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Research Papers: Multiphase Flows

Computations of Particle-Laden Turbulent Jet Flows Based on Eulerian Model

[+] Author and Article Information
Pandaba Patro

e-mail: ppatro@mech.iitkgp.ernet.in

Sukanta K. Dash

e-mail: sdash@mech.iitkgp.ernet.inDepartment of Mechanical Engineering,
IIT,
Kharagpur 721302, India

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received January 6, 2013; final manuscript received August 17, 2013; published online October 3, 2013. Assoc. Editor: Francine Battaglia.

J. Fluids Eng 136(1), 011301 (Oct 03, 2013) (16 pages) Paper No: FE-13-1007; doi: 10.1115/1.4025364 History: Received January 06, 2013; Revised August 17, 2013

Numerical simulations using an Eulerian two-fluid model were performed for spatially developing, two-dimensional, axisymmetric jets issued from a 30-mm-diameter circular nozzle. The nozzle was simulated separately for various flow conditions to get fully developed velocity profiles at its exit. The effect of interparticle collisions in the nozzle gives rise to solids pressure and viscosity, which are modeled using kinetic theory of granular flows (KTGF). The particle sizes are in the range of 30 μm to 2 mm, and the particle loading is varied from 1 to 5. The fully developed velocity profiles are expressed by power law, U=Uc(1-(r/R))N. The exponent, N, is found to be 0.14 for gas phase, irrespective of particle sizes and particulate loadings. However, the solid-phase velocity varies significantly with the particle diameter. For particle sizes up to 200 μm, the exponent is 0.12. The center line velocity (Uc) of the solid phase decreases and, hence, the slip velocity increases as the particle size increases. For 1 mm and 2 mm size particles, the exponent is found to be 0.08 and 0.05, respectively. The developed velocity profiles of both the phases are used as the inlet velocities for the jet simulation. The modulations on the flow structures and turbulent characteristics of gas flow due to the solid particles with different particle sizes and loadings are investigated. The jet spreading and the decay of the centerline mean velocity are computed for all particle sizes and loadings considered under the present study. Additions of solid particles to the gas flow significantly modulate the gas turbulence in the nozzle as well as the jet flows. Fine particles suppress the turbulence, whereas coarse particles enhance it.

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References

Figures

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Fig. 2

Effect of boundary conditions on the axial and radial velocity profiles of both the phases: the velocities are normalized by the centerline velocity

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Fig. 3

Effect of grid on the predictions of (a) gas-phase velocity, (b) solid-phase velocity, and (c) gas turbulent kinetic energy

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Fig. 1

Flow field around a jet, a schematic diagram

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Fig. 4

Computational domain used for the two-phase jet

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Fig. 16

Normalized axial velocity as a function of radial distance: a comparison with the experiments of Abramovich [12] for Reg = 2.2×104

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Fig. 5

Axial development of the normalized centerline velocity for different mesh sizes

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Fig. 6

Normalized mean velocity profiles at X/D = 10 for different mesh sizes

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Fig. 9

Nozzle exit gas-phase velocity profiles for different cases. Symbols are the power function fitting profiles with N = 0.14.

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Fig. 10

Nozzle exit solid-phase velocity profiles for different cases. Symbols are the power function fitting profiles with N = 0.12.

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Fig. 11

Centerline velocity as a function of mean velocity for both phases

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Fig. 12

Nozzle exit solid-phase velocity profiles for (a) dp = 1 mm, N = 0.08 and (b) dp = 2 mm, N = 0.05. Solid-phase density = 2990 kg/m3.

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Fig. 13

Variation of the centerline velocity with mean velocity for the solid phase at (a) dp = 1 mm and (b) dp = 2 mm

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Fig. 14

Radial variation of the gas-phase turbulence intensity. Symbols: turbulence intensity from single-phase flow simulations. Squares ◻ are for case 2, diamonds ◇ are for case 4, and triangles ▽ are for cases 1 and 3.

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Fig. 15

Radial variation of the turbulence intensity with particle diameter

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Fig. 7

Computed (a) gas-phase velocity, (b) solid-phase velocity, and (c) gas turbulent intensity: a comparison with the experiments of Modarress et al. [14] for glass beads at D = 20 mm, β = 0.85, and Reg = 1.33×104 in a vertical downward two-phase flow. Model 1 is algebraic granular temperature model, and model 2 is full granular temperature equation.

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Fig. 8

Computed (a) velocity profiles of both phases and (b) gas turbulent intensity: a comparison with the experiments of Tsuji et al. [31] for polystyrene pellets at D = 30 mm, β = 1.3, and Reg = 2.3×104 in a vertical upward flow. Velocities are nondimensionalized with the centerline velocity of the gas phase.

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Fig. 21

Variations of the jet velocity half-width: (a) different particulate loadings, dp = 200 μm, (b) different particle sizes, β = 1

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Fig. 22

Effect of particulate loading (β) on the mean velocity profiles at X/D = 20, dp = 200μm, and Um = 10 m/s

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Fig. 23

Mean velocity profiles (normalized by the centerline velocity) as a function of the radial distance at different axial positions, dp = 200μm

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Fig. 17

(a) Normalized solid-phase axial velocity as a function of radial distance: a comparison with the experimental data of Frishman et al. [21] for Reg = 5×104,dp = 23μm, and β = 0.62 and (b) effect of interparticle collisions with full granular temperature equation on centerline velocity profiles for dp = 200μm, β = 5, and Reg = 2.06×104

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Fig. 18

Decay of the centerline velocity (normalized by the velocity at the inlet) for different particle sizes: (a) gas phase and (b) solid phase ρs = 2500 kg/m3, β = 1

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Fig. 19

Decay of the centerline velocity (normalized by the velocity at the inlet) for different particulate loadings: (a) gas phase and (b) solid phase ρs = 2500 kg/m3, dp = 200μm

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Fig. 20

Slip velocity profiles along the centerline: (a) different particle diameters, β = 1, and (b) different particle loadings, dp = 200μm

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Fig. 24

Mean velocity profiles as a function of the radial distance at different axial positions for different Stokes numbers (St)

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Fig. 25

Decay of mean velocity along the centerline for different Stokes numbers (St)

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Fig. 27

Variations of (a) turbulent kinetic energy (normalized with respect to the nozzle exit) and (b) turbulent modulations along the centerline for different particle sizes, ρs = 2500 kg/m3, β = 1

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Fig. 28

Variations of (a) turbulent kinetic energy (normalized with respect to the nozzle exit) and (b) turbulent modulations on the center line as a function of the axial distance for different particulate loadings, ρs = 2500 kg/m3, dp = 200μm

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Fig. 29

Variations of the turbulent kinetic energy as a function of the radial distance, β = 1, (a) St = 2, (b) St = 100

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Fig. 30

Turbulent modulation as a function of the radial distance, β = 1, (a) St = 2, (b) St = 100

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Fig. 26

Normalized velocities at X/D = 20 for different Stokes number (St)

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