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Research Papers: Fundamental Issues and Canonical Flows

The Topology of a Precessing Flow Within a Suddenly Expanding Axisymmetric Chamber

[+] Author and Article Information
Xiao Chen, Zhao F. Tian, Richard M. Kelso

Centre for Energy Technology (CET)
School of Mechanical Engineering,
The University of Adelaide,
Adelaide 5005, Australia

Graham J. Nathan

Centre for Energy Technology (CET)
School of Mechanical Engineering,
The University of Adelaide,
Adelaide 5005, Australia
e-mail: graham.nathan@adelaide.edu.au

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received November 8, 2016; final manuscript received January 31, 2017; published online April 20, 2017. Assoc. Editor: Kwang-Yong Kim.

J. Fluids Eng 139(7), 071201 (Apr 20, 2017) (10 pages) Paper No: FE-16-1732; doi: 10.1115/1.4035950 History: Received November 08, 2016; Revised January 31, 2017

A comprehensive study on the flow structure of an ensemble-averaged fluidic precessing jet (FPJ) flow is reported. This study is based on the concepts of critical point theory, previous experimental data, and validated simulation results. The unsteady k–ω shear stress transport (SST) turbulence model was adopted for the simulation, which provided high resolution flow details. The numerical model successfully reproduced the four main flow features of the FPJ flow. The predicted equivalent diameter and the centerline velocity of the phase-averaged FPJ flow were compared against the measured results and achieved reasonable agreement. The streamlines, velocity, and vorticity contours in a series of cross-sectional planes are presented. The calculated streamlines at the surfaces of the nozzle and the center-body (CB) are compared with previously deduced surface flow patterns. With these methods, a vortex skeleton with six main vortex cores of the FPJ flow within the nozzle is identified for the first time. This skeleton, which is illustrated diagramatically, is deduced to be responsible for the jet precession.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

The geometry and dimensions of the FPJ nozzle with a smoothly contraction inlet and a CB

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Fig. 2

Mesh of the current model: (a) the whole domain, (b) detailed view of the FPJ nozzle, (c) the longitudinal plane through the nozzle, and (d) the cross-sectional plane through the nozzle

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Fig. 3

Qualitative comparison of the FPJ flow pattern and the main flow features that are (a) obtained from the CFD simulation and (b) derived based on the measured phase-averaged axial and radial velocity [9]

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Fig. 4

Measured [9] and predicted centerline velocity (ujet,cl) decay of the phase-averaged jet. Here, the bulk nozzle inlet velocity (uo) is 78.7 m/s.

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Fig. 5

Measured [9] and predicted normalized equivalent diameters (Deq) of the phase-averaged precessing jet. Refer to Fig. 1 for symbols and coordinates.

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Fig. 6

Measured [30] and calculated total fluctuation energy (Ef) profile at x/d = 14.45. The total fluctuation energy is normalized with uo2 and the abscissa is normalized with the diameter of the nozzle's exit De.

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Fig. 7

The calculated streamlines and normalized axial velocity contours within the internal cross-sectional planes within the FPJ nozzle

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Fig. 8

A comparison of the calculated and experimental derived flow pattern on the surfaces of the CB: (a) the calculated streamlines on the upstream and (b) downstream face of the CB. Also shown is (c) the surface flow pattern on the downstream face of the CB that is deduced based on visualization study of a steady deflected jet from the FPJ nozzle [3].

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Fig. 9

Cross-sectional view of (a) the streamlines and critical points derived from the present calculations, (b) the predicted streamlines at the same phase, and (c) the calculated normalized axial velocity field (color figure available online)

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Fig. 10

A comparison of the calculated and experimentally derived flow patterns over the internal surface for configurations of the FPJ and the OTJ nozzles: (a) ensemble-averaged flow pattern that is calculated from the present FPJ nozzle, (b) derived from the present calculation, (c) mean flow pattern obtained in the experiment [1], and (d) ensemble-averaged flow pattern derived from the experimental results for a closely related OTJ nozzle [13]. Note that the dotted lines indicate the location of the CB.

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Fig. 11

The position of vortex core A within the FPJ flow shown with the related calculated vorticity contours in cross-sectional planes. The unit of the vorticity is s−1.

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Fig. 12

Calculated contour of normalized axial velocity, vorticity, and relative pressure on four cross-sectional planes x/D = 0.775, 1.075, 1.375, and 1.675. The dotted lines show the half-width of the jet based on the axial velocity, following Wong et al. [9]. Note that the reference pressure being the atmospheric pressure outside the chamber.

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Fig. 13

The position of vortex core B within the FPJ flow shown with (a) the calculated vorticity contours and (b) the predicted sectional streamlines within the FPJ nozzle. The unit of the vorticity is s−1.

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Fig. 14

(a) The position of vortex core C within the FPJ flow shown with the related calculated vorticity contours and (b) the calculated vorticity contour at the nozzle surface. The unit of the vorticity is s−1.

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Fig. 15

The position of vortex core D within the FPJ flow shown with the calculated vorticity contours in cross-sectional planes. The unit of the vorticity is s−1.

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Fig. 16

The calculated vorticity contours in three cross-sectional planes at (a) x/D = 2.455, (b) x/D = 0.575, (c) x/D = 2.725, and (d) the position of vortex core E within the FPJ flow. The unit of the vorticity is s−1.

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Fig. 17

The position of vortex core F within the FPJ flow shown with the calculated vorticity contours in cross-sectional planes. The unit of the vorticity is s−1.

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Fig. 18

The proposed vortex skeleton of the ensemble-averaged FPJ flow. The black arrow above the nozzle chamber indicates the precession direction.

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