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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Large-Eddy Simulation of Turbulent Mixing of a Jet in Cross-Flow

[+] Author and Article Information
Mostafa Esmaeili

School of Mechanical Engineering,
College of Engineering,
University of Tehran,
Tehran 1439957131, Iran
e-mail: mosesmaeili@ut.ac.ir

Asghar Afshari

School of Mechanical Engineering,
College of Engineering,
University of Tehran,
Tehran 1439957131, Iran
e-mail: afsharia@ut.ac.ir

Farhad A. Jaberi

Department of Mechanical Engineering,
Michigan State University,
East Lansing, MI 48824
e-mail: jaberi@egr.msu.edu

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received November 12, 2014; final manuscript received February 14, 2015; published online March 24, 2015. Assoc. Editor: Song-Charng Kong.

J. Eng. Gas Turbines Power 137(9), 091510 (Sep 01, 2015) (16 pages) Paper No: GTP-14-1618; doi: 10.1115/1.4029915 History: Received November 12, 2014; Revised February 14, 2015; Online March 24, 2015

An Eulerian–Lagrangian mathematical/computational methodology is employed for large-eddy simulation (LES) and detailed study of turbulent mixing in jet in cross-flow (JICF) configuration. Accurate prediction of mixing in JICF is crucially important to the development of advanced combustion systems. A high-order multiblock finite difference (FD) computational algorithm is used to solve the Eulerian velocity and pressure equations in a generalized coordinate system. The composition field, describing the mixing, is obtained from the filtered mass density function (FMDF) and its stochastic Lagrangian Monte-Carlo (MC) solver. Our simulations are shown to accurately predict the important flow features present in JICF such as the counter-rotating vortex pair (CVP), horseshoe, shear layer, and wake vortices. The consistency of the FD and MC parts of the hybrid LES/FMDF model is established for the simulated JICF in various conditions, indicating the numerical accuracy of the model. The effects of parameters influencing the jet penetration, entrainment, and turbulent mixing such as the jet velocity profile, and jet pulsation are investigated. The results show that the jet exit velocity profile significantly changes the trajectory and mixing of injected fluid. The jet pulsation is also shown to enhance the mixing depending on the flow Strouhal number. The LES/FMDF results are shown to be in good agreement with the available experimental data, confirming the reliability of LES/FMDF method for numerical simulation of turbulent mixing in complex flow configurations.

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References

Figures

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Fig. 1

Sketch of the computational domain

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Fig. 2

The computed ratio of Δ/η in the center-plane based on Eqs. (14) and (15)

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Fig. 3

Number of cells for different values of υeff/υ

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Fig. 4

3D isosurface of the instantaneous scalar concentration (φ˜=0.05) and MC particles

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Fig. 5

Contours of the instantaneous and time-averaged values of the filtered scalar concentration in the center-plane obtained by LES/FMDF, (a) instantaneous FD values, (b) instantaneous MC values, (c) time-averaged FD values, and (d) time-averaged MC values

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Fig. 6

Profiles of mean and instantaneous scalar concentration predicted by FD and MC solvers at x/D = 3.67. 〈〉 denotes the time-averaged quantity.

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Fig. 7

Comparison between LES with different SGS models and experiment data [17] at x/D = 3.67. (a) Mean velocity magnitude and (b) normalized RMS fluctuations of the velocity magnitude.

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Fig. 8

Comparison between our numerical results and published experimental [58] and numerical data [15,59] obtained for the jet trajectory in the center-plane

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Fig. 9

Vertical profiles of mean velocity magnitude at four streamwise positions in the center-plane. Solid lines indicate present LES and circles indicate the experimental data [17].

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Fig. 10

Vertical profiles of normalized RMS fluctuations of the velocity magnitude at different streamwise positions in the center-plane. Solid lines indicate present LES and circles indicate the experimental data [17].

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Fig. 11

Profiles of mean passive-scalar concentration obtained from FMDF calculations at four streamwise positions in the center-plane. Solid lines indicate present LES and circles indicate the experimental data [17].

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Fig. 12

Profiles of RMS fluctuations of the passives scalar concentration obtained from FMDF calculations at different streamwise positions in the center-plane. Solid lines indicate present LES and circles indicate the experimental data [17].

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Fig. 13

Three-dimensional streamlines computed from the mean flow-field in two views (displayed as volume rod colored by the mean streamwise velocity)

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Fig. 14

The isosurface of the Q-criterion, applied to (a) mean flow-field and (b) instantaneous flow-field

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Fig. 15

Average streamlines in center-plane (z = 0). Symbols, jet trajectory; N, node; and F, focal point.

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Fig. 16

Average streamlines in z = 0.5D plane; S, saddle; and F, focal point

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Fig. 17

Average streamlines in (a) x = 2D and (b) x = 5D; S, saddle; and F, focal point

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Fig. 18

Visualization of dimensionless mean-flow data in the center-plane. (a) Streamwise velocity and (b) vertical velocity.

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Fig. 19

Effect of the jet velocity profile on the jet trajectory

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Fig. 20

Jet volume flux along the jet trajectory curve length for two velocity profiles; compared with the result of Yuan et al. [14] and the Ricou–Spalding correlation for an axisymmetric jet [63]

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Fig. 21

Effect of the jet velocity profile on the (a) mixedness and (b) spatial unmixedness

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Fig. 22

The averaged scalar field in the center-plane (z = 0): (a) pulsating jet at St = 0.15 and (b) nonpulsating jet

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Fig. 23

The instantaneous scalar field in the center-plane (z = 0) for pulsating jet in St = 0.15 at different Tf. (a) Tf = 0.25; (b) Tf = 0.5; (c) Tf = 0.75; and (d) Tf = 1.

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Fig. 24

Penetration depth variations with Strouhal number at different streamwise positions

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Fig. 25

Jet spreading in spanwise and vertical directions for nonpulsating and sine wave pulsating jets

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Fig. 26

Entrainment ratio for nonpulsating and sine wave pulsating jets

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Fig. 27

Mixing criteria, (a) spatial unmixedness variations with Strouhal number (b) mixing enhancement calculated from the increment rate of mixedness parameter

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