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Research Papers: Fluid-Structure Interaction

Shear Layer Driven Acoustic Modes in a Cylindrical Cavity

[+] Author and Article Information
David B. Stephens

NASA Glenn Research Center,
Cleveland, OH 44070

Francisco R. Verdugo

Dipartimento di Ingegneria
Meccanica e Industriale,
Università degli Studi Roma Tre,
Via della Vasca navale,
Rome 79 - 00146, Italy

Gareth J. Bennett

Assistant Professor
Department of Mechanical and
Manufacturing Engineering,
Trinity College Dublin,
Dublin 2, Ireland
e-mail: gareth.bennett@tcd.ie

1This work was performed while the author was employed as a Visiting Scholar at Trinity College Dublin and is not a work of the U.S. Government.

2Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received September 13, 2013; final manuscript received February 13, 2014; published online August 19, 2014. Assoc. Editor: Samir Ziada.

J. Pressure Vessel Technol 136(5), 051309 (Aug 19, 2014) (8 pages) Paper No: PVT-13-1161; doi: 10.1115/1.4026866 History: Received September 13, 2013; Revised February 13, 2014

This paper describes the interior acoustic pressure of a cylindrical cavity driven by a shear layer. Existing cavity flow literature is generally focused on rectangular cavities, where the resonance is either longitudinal or the result of excited depth modes inside the cavity. The design of the present circular cavity is such that azimuthal duct modes can be excited in various combinations with depth modes depending on free stream velocity. An acoustic simulation of the system was used to identify the modes as a function of frequency when the system is driven by an acoustic point source. With appropriate manipulation of the free stream flow, abrupt mode switching and mode oscillation were both observed, and a condition with a dominant azimuthal mode was found. The strength of the lock-on was documented for the various resonance conditions, and the effects of the cavity opening size and location were studied.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Schematic of cavity experiment showing the single microphone location. Not to scale.

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Fig. 2

Sketch showing variation in cavity opening location. Not to scale.

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Fig. 3

Sketch showing variation in cavity opening lengths. Not to scale.

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Fig. 4

Photograph of experiment looking through the bottom of the cavity toward the cavity opening to the wind tunnel. The PIV camera is visible above and the cavity is instrumented with two rings of microphones.

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Fig. 5

Cavity acoustic transfer function between the unsteady pressure at the cavity opening and the interior of the cavity. Simulation and experiment shown.

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Fig. 6

Examples of linear fit in the calculation of SoL. Pressure amplitudes at 73 Hz (a) and 376 Hz (b) as a function of the wind tunnel flow speed. L = 45 mm, Δ = 0 mm.

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Fig. 12

Strength of lock-on contours of 10 dB showing effect of cavity opening location: Δ = 0

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Fig. 11

Strength of lock-on contours of 10 dB showing effect of cavity opening location: L = 40 mm

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Fig. 8

Pressure spectral density inside the cavity subjected to grazing flow: L = 40 mm, Δ = 100 mm

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Fig. 10

Pressure spectral density inside the cavity subjected to grazing flow: L = 40 mm and Δ = 0 mm

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Fig. 9

Pressure spectral density inside the cavity subjected to grazing flow: L = 40 mm and Δ = 40 mm

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Fig. 7

Internal cavity pressure predicted by WEM code. This example shows a (1,0,0.5) mode, occuring at He = 2.01. The black square denotes source location. (a) Isometric view, (b) slice along streamwise centerline, and (c) cavity top.

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Fig. 13

Internal cavity pressure with U = 48.5 m/s, L = 45 mm, Δ = 0

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Fig. 14

Internal cavity pressure with U = 49.0 m/s, L = 45 mm and Δ = 0

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Fig. 15

Internal cavity pressure spectrum measured at 26 m/s (averaged over time)

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Fig. 16

Spectrogram of cavity pressure at 26 m/s showing mode switching

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