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Research Papers: Flows in Complex Systems

An Inquiry of the Friction Factor “Jump” Phenomenon in Hole-Pattern Seals

[+] Author and Article Information
Aarthi Sekaran

Turbomachinery Laboratory,
Texas A&M University,
College Station, TX 77843
e-mail: aarthi.sekaran11@gmail.com

Gerald Morrison

Mem. ASME
Turbomachinery Laboratory,
Texas A&M University,
College Station, TX 77843
e-mail: gmorrison@tamu.edu

Devesh Ranjan

Mem. ASME
George W. Woodruff School of Mechanical
Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332
e-mail: devesh.ranjan@me.gatech.edu

1Corresponding author.

2Current address: Engineering Mechanics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received March 18, 2015; final manuscript received February 25, 2016; published online May 2, 2016. Assoc. Editor: Mark F. Tachie.

J. Fluids Eng 138(8), 081102 (May 02, 2016) (11 pages) Paper No: FE-15-1184; doi: 10.1115/1.4033023 History: Received March 18, 2015; Revised February 25, 2016

Experiments measuring the leakage rate through hole-pattern seals operating at high pressures of up to 8400 kPa reveal the presence of an abrupt variation in the friction factor (up to a factor of three) with change in the pressure difference across the seal. The measured pressure fluctuations suggest that this observation may, perhaps, be understood as a change in fluid instability modes across the cavities of the seal. A more detailed investigation via large eddy simulations (LES) suggest that the switching from shear layer instability mode to a wake instability mode, a phenomenon well known in fundamental studies of cavity flow (without a top bounding wall), is responsible for the observed variation.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

(a) Layout and configuration of a honeycomb seals [1] and (b) cutaway view of hole-pattern, honeycomb, and labyrinth seals [2]

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Fig. 2

Flow loop for the flat-plate test rig

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Fig. 3

(a) Detailed view of the flat-plate test rig [6] and (b) closer view of plates showing the locations of pressure probes and thermocouples [9]

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Fig. 4

(a) Variation of m˙ with ΔP showing the abrupt change in flow rate along with chosen flow parameters for computational fluid dynamics (CFD) simulations and (b) variation of ff with ΔP showing the friction factor jump

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Fig. 5

Pressure distribution along the length of the 2D plate as a function of pressure drop

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Fig. 6

Mach number distribution along the length of the 2D plate as a function of pressure drop

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Fig. 7

Friction factor distribution along the length of the 2D plate as a function of pressure drop

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Fig. 8

Normalized FFT of pressure spectra taken at different pressure drops

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Fig. 15

(a) Vorticity contours superposed with streamlines showing the formation and transport of generated vortices at condition 1 and (b) vorticity contours superposed with streamlines showing the formation and transport of generated vortices at condition 2

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Fig. 14

(a) Z vorticity contours at upstream cavity edge showing the formation of crest for ΔP = 1381 kPa at 5 × 10−6 s, (b) pressure contours at upstream cavity edge showing the formation of crest for ΔP = 1381 kPa at 5 × 10−6 s, (c) Z vorticity contours at upstream cavity edge showing the detachment of the vortex for ΔP = 1381 kPa at 9 × 10−6 s, and (d) pressure contours at upstream cavity edge showing the detachment of the vortex for ΔP = 1381 kPa at 9 × 10−6 s

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Fig. 13

Variation of Z vorticity with time at condition 2 (ΔP = 1381 kPa)

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Fig. 12

(a) Close-up of Z vorticity contours at upstream cavity edge showing the onset of instability (ΔP = 1680 kPa), (b) close-up of Z vorticity contours at upstream cavity edge showing the roll-up of the shear layer (ΔP = 1680 kPa), and (c) close-up of upstream cavity edge showing the pressure contours at the roll-up of shear layer (ΔP = 1680 kPa)

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Fig. 11

Variation of Z vorticity with time at condition 1 (ΔP = 1680 kPa)

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Fig. 10

Pressure monitored over time to study grid independence and determine statistical stability

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Fig. 9

Representative mesh of simulation domain

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Fig. 16

(a) FFT of pressure distribution at the downstream lip of the cavity for the case with ΔP = 1680 kPa and (b) FFT of pressure distribution at the downstream lip of the cavity for the case with ΔP = 1381 kPa

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