• 제목/요약/키워드: Flow Measurements

검색결과 1,813건 처리시간 0.029초

Experimental characterization of the lateral and near-wake flow for the BARC configuration

  • Pasqualetto, Elena;Lunghi, Gianmarco;Rocchio, Benedetto;Mariotti, Alessandro;Salvetti, Maria Vittoria
    • Wind and Structures
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    • 제34권1호
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    • pp.101-113
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    • 2022
  • We experimentally investigate the high-Reynolds flow around a rectangular cylinder of aspect ratio 5:1. This configuration is the object of the international BARC benchmark. Wind tunnel tests have been carried out for the flow at zero angle of attack and a Reynolds number, based on the crossflow cylinder length and on the freestream velocity, equal, to 40 000. Velocity measurements are obtained by using hot-wire anemometry along 50 different cross-flow traverses on the cylinder side and in the near wake. Differential pressure measurements are acquired on multiple streamwise sections of the model. The obtained measurements are in a good agreement with the state-of-the-art experiments. For the first time among the several contributions to the BARC benchmark, detailed flow measurements are acquired in the region near the cylinder side and in the near-wake flow. The edges and the thickness of the shear layers detaching from the upstream edges are derived from velocity measurements. Furthermore, we compute the flow frequencies characterizing the roll-up of the shear layers, the evolution of vortical structures near the cylinder side and the vortex shedding in the wake.

유동 가시화와 LDV 측정을 이용한 흡기계 내의 유동장에 관한 실험적 해석 (An Experimental Analysis of the Flow Field in an Air Induction System by Flow Visualization and LDV Measurements)

  • 유성출
    • 한국자동차공학회논문집
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    • 제9권1호
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    • pp.102-111
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    • 2001
  • To describe the air flow characteristics within an air cleaner cover and mass air flow sensor (MAFS) entry region installed in a 3.0L engine air induction system, flow visualization, velocity and turbulence intensity measurements were taken in several view planes. A detailed knowledge of the interaction between the design parameters and the flow structures will enhance our understanding of the motions within the flow field and enable engineers to optimize the induction system and reduce the signal-to-noise ratio in the MAFS output. Emphasis is placed on the analysis of coherent motions and the controlling parameters which affect the air flow in the MAFS entrance region over a flow rate of 13-240 kg/hr. The high speed motion pictures illustrated that the air flow generated within the air cleaner cover under steady state condition is quite complex. In both axial and radial planes of the main passage it was found that the flow pattern is remarkably influenced by the air cleaner cover and main passage configuration. A comparison of the flow patterns and measurements in the original and modified air cleaner cover is presented. Measurements from the MAFS indicated an significant reduction in pressure drop and signal noise for the modified cover as compared with the original cover, over an air flow rate of 13-240 kg/hr.

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Experimental Study on the Mean Flow Characteristics of Forward-Curved Centrifugal Fans

  • Kwon, Eui-Yong;Cho, Nam-Hyo
    • Journal of Mechanical Science and Technology
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    • 제15권12호
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    • pp.1728-1738
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    • 2001
  • Measurements have been made in an automotive HVAC b1ower for two different centrifugal fans. This work is directed at improving the performance of a conventional forward-curved centrifugal fan for a given small blower casing. Mean velocities and pressure have been measured using a miniature five-hole probe and a pressure scanning unit connected to an online data acquisition system. First, we obtained the fan performance versus flow rates showing a significant attenuation of unstable nature achieved with the new fan rotor in the surging operation range. Second, aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage for different fan operating conditions. The measurements stowed that performance coefficients are strongly influenced by flow characteristics at the throat region. The main flow features ware common in both fans, but improved performance is achieved with tole new fan rotor, particularly in lower flow rate legions. Based on the measured results, design improvements were carried out in an acceptable operation range, which gave considerable insight into what features of flow behavior ware most important.

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Quantification of Volumetric In-Cylinder Flow of SI Engine Using 3-D Laser Doppler Velocimetry ( II )

  • Yoo, Seoung-Chool
    • 한국유체기계학회 논문집
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    • 제10권4호
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    • pp.47-54
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    • 2007
  • Simultaneous 3-D LDV measurements of the in-cylinder flows of three different engine setups were summarized for the quantification of the flow characteristics in each vertical or horizontal plane, and in entire cylinder volume. The ensemble averaged-velocity, tumble and swirl motions, and turbulent kinetic energy during the intake and compression strokes were examined from the measured velocity data (approximately 2,000 points for each engine setup). The better spatial resolution of the 3-D LDV allows measurements of the instantaneous flow structures, yielding more valuable information about the smaller flow structures and the cycle-to-cycle variation of these flow patterns. Tumble and swirl ratios, and turbulent kinetic energy were quantified as planar and volumetric quantities. The measurements and calculation results were animated for the visualization of the flow, and hence ease to analysis.

