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TECHNICAL PAPERS

Velocity and Pressure Measurements Along a Row of Confined Cylinders

[+] Author and Article Information
Barton L. Smith, Jack J. Stepan

Mechanical and Aerospace Engineering, Utah State University, Logan, Utah 84322

Donald M. McEligot

 Idaho National Laboratory (INL), Idaho Falls, Idaho 83415-3885; University of Arizona, Tucson, Arizona 85721; IKE,  University of Stuttgart, D-70569 Stuttgart, Deutschland

J. Fluids Eng 129(10), 1314-1327 (Mar 02, 2007) (14 pages) doi:10.1115/1.2776970 History: Received August 01, 2006; Revised March 02, 2007

The results of flow experiments performed in a row of confined cylinders designed to mimic a model of a prismatic gas-cooled reactor lower plenum design are presented. Pressure measurements between the cylinders were made. Additionally, the flow field was measured using particle image velocimetry at two different resolutions (one at high resolution and a second with wide angle that includes three cylinders). Based on these measurements, five regimes of flow behavior are identified that are found to depend on Reynolds number. It is found that the recirculation region behind the cylinders is shorter than that of half-cylinders placed on the wall representing the symmetry plane. Unlike a single cylinder, the separation point is always found to be on the rear of the cylinders, even at very low Reynolds number.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

The test section used in this study. Air enters through screens at the left, into a contraction and into the test section. The field of view for the wide-angle PIV data is shown (i.e., the laser sheet). The laser sheet moves through the near transparent side of the facility and terminates on the opaque far side. Streamwise locations of the pressure taps are indicated with arrows on the top wall. These taps are in the spanwise center of the channel. A second view of the facility is shown in Fig. 3.

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Figure 2

A sample PIV raw-data image. No masking or other processing has been performed. The laser sheet enters from below. The edges of the wall cylinders are visible in all four corners of the image. The center cylinder generates a shadow on the far wall. An additional region around the cylinder is dark due to the effects explained in conjunction with Fig. 3.

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Figure 3

A schematic diagram showing the cause of the dark region near the cylinder surface for the wide-angle data. The camera’s view of the surface is blocked by the near end of the cylinder. The end of the cylinder is not visible in the images since it is not illuminated.

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Figure 4

Instantaneous velocity vectors normalized by Uav

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Figure 5

Instantaneous velocity vectors normalized by Uav

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Figure 6

Pressure losses represented by minor loss factors. Data for equilateral triangle arrays from Žukauskas (5) with P∕D=1.5 and 2.0 and Bergelin (12) with P∕D=1.25 and 1.5 are also included.

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Figure 13

Definition of the separation angle θ, wake length Lw, and recirculation length Lc. Streamlines are for flow at Re=237.

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Figure 14

Measures of the wake length relative to the diameter as a function of Reynolds number for the centerline cylinder and for the half-cylinder on the lower wall. Data from Moulinec (30) and Balachandar (37) are also shown for reference.

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Figure 15

The high-resolution data domains. The dimensions of each field of view are shown at top right. Three fields of view were acquired at each Reynolds number.

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Figure 16

Example of instantaneous vector field for Re=2621. We note that the plot is a composite of two different fields of view that were acquired at different times.

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Figure 17

Instantaneous vector field for Re=15,075. We note that the plot is a composite of two different fields of view that were acquired at different times.

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Figure 18

The time-averaged contours of velocity magnitude (top left, increment is 0.2), Reynolds shear stress u′v′¯∕Uave2 (bottom left, increment is 0.005), relative streamwise rms level urms∕Uave (top right, increment is 0.05) and relative cross-stream rms level vrms∕Uav (bottom right, increment is 0.05) for Re=237.

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Figure 19

The time-averaged contours of velocity magnitude (top left, increment is 0.2), Reynolds shear stress u′v′¯∕Uave2 (bottom left, increment is 0.05), relative streamwise rms level urms∕Uave (top right, increment is 0.05), and relative cross-stream rms level vrms∕Uav (bottom right, increment is 0.05) for Re=507.

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Figure 20

The time-averaged contours of velocity magnitude (top left, increment is 0.2), Reynolds shear stress u′v′¯∕Uave2 (bottom left, increment is 0.05), relative streamwise rms level urms∕Uave (top right, increment is 0.05) and relative cross-stream rms level vrms∕Uave (bottom right, increment is 0.05) for Re=1135

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Figure 21

The time-averaged contours of velocity magnitude (top left, increment is 0.2), Reynolds shear stress u′v′¯∕Uave2 (bottom left, increment is 0.05), relative streamwise rms level urms∕Uave (top right, increment is 0.05) and relative cross-stream rms level vrms∕Uave (bottom right, increment is 0.05) for Re=2621.

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Figure 22

The time-averaged contours of velocity magnitude (top left, increment is 0.2), Reynolds shear stress u′v′¯∕Uave2 (bottom left, increment is 0.05), relative streamwise rms level urms∕Uave (top right, increment is 0.05), and relative cross-stream rms level vrms∕Uave (bottom right, increment is 0.05) for Re=15,075

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Figure 23

The time-averaged contours of velocity magnitude (top left, increment is 0.2), Reynolds shear stress u′v′¯∕Uave2 (bottom left, increment is 0.05), relative streamwise rms level urms∕Uave (top right, increment is 0.05), and relative cross-stream rms level vrms∕Uave (bottom right, increment is 0.05) for Re=55,920

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Figure 24

Radial profiles of Uθ at θ=90deg for several values of Re above (closed symbols) and below (open symbols) the apparent boundary layer transition to turbulence

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Figure 25

The angle at which the time-averaged boundary layer separates. The fitted curve is used to provide separation points for wide-angle cases.

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Figure 12

Cross-stream profiles of the Reynolds shear stress u′v′¯∕Uav2 halfway between the fourth cylinder and the next half-cylinders (as indicated in Fig. 1). Every third data point is shown. Symbols as in Fig. 8.

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Figure 11

Cross-stream profiles of the cross-stream Reynolds normal stress v′v′¯∕Uav2 halfway between the fourth cylinder and the following half-cylinders (as indicated in Fig. 1). Every third data point is shown. Symbols as in Fig. 8.

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Figure 10

Cross-stream profiles of the streamwise Reynolds normal stress u′u′¯∕Uav2 halfway between the fourth cylinder and the following half-cylinders (as indicated in Fig. 1). Every third data point is shown. Symbols as in Fig. 8.

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Figure 9

Cross-stream profiles of the mean cross-stream velocity for a range of Reynolds numbers halfway between the fourth cylinder and the following half-cylinders (as indicated in Fig. 1). Every third data point is shown. Symbols as in Fig. 8.

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Figure 8

Cross-stream profiles of the mean streamwise velocity for a range of Reynolds numbers halfway between the fourth cylinder and the following half-cylinders (as indicated in Fig. 1). Every third data point is shown.

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Figure 7

Pressure drop coefficient Cp=ΔP∕(1∕2ρUmax2) in between taps for several values of Reynolds number

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