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Research Papers: Multiphase Flows

Influence of Inertial Particles on Turbulence Characteristics in Outer and Near Wall Flow as Revealed With High Resolution Particle Image Velocimetry

[+] Author and Article Information
Ammar Saber

Fluid and Experimental Mechanics Division,
Luleå University of Technology,
Luleå 971 87, Sweden;
Mechanical Engineering Department,
University of Mosul,
Mosul 41001, Iraq
e-mail: ammhaz@ltu.se

T. Staffan Lundström

Fluid and Experimental Mechanics Division,
Luleå University of Technology,
Luleå 971 87, Sweden
e-mail: staffan.lundstrom@ltu.se

J. Gunnar I. Hellström

Fluid and Experimental Mechanics Division,
Luleå University of Technology,
Luleå 971 87, Sweden
e-mail: gunnar.hellstrom@ltu.se

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received June 25, 2015; final manuscript received March 24, 2016; published online June 6, 2016. Assoc. Editor: Mark R. Duignan.

J. Fluids Eng 138(9), 091303 (Jun 06, 2016) (12 pages) Paper No: FE-15-1428; doi: 10.1115/1.4033369 History: Received June 25, 2015; Revised March 24, 2016

A fully developed turbulent particle-gas flow in a rectangular horizontal channel 100 × 10 × 4000 mm3 is disclosed with high spatial resolution two-dimensional (2D) particle image velocimetry (PIV). The objective is to increase the knowledge of the mechanisms behind alterations in turbulent characteristics when adding two sets of relatively large solid spherical particles with mean diameters of 525 and 755 μm and particle size distributions of 450–600 and 710–800 μm, respectively. Reynolds numbers are 4000 and 5600 and relatively high volume fraction of 5.4 × 10−4 and 8.0 × 10−4 are tested. Both the near wall turbulent boundary layer flow and outer core flow are considered. Results show that the carrier phase turbulent intensities increase with the volume fraction of the inertial particles. The overall mean flow velocity is affected when adding the particles but only to a minor extent. Near the wall, averaged velocity decreases while fluctuating velocity components increase when particles are added to the flow. Quadrant analysis shows the importance of sweep near the wall and ejection events in the region defined by y+ > 20. In conclusion, high inertia particles can enhance turbulence even at relatively low particle Reynolds number <90. In the near bottom wall region, particles tend to be a source of instability reflected as enhancement in rms values of the normal velocity component.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Schematic diagram of the experimental setup

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Fig. 2

Streamwise gradients in pixels within interrogation area perpendicular to the flow stream

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Fig. 3

Absolute uncertainty normalized by friction velocity

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Fig. 4

Wall location detection close-up images. The seeding particles are marked with red circles and respective mirror-reflection is marked with blue circles.

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Fig. 5

Mean velocity field in the vicinity of line c-c, white rectangular represent the near wall region

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Fig. 6

Mean velocity profiles (a) unladen velocity profile for different Reynolds number, (b) velocity profile at Re = 4000 for different volume fractions and particle sizes, and (c) velocity profile at Re = 5600 for different volume fractions and particle sizes

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Fig. 7

Mean particle velocity normalized with unladen gas velocity at the center for: (a) Re = 5600 and dp = 525 μm, (b) Re = 4000 and dp = 525 μm, (c) Re = 5600 and dp = 725 μm, and (d) Re = 4000 and dp = 725 μm, continued

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Fig. 8

Fluctuating velocity profiles in the x-direction (urms/Ucl) for different laden cases compared with unladen case

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Fig. 9

Fluctuating velocity profiles in the y-direction vrms/Ucl for different leaden cases compared with unleaded case

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Fig. 10

Particle light intensity accumulation case 10 (Note: The laser-light that illuminates the glass particles is from the top side.)

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Fig. 11

Streamwise turbulence intensity at the center line as a function of particles; (a) volume fraction and (b) length scale ratio (particle diameter divided by the energetic length scale)

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Fig. 12

Mean velocity normalized with friction velocity for distance up to y+ = 50 different cases; (a) dp = 755 μm and (b) dp = 525 μm

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Fig. 13

Streamwise fluctuating velocity component normalized with friction velocity for distance up to y+ = 50; (a) dp = 755 μm and (b) dp = 525 μm

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Fig. 14

Normal fluctuating velocity component normalized with friction velocity for distance up to y+ = 50; (a) dp = 755 μm and (b) dp = 525 μm

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Fig. 15

Reynolds stress distribution for case 6

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Fig. 16

Contribution to Reynolds shear stress from (a) Q2 and (b) Q4

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