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

A Numerical Study on the Turbulent Schmidt Numbers in a Jet in Crossflow

[+] Author and Article Information
Elizaveta M. Ivanova

Research Scientist
e-mail: elizaveta.ivanova@dlr.de

Berthold E. Noll

Head of Computer Simulation
e-mail: berthold.noll@dlr.de

Manfred Aigner

Professor Director of Institute
e-mail: manfred.aigner@dlr.de
Institute of Combustion Technology,
German Aerospace Center (DLR),
Stuttgart, 70569Germany

This statement is not meant to imply that the results of LES are independent of the SGS scalar transport model, but a thorough study on this subject is not the focus of the present work.

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 14, 2012; final manuscript received August 1, 2012; published online November 30, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(1), 011505 (Nov 30, 2012) (10 pages) Paper No: GTP-12-1277; doi: 10.1115/1.4007374 History: Received July 14, 2012; Revised August 01, 2012

This work presents a numerical study on the turbulent Schmidt numbers in jets in crossflow. This study contains two main parts. In the first part, the problem of the proper choice of the turbulent Schmidt number in the Reynolds-averaged Navier-Stokes (RANS) jet in crossflow mixing simulations is outlined. The results of RANS employing the shear-stress transport (SST) model of Menter and its curvature correction modification and different turbulent Schmidt number values are validated against experimental data. The dependence of the optimal value of the turbulent Schmidt number on the dynamic RANS model is studied. Furthermore, a comparison is made with the large-eddy simulation (LES) results obtained using the wall-adapted local eddy viscosity (WALE) model. The accuracy given by LES is superior in comparison to RANS results. This leads to the second part of the current study, in which the time-averaged mean and fluctuating velocity and scalar fields from LES are used for the evaluation of the turbulent viscosities, turbulent scalar diffusivities, and the turbulent Schmidt numbers in a jet in crossflow configuration. The values obtained from the LES data are compared with those given by the RANS modeling. The deviations are discussed, and the possible ways for the RANS model improvements are outlined.

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References

Figures

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Fig. 1

Flow configuration, computational domain, and coordinate system

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Fig. 2

Computational grid for LES calculations. (a) x/d = 0 and x/d = 15 planes. (b) z/d = 0 plane.

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Fig. 3

Components of the mean velocity vector U¯x and U¯y. z/d = 0. LES and two RANS turbulence models in comparison with experimental data.

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Fig. 4

Turbulent kinetic energy k and Reynolds shear stress u'xu'y¯. z/d = 0. LES and two RANS turbulence models in comparison with experimental data.

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Fig. 5

RMS of the x- and y-velocity fluctuations. z/d = 0. LES and two RANS turbulence models in comparison with experimental data.

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Fig. 6

Mean transported passive scalar, different y/d planes. LES and two RANS turbulence models (σt = 1.0) in comparison with experimental data. (a) Experimental data, y/d = 7. (b) WALE LES, y/d = 7. (c) SST, y/d = 7. (d) SST curv. corr., y/d = 7. (e) Experimental data, y/d = 5. (f) WALE LES, y/d = 5. (g) SST, y/d = 5. (h) SST curv. corr., y/d = 5.

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Fig. 7

Transported passive scalar. LES and two RANS turbulence models at σt = 1.0 in comparison with experimental data.

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Fig. 8

Turbulent scalar flux in x-direction. z/d = 0. LES and two RANS turbulence models at σt = 1.0 in comparison with experimental data.

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Fig. 9

Transported passive scalar. z/d = 0. Different turbulent Schmidt numbers σt.

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Fig. 10

Dimensionless turbulent viscosity νt/ν evaluated from LES data in two different ways. y/d = 7, z/d = 0. The raw and the smoothed curves.

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Fig. 11

Dimensionless turbulent viscosity νt/ν evaluated from LES data and resulting from RANS modeling. y/d = 7, z/d = 0.

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Fig. 12

Dimensionless turbulent scalar diffusivity αt/α evaluated from LES data in different ways. y/d = 7, z/d = 0.

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Fig. 13

Dimensionless turbulent scalar diffusivity αt/α evaluated from LES data and resulting from RANS modeling at different σt

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Fig. 14

Turbulent Schmidt number σt evaluated from LES data

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