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Research Papers: Fundamental Issues and Canonical Flows

Steady and Pulsating Turbulent Flows in Complex Pipe Geometries

[+] Author and Article Information
Simone Colonia

Department of Mechanical
and Aerospace Engineering,
Università “La Sapienza”,
Via Eudossiana 18,
Roma 00184, Italy

Giovanni P. Romano

Department of Mechanical
and Aerospace Engineering,
Università “La Sapienza”,
Via Eudossiana 18,
Roma 00184, Italy
e-mail: giampaolo.romano@uniroma1.it

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received May 14, 2013; final manuscript received June 5, 2014; published online September 4, 2014. Assoc. Editor: Peter Vorobieff.

J. Fluids Eng 136(11), 111201 (Sep 04, 2014) (15 pages) Paper No: FE-13-1318; doi: 10.1115/1.4027825 History: Received May 14, 2013; Revised June 05, 2014

In this paper, measurements of velocity and stress fields in rigid pipes are performed by means of planar particle image velocimetry (PIV). The attention is focused onto the effect of Reynolds number and of continuous or pulsating flows by investigating pipe geometries ranging from the straight pipe to the reduced section and bifurcated ones. The obtained results show that, in the tested range, the effect of Reynolds number is limited for straight and reduced section pipes, while significant for the bifurcated one. Independently of Reynolds number, different geometries and forcing (continuous or pulsed) produce strong variations in intensity and spatial distribution of velocity and stress fields. Considering the latter, the contribution of viscous and turbulent stresses are measured separately and compared. Indeed turbulent stresses are always larger than the viscous ones, but the relative intensity is highly variable as also the spatial distribution of maxima and minima. Specifically, in the pulsating flows, this distribution is phase-dependent reflecting the oscillations of regions of flow separation which form especially in reduced section and bifurcated pipes. These results are useful for all engineering applications in which turbulent pipe flows are involved.

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Figures

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Fig. 1

The straight, reduced section and bifurcated pipes (made by Pyrex glass) used in the present experiments with characteristic size

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Fig. 2

The experimental setup for the continuous (at the top) and pulsatile flows (at the bottom). A photograph of the circular pipe inserted into the test section is given on the right.

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Fig. 3

The forcing piston position and velocity curves for the pulsatile conditions

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Fig. 4

Average vector field (at the top left), velocity profile comparisons (at the top right), and axial behavior of flow rate (at the bottom). Continuous flow in the straight pipe at two Reynolds numbers.

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Fig. 5

Average vector field (at the top left), velocity profile comparisons (at the top right), and axial behavior of centerline velocity (at the bottom). Continuous flow in the reduced section pipe at two Reynolds numbers and comparisons with data by Deshpande and Gibbons [19] at Re = 5000.

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Fig. 6

Average vector field (at the top) and axial behavior of flow rate in the two branches (at the bottom). Continuous flow in the bifurcated pipe at two Reynolds numbers.

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Fig. 7

Rms values of the horizontal velocity component for the three tested pipe geometries. Continuous flow at Re = 3500 and Re = 7000 (only for the bifurcated pipe). Color scale in (m/s)2.

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Fig. 8

Turbulent stresses u′v′ for the bifurcated pipe. Continuous flow at two Reynolds numbers. Color scale in (m/s)2.

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Fig. 9

Total shear stress as a function of the radial coordinate at the end of the straight pipe. The continuous line represents the linear solution for pipe flows.

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Fig. 10

Viscous shear stresses for the three tested pipes. Continuous flow at Re = 3500 and Re = 7000 (only for the bifurcated pipe). Color scale in N/m2.

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Fig. 11

Pulsating flow in the straight pipe: overlapping of profiles at different phases (at the top). Comparison with profiles reported by Oertel [18] (at the bottom).

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Fig. 12

Pulsating flow in the straight pipe: at the top, flow reversal at phase number 2 (t/T ≈ 0), at the bottom at phase number 23 (t/T ≈ 0.4) as indicated at the top of the figure

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Fig. 13

Turbulent stresses u′v′ (on the left) and viscous stresses (on the right) for the straight pipe in the pulsating flow at three different phases (indicated at the top of each figure). Color scale in (m/s)2 (turbulent stresses) and N/m2 (viscous stresses).

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Fig. 14

Pulsating flow in the reduced section pipe: phases 2 and 24 as indicated at the top of each figure

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Fig. 15

Turbulent stresses u′v′ (on the left) and viscous stresses (on the right) for the reduced section pipe in the pulsating flow at three different phases (indicated at the top of each figure). Color scale in (m/s)2 (turbulent stresses) and N/m2 (viscous stresses).

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Fig. 16

Pulsating flow in the bifurcated pipe at phases indicated at the top of each figure

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Fig. 17

Turbulent stresses u′v′ (on the left) and viscous stresses (on the right) for the bifurcated pipe in the pulsating flow at three different phases (indicated at the top of each figure). Color scale in (m/s)2 (turbulent stresses) and N/m2 (viscous stresses).

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