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Research Papers: Fundamental Issues and Canonical Flows

Investigations of Tripping Effect on the Friction Factor in Turbulent Pipe Flows

[+] Author and Article Information
A. Al-Salaymeh

Department of Mechanical Engineering, Faculty of Engineering and Technology, University of Jordan, Amman 11942, Jordansalaymeh@ju.edu.jo

O. A. Bayoumi

LSTM-Erlangen, Institute of Fluid Mechanics, Friedrich Alexander Universität Erlangen-Nürnberg, Cauerstrasse 4, D-91058 Erlangen, Germanyossammah@gmail.com

J. Fluids Eng 131(7), 071202 (Jun 16, 2009) (10 pages) doi:10.1115/1.3153364 History: Received August 12, 2007; Revised April 19, 2009; Published June 16, 2009

Tripping devices are usually installed at the entrance of laboratory-scale pipe test sections to obtain a fully developed turbulent flow sooner. The tripping of laminar flow to induce turbulence can be carried out in different ways, such as using cylindrical wires, sand papers, well-organized tape elements, fences, etc. Claims of tripping effects have been made since the classical experiments of Nikuradse (1932, Gesetzmässigkeit der turbulenten Strömung in glatten Rohren, Forschungsheft 356, Ausgabe B, Vol. 3, VDI-Verlag, Berlin), which covered a significant range of Reynolds numbers. Nikuradse’s data have become the metric by which theories are established and have also been the subject of intense scrutiny. Several subsequent experiments reported friction factors as much as 5% lower than those measured by Nikuradse, and the authors of those reports attributed the difference to tripping effects, e.g., work of Durst (2003, “Investigation of the Mean-Flow Scaling and Tripping Effect on Fully Developed Turbulent Pipe Flow,” J. Hydrodynam., 15(1), pp. 14–22). In the present study, measurements with and without ring tripping devices of different blocking areas of 10%, 20%, 30%, and 40% have been carried out to determine the effect of entrance condition on the developing flow field in pipes. Along with pressure drop measurements to compute the skin friction, both the Pitot tube and hot-wire anemometry measurements have been used to accurately determine the mean velocity profile over the working test section at different Reynolds numbers based on the mean velocity and pipe diameter in the range of 1.0×1054.5×105. The results we obtained suggest that the tripping technique has an insignificant effect on the wall friction factor, in agreement with Nikuradse’s original data.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sketch of the pipe flow test section showing the pipe entrance with tripping device and measuring test section

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Figure 2

Schematic of the pipe flow test setup showing the plenum chamber, measuring test section and the pressure taps at different pipe positions

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Figure 3

Pressure gradient distribution along part of the pipe test section at different Reynolds numbers

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Figure 4

The streamwise pressure gradient, dp/dx, as a function of the mean-based Reynolds number, Remean

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Figure 5

Pipe wall skin friction coefficient, cf, as a function of the mean-based Reynolds number, Remean

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Figure 6

Pipe Darcy friction factor, λ, as a function of the friction-velocity Reynolds number

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Figure 7

Pipe Darcy friction factor, λ, for the present nontripping measurements over an intermediate range of Reynolds numbers compared with Nikuradse’s data (14) and Zagarola and Smits (15)

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Figure 8

The streamwise pressure gradient, dp/dx, as a function of Reynolds numbers for tripping and nontripping conditions

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Figure 9

Turbulence Intensity versus Reynolds number for tripping and no-tripping conditions

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Figure 10

Pipe mean flow velocity (a) and centerline flow velocity (b) versus Reynolds number for tripping and nontripping conditions

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Figure 11

Pipe Darcy friction factor versus Reynolds number based on mean velocity for tripping cases compared with Nikuradse’s data

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Figure 12

Pipe Darcy friction factor versus Reynolds number based on friction velocity compared with tripping results

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Figure 13

The wall friction coefficient versus Reynolds number based on friction velocity compared with tripping results

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Figure 14

The present wall friction coefficient versus friction-velocity Reynolds number compared with Zagarola and Smits (15) results

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Figure 15

The normalized mean velocity distribution as a function of the normalized channel height at different values of Reynolds numbers for both data of the present measurements and the data of Zagarola and Smits

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Figure 16

The present mean velocity distribution for no tripping and 10% tripping conditions compared with the data of Zagarola and Smits at (a) Re=409,290 and (b) Re=309,500

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