A 6 m cube in an atmospheric boundary layer flow -Part 1. Full-scale and wind-tunnel results

  • Hoxey, R.P.;Richards, P.J.;Short, J.L.
    • Wind and Structures
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    • 제5권2_3_4호
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    • pp.165-176
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    • 2002
  • Results of measurements of surface pressure and of velocity field made on a full-scale 6 m cube in natural wind are reported. Comparisons are made with results from boundary-layer wind-tunnel studies reported in the literature. Two flow angles are reported; flow normal to a face of the cube (the $0^{\circ}$ case) and flow at $45^{\circ}$. In most comparisons, the spread of wind-tunnel results of pressure measurements spans the full-scale measurements. The exception to this is for the $0^{\circ}$ case where the roof and side-wall pressures at full-scale are more negative, and as a result of this the leeward wall pressures are also lower. The cause of this difference is postulated to be a Reynolds Number scale effect that affects flow reattachment. Measurements of velocity in the vicinity of the cube have been used to define the mean reattachment point on the roof centre line for the $0^{\circ}$ case, and the ground level reattachment point behind the cube for both $0^{\circ}$ and $45^{\circ}$ flow. Comparisons are reported with another full-scale experiment and also with wind-tunnel experiments that indicate a possible dependency on turbulence levels in the approach flow.

섬강시험유역의 유량측정에 대반 불확실도 해석 (Uncertainty Analysis of Flow Measurements of Seom River Experimental Watershed)

  • 최흥식;조민석;김상호;박정수
    • 한국관개배수논문집
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    • 제11권2호
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    • pp.47-54
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    • 2004
  • The flow measurements have been .carried out without the evaluation for data accuracy. For the reliable data acquisition, the experimental watershed has been operated and the uncertainty analysis for flow measurements and the developed rating curves are i

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압력측정을 이용한 과도기유량의 결정방법에 관한 연구 (A method for the determination of transient flow rates from pressure measurements)

  • 이성래
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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    • pp.724-729
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    • 1992
  • A transient hydraulic flow rate computation scheme is described here so that the transient hydraulic flow rate can be determined using the dynamic pressure measurements at the ends of a straight flowline with a dynamic, model of the hydraulic line. Simulation results indicate that the method is relatively robust to realistic levels of uncertainties in the fluid properties.

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토크 컨버터 내부 유동장 측정 (II) (Flow Field Measurements in a Torque Converter (II))

  • 유성출;장성국
    • 동력기계공학회지
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    • 제13권6호
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    • pp.82-87
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    • 2009
  • LDV measurements were conducted on the planes between impeller blades of torque converter. The flow fields are extremely complex because they contain unsteady viscous three-dimensional flows. Besides of their complexity, the difference in rotor speeds between the impeller and turbine compound the flow effects. The good spatial resolution of the LDV allows measurements of the instantaneous flow structures within the impeller passage, yielding valuable information about the production automotive torque converter in realistic operating conditions. It was found that the mass flow rates are strongly related with the internal flow characteristics of torque converter.

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5공 피토관 및 회전 열선 유속계에 의한 축류 홴 내부 유동장 계측 및 평가 (Flow Measurements and Performance Analysis using a 5-Hole Pitot Tube and a Rotating Hot-Wire Probe in an Axial Flow Fan)

  • 장춘만;김광용
    • 대한기계학회논문집B
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    • 제27권12호
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    • pp.1750-1757
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    • 2003
  • This paper describes the flow measurements inside the blade passage of an axial flow fan by using a rotating hot-wire probe sensor from a relative flame of reference fixed to the rotor blades. The validity of fan rotor designed by a streamline curvature equation was performed by the measurement of the three-dimensional flow upstream and downstream of the fan rotor using a 5-hole pitot tube. The vortical flow structure near the rotor tip can be clearly observed by the measurements of a relative velocity and its fluctuation on quasi-orthogonal planes to a tip leakage vortex. Larger vortical flow, which results in higher blockage in the main flow, is formed according to decrease a flow rate. The vortical flow spreads out to the 30 percent span from the rotor tip at near stall condition. In the design operating condition, the tip leakage vortex is moved downstream while the center of the vortex keeps constant in the spanwise direction. Detailed characteristics of a velocity fluctuation with relation to the vortex were also analyzed.

다위상 유체 속도 계측을 위한 영상기법 적용 (Multi-phase Flow Velocity Measurement Technique using Shadow Graphic Images)

  • 류용욱;정광효
    • 한국해양공학회지
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    • 제26권3호
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    • pp.61-65
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    • 2012
  • Air-water flow measurements are of importance for the coastal and ocean engineering fields. Although kinematic investigations of the multi-phase flows have been conducted for long time, velocity measurements still are concerned with many researchers and engineers in coastal and ocean areas. In the present study, an imaging technique using shadowgraphy and fiber optic probe for velocity measurements of air bubbles is introduced. The shadow graphy image technique is modified from the typical image velocimetry methods, and optical fibers are used for the well-known intrusive coupled phase-detection probe system. Since the imaging technique is a non-intrusive optical method from the air, it is usually applied for 2D flows. On the other hand, the double fiber optic probes touch flows regardless of flow patterns. The results of the flow measurements by both methods are compared and discussed. The methods are also applied to the measurements of overtopping flows by a breaking wave over the structure fixed on the free surface.