Quantitative Visualization of a Submerged Pseudoplastic Jet Using Particle Image Velocimetry

1995 ◽  
Vol 117 (3) ◽  
pp. 369-373 ◽  
Author(s):  
A. Shekarriz ◽  
J. R. Phillips ◽  
T. D. Weir
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Nozzle Exit ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Image Velocimetry ◽  
Close Observation ◽  
Quantitative Visualization ◽  
Nozzle Exit Velocity

A preliminary experimental study of a pseudoplastic jet flow is reported in this paper. The velocity field was measured using Particle Image Velocimetry. Unlike a Newtonian jet, the pseudoplastic jet was observed to experience a sudden drop in its velocity at a reproducible position downstream of the nozzle for the range of velocities examined. This position moved downstream with an increase in the nozzle exit velocity. The center-line streamwise velocity decayed as X–15 to X–30 within the terminating region of the jet for three different nozzle exit velocities of 2.43, 3.17, and 5.42 m/s. This decay is in contrast to X–1 decay for a turbulent or laminar Newtonian jet. The location of the terminating region did not appear to scale with Reynolds number, Plasticity number, or Hedstrom number. At Reynolds numbers of 3000 and 6400, the instantaneous streamwise velocity maps indicated that the flow was fairly laminar, with a sinuous instability appearing at the higher Reynolds number condition. Close observation of the jet indicated that local turbulence could exist within regions of high shear rate. Further detailed study is required to confirm this observation.

Measurement of Velocity Profiles of Laminar to Turbulent Water Flows in a Tube Using Particle Image Velocimetry

2004 ◽  
Author(s):  
Meredith R. Martin
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Particle Image ◽  
Glass Tube ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Reynolds Number Flow ◽  
Image Velocimetry ◽  
Dye Visualization ◽  
Number Flow

The transition from laminar to turbulent in-tube flow is studied in this paper. Water flow in a glass tube with an inside diameter of 21.7 mm was investigated by two methods. First, a dye visualization test using a setup similar to the 1883 experiment of Osborne Reynolds was conducted. For the dye visualization, Reynolds numbers ranging from approximately 1000 to 3500 were tested and the transition from laminar to turbulent flow was observed between Reynolds numbers of 2500 and 3500. For the second method, a particle image velocimetry (PIV) system was used to measure the velocity profiles of flow in the same glass tube at Reynolds numbers ranging from approximately 500 to 9000. The resulting velocity profiles were compared to theoretical laminar profiles and empirical turbulent power-law profiles. Good agreement was found between the lower Reynolds number flow and the laminar profile, and between the higher Reynolds number flow and turbulent power-law profile. In between the flow appeared to be in a transition region and deviated some between the two profiles.

Particle Image Velocimetry Investigation of the Coherent Structures in a Leading-Edge Slat Flow

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Patrick R. Richard ◽  
Stephen John Wilkins ◽  
Joseph W. Hall
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Shear Layer ◽  
Coherent Structures ◽  
Particle Image ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Image Velocimetry ◽  
Lower Reynolds Number ◽  
Number Case

Air traffic volume is expected to triple in the U.S. and Europe by 2025, and as a result, the aerospace industry is facing stricter noise regulations. Apart from the engines, one of the significant contributors of aircraft noise is the deployment of high-lift devices, like leading-edge slats. The unsteady turbulent flow over a leading-edge slat is studied herein. In particular, particle image velocimetry (PIV) measurements were performed on a scale-model wing equipped with a leading-edge slat in the H.J. Irving–J.C.C. Picot Wind Tunnel. Two Reynolds numbers based on wing chord were studied: Re = 6 × 105 and 1.3 × 106. A snapshot proper orthogonal decomposition (POD) analysis indicated that differences in the time-averaged statistics between the two Reynolds numbers were tied to differences in the coherent structures formed in the slat cove shear layer. In particular, the lower Reynolds number flow seemed to be dominated by a large-scale vortex formed in the slat cove that was related to the unsteady flapping and subsequent impingement of the shear layer onto the underside of the slat. A train of smaller, more regular vortices was detected for the larger Reynolds number case, which seemed to cause the shear layer to be less curved and impinge closer to the tail of the slat than for the lower Reynolds number case. The smaller structures are consistent with Rossiter modes being excited within the slat cove. The impingement of the shear layers on and the proximity of the vortices to the slat and the main wing are expected to be strong acoustic dipoles in both cases.

A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge

2000 ◽  
Vol 214 (5) ◽  
pp. 655-671 ◽  
Author(s):  
S C M Yu ◽  
J B Zhao
Keyword(s):  
Particle Image Velocimetry ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Flow Condition ◽  
Particle Image ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Flow Conditions ◽  
Image Velocimetry

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.

