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Research Papers: Fundamental Issues and Canonical Flows

A Study on Flow Transition and Development in Circular and Rectangular Ducts

[+] Author and Article Information
E.-S. Zanoun, C. Egbers

Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus, Siemens-Halske-Ring 14, D-03046 Cottbus, Germany

M. Kito

 Mie University, 1577 Kurimamachiya-cho, Tsu City, Mie Prefecture, Japan

J. Fluids Eng 131(6), 061204 (May 14, 2009) (10 pages) doi:10.1115/1.3112384 History: Received February 27, 2008; Revised February 17, 2009; Published May 14, 2009

The present paper reports observations on some aspects regarding the dependence of the transition Reynolds number and flow development on the inlet flow conditions and the entrance length in circular and rectangular ducts for Rem106×103, where Rem is the Reynolds number based on the bulk flow velocity (U¯b) and the duct integral length scale (D). The hot-wire anemometer was used to carry out measurements close to the circular duct exit; however, the laser-Doppler anemometry was utilized for the rectangular duct measurements. Particular considerations were given to the bulk flow velocity, the mean-velocity profile, the centerline-average-velocity, and the centerline turbulence statistics to the fourth order. Transition criteria in both ducts were discussed, reflecting effects of flow geometry, entrance flow conditions, and entrance length on the transition Reynolds number. A laminar behavior was maintained up to Rem15.4×103 and Rem2×103 in the circular and rectangular ducts, respectively, and the transition was observed to take place at different downstream positions as the inlet flow velocity varied.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Some selected samples of the streamwise traces from the hot-wire anemometer, located at the pipe centerline, for various inlet flow velocities and streamwise locations

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Figure 2

(a) Photograph of the current pipe test section and (b) summary of the L/D versus the mean-based Reynolds number, Rem, from some existing and planned pipe facilities

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Figure 3

Schematic of the experimental test facility

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Figure 4

The turbulence intensity level (u′/U¯) versus the bulk-velocity based Reynolds number (Rem) at the contraction exit without triggering the flow

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Figure 5

The present pipe centerline turbulence statistics (uc′/U¯c, Sc(u′), and Fc(u′)) versus x/D for 3×104≤Rec≤8×104(2.63×104≤Rem≤7×104) and 0% tripping

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Figure 6

The channel centerline turbulence statistics (uc′/U¯c, Sc(u′), and Fc(u′)) versus x/D for Rem=104 and 20% tripping (24)

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Figure 7

The ratio of the centerline-average-velocity (U¯c) to the bulk flow velocity (U¯b) versus the centerline-average-velocity and/or the bulk-velocity based Reynolds numbers in the pipe flow for various measuring locations (x/D)

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Figure 8

The ratio of the centerline-average-velocity (U¯c) to the bulk flow velocity (U¯b) versus the centerline-average-velocity based Reynolds number in the channel flow for various tripping ratios (24)

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Figure 9

The inner scaling of the present pipe mean-velocity profiles for 1040≤R+≤1140

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Figure 10

The inner scaling of the channel mean-velocity profiles for 118≤R+≤481(24)

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Figure 11

The present pipe normalized centerline-velocity fluctuations (uc′/U¯c) for various x/D versus the centerline-average-velocity and/or the bulk-velocity based Reynolds numbers

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Figure 12

The channel normalized centerline-velocity fluctuations (uc′/U¯c) for 0% and 10% tripping versus the centerline-average-velocity based Reynolds number (24)

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Figure 13

The present pipe centerline-velocity fluctuations (uc′2) for various x/D versus the centerline-average-velocity and/or the bulk-velocity based Reynolds numbers

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Figure 14

The channel centerline-velocity fluctuations (uc′2) for different tripping ratios versus the centerline-average-velocity based Reynolds number (24)

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Figure 15

The present pipe centerline skewness factor for various x/D versus the centerline-average-velocity and/or the bulk-velocity based Reynolds numbers

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Figure 16

The channel centerline skewness factor for different tripping ratios versus the centerline-average-velocity based Reynolds number (24)

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Figure 17

The present pipe centerline flatness factor for various x/D versus the centerline-average-velocity and/or the bulk-velocity based Reynolds numbers

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Figure 18

The channel centerline flatness factor for different tripping ratios versus the centerline-average-velocity based Reynolds number (24)

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