The periodic flow pattern at high Rayleigh numbers obtained by the real-time holographic interferometer method is in a good agreement with the PIV results.

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Effects of Asymmetric Tip Clearance on Centrifugal Compressor Flow (비대칭 팁간극이 원심압축기의 유동에 미치는 영향)

  • Yoon, Yong-Sang;Song, Seung-Jin
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.533-541
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    • 2005
  • Compared to axial compressors, an analytical model capable of analyzing the flow in centrifugal compressor lacks because of the difficulty in governing equations for radial duct. Therefore, this paper presents a new model to predict flow field in a centrifugal compressor with a sinusoidal asymmetric tip clearance. To predict the 2 dimensional flow in the inlet and exit of the centrifugal compressor, the two flow fields are connected with compressor characteristic based on Moore-Greitzer model. Contrary to axial compressors, the nonuniformity of impeller exit pressure in centrifugal compressor decreases as flow coefficient decreases. In addition, that is sensitive to the slope of pressure rise by eccentricity. The maximum velocity exists right before the maximum tip clearance.

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Unsteady Flow Rate Measurement Based on Distributed Parameter Pipeline Model (분포정수계 관로모델을 이용한 비정상 유량계측)

  • Kim, Do-Tae;Hong, Sung-Tae
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.3
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    • pp.8-13
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    • 2008
  • The paper proposes a model-based measurement of unsteady flow rate by using distributed parameter pipeline model and the measured pressure values at two distant points along the pipeline. The distributed parameter model of hydraulic pipeline is applied with consideration of frequency dependent viscosity friction and unsteady velocity distribution at a cross section of a pipeline. By using the self-diagnostics functions of the measurement method, the validity is investigated by comparison with the measured and estimated pressure and flow rate wave forms at the halfway section on the pipeline. The results show good agreement between the estimated flow rate wave forms and theoretical those under unsteady laminar flow conditions. The method proposed here is useful in estimating unsteady flow rate through an arbitrary cross section in hydraulic pipeline and components without installing an instantaneous flowmeter.

An Experimental Study on the Flow at the Impeller Exit of a Centrifugal Pump (원심펌프의 회전차 출구 유동에 관한 실험적 연구)

  • Kang, Shin-Hyoung;Hong, Soon-Sam
    • 유체기계공업학회:학술대회논문집
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    • 1999.12a
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    • pp.234-241
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    • 1999
  • The flow at the impeller exit is important to validate engineering design and numerical analysis of pumps. However, it is not easy to measure the flow at the impeller exit and evaluate the impeller performance since there is usually strong interaction between the impeller and the volute casing. We installed axisymmetric collector instead of the volute casing, so there is no interaction between the impeller and casing. A 3-hole Cobra probe is used to investigate the flow at impeller exit and vaneless diffuser region for design and on design flow rate. For a single suction centrifugal pump of low specific speed, the flow field such as velocity, flow angle, and total pressure are measured by traversing the probe across the vaneless diffuser. These data can be used for performance prediction, desist and numerical analysis of pumps.

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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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Performance Analysis of Francis Turbines by CFD (CFD을 이용한 프란시스 수차의 내부유동 해석)

  • Choi, Hyen-Jun;Hwang, Young-Cheol;Kim, You-Taek;Nam, Chung-Do;Lee, Young-Ho
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.06a
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    • pp.191.2-191.2
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    • 2010
  • The conventional method to assess turbine performance is its model testing which becomes costly and time consuming for several design alternatives in design optimization. Computational fluid dynamics (CFD) has become a cost effective tool for predicting detailed flow information in turbine space to enable the selection of best design. In the present paper, Francis turbine of commercial small hydropower plants which is under 70kw is investigated. Solutions are investigated with respect to the hydraulic characteristics against an outward angle of guide vane, the number of guide vane and head (inlet velocity). By suitable modification of the runner shape, low pressure zone on the leading edge can be reduced. If the entire runner is to be optimized in this manner, flow simulation tests have to be carried out on a series of different geometrical shape.

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Numerical Simulation of Plate Finned-Tubes Evaporator (평판핀이 부착된 증발기의 시뮬레이션)

  • Son, B.J.;Min, M.S.;Choi, S.G.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.1 no.4
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    • pp.297-304
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    • 1989
  • Development of a more satisfactory program of computing the performance on a multi-tube evaporator with continuous plate fins is attempted in this study. The fluid flow involving a change of phase make the flow properties and fluid friction factor of refrigerants, the heat transfer coefficients of refrigerant and air sides vary significantly. Taking such variations into account, a useful program is developed to predict the steady state performance of a multi-tube evaporator. The program was applied to an evaporator which has outside diameter of 10.05mm, inside diameter of 9.35mm, length of 5.4m and two rows arraied staggered. Then the variations of refrigerant quality, temperature, pressure, velocity, enthalpy, specific volume and air temperature, tube temperature were discussed. Satisfactory results were presented that the degree of superheat at the outlet side was $4.4^{\circ}C$ and the air temperature drop between the inlet and outlet of the air conditioner was $10^{\circ}C$.

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