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Research Papers: Gas Turbines: Turbomachinery

Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Wake Dynamics Validation

[+] Author and Article Information
Ryan Blanchard

Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: rpberlin@vt.edu

Wing Ng

Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: wng@vt.edu

Todd K. Lowe

Virginia Polytechnic Institute and State University,
103-C Randolph Hall,
Blacksburg, VA 24061
e-mail: kelowe@vt.edu

Uri Vandsburger

Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: uri@vt.edu

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 24, 2014; final manuscript received March 25, 2014; published online July 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(12), 122603 (Jul 02, 2014) (12 pages) Paper No: GTP-14-1119; doi: 10.1115/1.4027556 History: Received February 24, 2014; Revised March 25, 2014

In this article, we describe a novel use of proper orthogonal decomposition (POD) for validation of the structure of dominant flow features in the wake of a bluff-body flameholder. Large-eddy simulations (LES) using both FLUENT and OpenFOAM were conducted based on experiments with planar particle-image velocimetry (PIV) measurements of the same geometry and conditions. With the vision of extending the LES to reacting flows, a validation process is presented that involves a comparison of experimental and computational results, beginning with single-point mean statistics and then extended to the dynamic modes of the data sets as obtained using POD of the instantaneous flow field results. The results exhibit quantitative agreement between both shapes and mode magnitudes for the first POD modes of the measured and simulated data.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Large eddy simulation of nonreacting flow around a bluff body from the current work showing isosurfaces of the Q-criterion. The alternating shedding pattern in the bluff body's wake can be seen.

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Fig. 4

Transparent view of CAD model of the test section showing the locations of the three windows relative to the vee-gutter flameholder and the PIV laser sheet

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Fig. 7

Illustration of relative sizes and locations of sampling planes relative to the flameholder: 100 × 100 CFD sample grid points (blue) compared to the effective viewing area for the PIV measurements

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Fig. 8

Mean streamwise velocity plots as measured by Pitot probe and as simulated by FLUENT LES

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Fig. 2

Test section temperature and Mach number limitations from facility constraints

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Fig. 3

Schematic of experiment showing the three sections of the rig and the locations of the fuel injection, vee-gutter flameholder, and windows

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Fig. 5

Isometric view of dimensions of the domain used in the LES models based on the width of the flameholder w = 3.05 cm

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Fig. 6

Plan view dimensions of the domain used in LES models, based on the dimension of the vee-gutter flameholder w = 3.05 cm, which has an included angle of 70 deg

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Fig. 9

v2 Reynolds stress spectra spectrum from LES model. Note the peak due to vortex shedding at Str = 0.24 and also the decay rate that seems to correspond to the –5/3 power law rule.

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Fig. 10

Contours of the sum of the first three POD modes (left: v’, right: u’) obtained using results from PIV (top), FLUENT (middle), and OpenFOAM (bottom). The profiles shown in Fig. 11 are taken along the lines show on each plot.

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Fig. 11

Comparison between numerical and experimental values of the first three POD modes. Left: v’, right: u’.

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Fig. 15

Comparison between the baseline domain (left) and the domain with the extended domain (right) with increased distance between the inlet and the vee-gutter to produce a bigger/thicker boundary layer in the vicinity of the vee-gutter

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Fig. 16

Comparison between the sum of the first three POD modes of the baseline simulation (top) and thicker boundary layer configuration (bottom). Contours of the U-component (streamwise) of velocity are shown on the left and V-component contours are shown on the right.

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Fig. 17

Comparison of the v-components (vertical) of velocity of the sum of the first three modes of the baseline simulation and the configuration with the thicker boundary layer

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Fig. 18

Comparison between the sum of the first three POD modes of the baseline simulation (top) and periodic side “wall” configuration (bottom). Contours of the U-component (streamwise) of velocity are shown on the left and V-component contours are shown on the right.

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Fig. 19

Comparison of the first v-components (vertical) of velocity of the sum of the first three modes between baseline simulation and the configuration with periodic sides

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Fig. 20

Comparison between the sum of the first three POD modes of the baseline simulation (top) and turbulent inlet configuration (bottom). Contours of the U-component (streamwise) of velocity are shown on the left and V-component contours are shown on the right.

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Fig. 21

Comparison of the v-components (vertical) of velocity of the sum of the first three modes of the baseline simulation and the configuration with the turbulent inlet

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Fig. 12

Contours of u-velocity component of the sum of the first three POD modes of PIV (top), FLUENT (middle), and OpenFOAM (bottom). The profiles shown in Fig. 13 are taken along the lines shown imposed on each figure.

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Fig. 13

Plot of u-velocity component of the sum of the first three POD modes taken along the lines indicated in Fig. 12

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Fig. 14

Plot of v-velocity component of the sum of the first three POD as isolated at y/w = 0 at the midplane, near the wall and near the wall but with EPOD to recover the near-wall modeshapes using the eigenvectors of the midplane analysis

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Fig. 22

Velocity contours of first three modes of baseline (top) and refined grid (bottom) simulations, showing contours of u’ (left) and v’ (right)

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Fig. 23

Comparison of the v-components (vertical) of velocity of the sum of the first three modes of the baseline simulation and the refined grid simulation

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Fig. 24

Pope criterion contours at midplane for baseline (top) and refined mesh (bottom) cases

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Fig. 25

Computation time versus number of snapshots N showing that the computational time grows proportional to N3 as expected (solid line is ~N3)

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Fig. 26

Second-order convergence rate of the first five eigenvalues

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Fig. 27

Convergence of first three POD modes with increasing number of samples showing a first-order convergence rate

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