PIV Measurement of Separated Flow in a Square Channel With Streamwise Periodic Ribs on One Wall

[+] Author and Article Information
Lei Wang

Heat Transfer Division, Lund University, Box 118, SE-221 00, Lund, Sweden

Jiri Hejcik

Faculty of Mechanical Engineering, Brno University of Technology, 616 69, Brno, Czech Republic

Bengt Sunden1

Heat Transfer Division, Lund University, Box 118, SE-221 00, Lund, SwedenBengt.Sunden@vok.lth.se


Corresponding author.

J. Fluids Eng 129(7), 834-841 (Jan 04, 2007) (8 pages) doi:10.1115/1.2742723 History: Received March 17, 2006; Revised January 04, 2007

In this study, particle image velocimetry (PIV) is used to investigate the physical process of separated flow in a square channel roughened with periodically transverse ribs on one wall. The ribs obstruct the channel by 15% of its height and are arranged 12 rib heights apart. The Reynolds number, based on the bulk-mean velocity and the corresponding hydraulic diameter of the channel, is fixed at 22,000. Assuming flow periodicity in the streamwise direction, the investigated domain is between two consecutive ribs. The emphasis of this study is to give some insight into the turbulence mechanism associated with separation, reattachment, and subsequent redevelopment. Results are included for mean velocity, friction coefficient, vorticity thickness, Reynolds shear stress, anisotropy parameter, and production of turbulent kinetic energy and shear stress. Based on the two-point correlation profiles, Taylor microscales are derived to reveal the sizes of the turbulence structure in the longitudinal and lateral directions. Moreover, Galilean decomposition is applied to the instantaneous velocity fields. The result shows that the separated shear layer is dominated by the large-scale, unsteady vortical structures.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Sketch of experimental setup

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Figure 2

Rib configuration and measurement planes: (a) vertical symmetry plane and (b) horizontal plane

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Figure 3

Streamlines of the mean flow

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Figure 4

Skin-friction coefficient along the ribbed wall

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Figure 5

Mean streamwise velocity profiles

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Figure 6

Mean vertical velocity at y∕e=1.1

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Figure 7

Visualization of vortices; the reference frame velocity is Uf=5.0m∕s(0.52Ur)

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Figure 8

Visualization of vortices; the reference frame velocity is Uf=3.7m∕s(0.38Ur)

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Figure 9

Vorticity thickness growth along the separated shear layer

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Figure 10

Reynolds shear stress profiles

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Figure 11

Maximum shear stress distribution

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Figure 12

Anisotropy parameter

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Figure 13

Turbulent kinetic energy production

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Figure 14

Reynolds shear stress production

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Figure 15

Spanwise u′ correlation coefficient at different points (x∕e,y∕e) in the flow field: A (0.5, 1), B (5.5, 2), C (5.5, 1), and D (8, 1)

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Figure 16

Streamwise u′ correlation coefficient

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Figure 17

Streamwise w′correlation coefficient

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Figure 18

Mean velocity vector plot near the ribbed wall

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Figure 19

Mean reattachment length in the spanwise direction




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