Aerothermal Characterization of a Rotating Ribbed Channel at Engine Representative Conditions—Part I: High-Resolution Particle Image Velocimetry Measurements

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Ignacio Mayo ◽  
Gian Luca Gori ◽  
Aude Lahalle ◽  
Tony Arts
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Cross Section ◽  
Turbulence Intensity ◽  
Particle Image ◽  
Channel Cross Section ◽  
Recirculation Bubble ◽  
Rotation Numbers ◽  
Image Velocimetry ◽  
Static Conditions

The present work is part of a detailed aerothermal investigation in a model of a rotating internal cooling channel performed in a novel facility setup which allows test conditions at high rotation numbers (Ro). The test section is mounted on a rotating frame with all the required instrumentation, resulting in a high spatial resolution and accuracy. The channel has a cross section with an aspect ratio of 0.9 and a ribbed wall with eight ribs perpendicular to the main flow direction. The blockage of the ribs is 10% of the channel cross section, whereas the rib pitch-to-height ratio is 10. In this first part of the paper, the flow over the wall region between the sixth and seventh ribs in the symmetry plane is investigated by means of two-dimensional particle image velocimetry (PIV). Tests were carried out at a Reynolds number (Re) of 15,000 in static and rotating conditions, with a maximum Ro of 0.77. Results are in good agreement with the data present in literature at the same Reynolds number and with rotation numbers of 0 (static conditions) and 0.38 in a channel with the same geometry as in the present work. When Ro is increased from 0.38 to 0.77, the main velocity and turbulence fields show important changes. At a rotation number of 0.77, although the extension of the recirculation bubble after the sixth rib on the trailing side does not vary significantly, it covers the full inter-rib area on the leading side in the streamwise direction. The turbulence intensity on the leading side shows a low value with respect to the static case but roughly at the same level as in the lower Ro case. On the trailing side, the maximum value of the turbulence intensity slightly decreases from Ro  = 0.38 to Ro  = 0.77, the wall shear layer is restabilized along the second half of the pitch due to the high rotation, and the secondary flows are redistributed causing spanwise vortex compression. The observed result is the rapid decay of turbulent fluctuations in the second half of the inter-rib area.

Water Synthetic Jet Driven by a Piezoelectric Actuator – LIF and PIV Experiments

2015 ◽  
Vol 1104 ◽  
pp. 45-50 ◽  
Author(s):  
Zuzana Broučková ◽  
Shu Shen Hsu ◽  
An Bang Wang ◽  
Zdeněk Trávníček
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Piezoelectric Actuator ◽  
Particle Image ◽  
Three Dimensional ◽  
Laser Induced Fluorescence ◽  
Synthetic Jet ◽  
Fluid Exchange ◽  
Image Velocimetry ◽  
Surrounding Fluid

A synthetic jet (SJ) is a fluid jet flow generated from fluid oscillations during a periodical fluid exchange between an actuator cavity and surrounding fluid. A water synthetic jet was generated from submerged piezoelectric-driven SJ actuator. The actuator slot width was 0.36 mm. The experiments were performed using laser induced fluorescence (LIF) flow visualization and particle image velocimetry (PIV) techniques, both in a phase locked setup. The LIF visualization was used to demonstrate three-dimensional nature of the SJ formation process and to estimate SJ velocity. The PIV experiment quantified SJ velocity cycles in chosen plans. The driven frequency was adjusted near the resonance at approximately 46 Hz. It was evaluated theoretically and confirmed experimentally by means of LIF visualization. The time-mean orifice velocity and the Reynolds number were estimated asU0= 0.07–0.10 m/s andRe= 100–150, respectively.

scholarly journals The PIV study of air flow past the counter-swirler 53983

2018 ◽  
Vol 168 ◽  
pp. 05004 ◽  
Author(s):  
Daniel Duda
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Shear Layer ◽  
Particle Image ◽  
Contact Region ◽  
Air Flow ◽  
Swirling Jets ◽  
Flow Past ◽  
Image Velocimetry ◽  
Band Pass

PIV (particle image velocimetry) measurement of the air flow past a counter-swirler 53983 (anticlockwise swirler surrounded by clockwise swirler) is performed. The measurement is focused to an area at the boundary between the inner swirling jet and the outer one rotating oppositely. The Reynolds number Re based on the inner swirler diameter ranged form 1.2·103 to 2.1·104. By using band pass filtering the shear layer and vortices in the contact region between counter-swirling jets is highlighted. The shear layer between these regions shortens and decays into vortices as Reynolds number increases.

A Flow Study of Pulsed Jet Cross-Flow Interaction by Micro Particle Image Velocimetry

2006 ◽  
Author(s):  
Kenichi Watanabe ◽  
Tomonori Nakatsuka ◽  
Daichi Suzuki ◽  
Takashi Nagumo ◽  
Masahiro Motosuke ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Flow Control ◽  
Particle Image ◽  
Low Reynolds Number ◽  
Cross Flow ◽  
Synthetic Jet ◽  
Pulsed Jet ◽  
Micro Particle Image Velocimetry ◽  
Image Velocimetry

Recent development of micro devices is remarkable as in the examples of Micro-TAS, Lab-on-a-chip or ultra micro gas turbine. In order to make the micro devices smaller and more effective, an appropriate use of a micro scale jet as an actuator can be a key technology. Aiming at the development of a measurement system of the micro flow control devices in the future micro aerodynamics, we have established a system to measure a continuous jet, a pulsed jet and a synthetic jet for the flow control in the low Reynolds number air flow with a micro length scale. The two-dimensional flow field around the micro jet using micro particle image velocimetry (PIV) was measured. The jet was injected through the device using an acoustic speaker. It was observed that a saddle point existed at the certain phase where the velocity is 0 at the boundary of the jet blowing and suction phase for the synthetic jet into a still air. It was found that the pulsed jet and the synthetic jet are more effective in the fluid mixing in the low Reynolds number flow than the continuous jet. The dead water region was observed downstream of the jet in case of the jet injection into cross flow. It was recognized that the synthetic jet at the certain oscillation frequency generated a vortex pair near the jet hole.

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