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Research Papers: Fundamental Issues and Canonical Flows

Experiments on Bounded Vortex Flows and Related Particle Transport

[+] Author and Article Information
Y. Huang, J. S. Marshall

e-mail: jeffm@cems.uvm.edu School of Engineering, University of Vermont, Burlington, Vermont 05405

J. Fluids Eng 133(7), 071204 (Jul 22, 2011) (9 pages) doi:10.1115/1.4004453 History: Received December 14, 2010; Revised June 17, 2011; Published July 22, 2011; Online July 22, 2011

The flow field generated by the combination of a downward-oriented annular slot jet with a circumferential velocity component and a suction port in the space between two horizontal planes is referred to as a bounded vortex flow. The current paper reports on an experimental study of the flow field and its ability to transport particles. Particle image velocimetry measurement shows that the ratio of the inlet to outlet flow rate and the ratio of the plate separation distance to the jet inlet radius control the wall-normal vortex strength and entrainment of the jet into the suction port. A toroidal vortex ring was also observed to form in certain cases. In particle experiments a separatrix curve is observed beyond which particles roll outward and within which particles roll inward; thus forming a cleaned region with radius that decreases with increase in the flow rate ratio.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Computational results for a bounded vortex flow showing the annular jet inlet at the top and the wall-normal vortex at the center. The shaded surface is an iso-vorticity magnitude surface and the lines are streamlines introduced at the jet inlet. (From Maynard [22] with permission.)

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Figure 2

Schematic of the experimental apparatus, showing (1) the nozzle, (2) the impingement surface, (3) the vacuum, (4) the nitrogen tank, (5) the fluidized-bed particle seeder, (6) the flow meter, (7) the differential pressure gauge, (8) the pressure gauge, and (9) the control valves

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Figure 3

Closeup showing (a) the nozzle interior design and (b) the nozzle viewed from the bottom. In (b) the circle at the center denotes the suction port and the ring surrounding this circle denotes the annular jet inlet.

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Figure 4

Contour plots of dimensionless velocity magnitude in the x-z plane obtained from PIV experiments for cases with h = 1.3 and (a) η = 0.5, (b) 1, (c) 2, and (d) 3

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Figure 5

Velocity streamlines in x-z plane obtained from PIV experiments for cases with h = 1.3 and (a) η = 0.5, (b) 1, (c) 2, and (d) 3

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Figure 6

Plots of dimensionless wall-normal vortex strength (Γ) versus dimensionless distance (z) from the impingement plate obtained from PIV experiments for spacing ratio h = 1.3. Plots are given for flow rate ratios η=0.5 (squares), 1 (triangles), 2 (diamonds), and 3 (circles). Lines are drawn connecting experimental data points for a given flow rate ratio. Uncertainty in vortex strength is approximately ± 10%.

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Figure 7

Profiles of the dimensionless azimuthal velocity obtained from PIV experiments with h = 1.3, for cases (from top to bottom) with η = 0.5 (dashed line), 1 (solid line), and 2 (dashed-dotted line). Velocity is measured at a dimensionless elevation z=0.13 above the impingement surface. Uncertainty in azimuthal velocity averages ±13% of the peak value.

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Figure 8

Critical jet inlet flow rate required to initiate motion of particles with H = 10 mm confinement height as a function of vacuum outlet flow rate. The data are indicated by symbols, and a best-fit third order polynomial curve is shown as a dashed line.

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Figure 9

Time sequence of photos (taken from below the impingement plate) for case A2 showing removal of particles from the plate following an impulsive start. Pictures are given for dimensionless times (from left to right starting with top row) t = 0, 226, 310, 396, 961, 2233, 3081, 4777.

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Figure 10

Final image at long time of particles for (a) case A1, (b) case A2, and (c) case A3. The dotted circle indicates the location of the vacuum outlet and the dashed circle is the mean jet position.

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Figure 11

Time sequence of photos (taken from below the impingement plate) for case B2 showing removal of particles from the plate following an impulsive start. Pictures are given for dimensionless times (from left to right starting with top row) t = 0, 28, 57, 85, 113, 141.

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Figure 12

Final image at long time of particles for (a) case B1, (b) case B2, (c) case B3, and (d) case B4. The dotted circle indicates the location of the vacuum outlet and the dashed circle is the mean jet position. In cases B2–B4, particles remain at the nozzle center after long time.

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Figure 13

Plots showing (a) radius Rclean of cleaned region as a function of jet inlet flow rate Qin and (b) dimensionless radius rclean of cleaned region as a function of flow rate ratio η. Both plots are for separation distance H = 10 mm (or h=1.3), with vacuum flow rate Qout set equal to 33 (squares), 67 (circles), 103 (deltas), 133 (right triangles), 167 (diamonds), where all flow rates are in cm3 /s. Data uncertainty in the vertical axis is approximately ± 9%.

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Figure 14

Plots showing (a) radius Rclean of cleaned region as a function of jet inlet flow rate Qin and (b) dimensionless radius rclean of cleaned region as a function of flow rate ratio η. Both plots are for separation distance H = 2 mm (or h=0.27), with symbols having the same meaning as in Fig. 1. Data uncertainty in the vertical axis is approximately ± 9%.

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