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Design Innovation

Flow-Excited Acoustic Resonance in Industry

[+] Author and Article Information
Samir Ziada1

Laboratory of Fluid Mechanics and Acoustics, Ecole Centrale de Lyon, 69134 Ecully Cedex, Franceziadas@mcmaster.ca

1

Permanent address: McMaster University, Hamilton, Ontario, Canada.

J. Pressure Vessel Technol 132(1), 015001 (Jan 05, 2010) (9 pages) doi:10.1115/1.4000379 History: Received April 28, 2009; Revised September 17, 2009; Published January 05, 2010; Online January 05, 2010

The excitation mechanism of acoustic resonances has long been recognized, but the industry continues to be plagued by its undesirable consequences; manifested in severe vibration and noise problems in a wide range of industrial applications. This paper focuses on the nature of the acoustic resonance excitation mechanism for the case of closed side branches because of its relative importance to industrial applications. Design charts are presented for the Strouhal number at the onset of acoustic resonance and for the acoustic source strength representing the integral effect of the shear layer at the mouth of the side branch. Because these design charts are developed from tests of cylindrical pipes conveying turbulent flow at high Reynolds numbers, they can be used in industrial applications to predict the onset flow velocity and the intensity of acoustic resonances in side branches. Two industrial examples involving flow-excited acoustic resonance of closed side branches are presented. The first example deals with acoustic fatigue failure of the steam dryer in a boiling water reactor due to acoustic resonance in the main steam piping system, whereas the second example considers acoustic resonances in the roll posts of the short take-off vertical lift (STOVL) joint strike fighter. In both examples, effective means to alleviate the acoustic resonance mechanism are discussed.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic presentation of flow-excited acoustic resonance mechanism

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Figure 2

Flow visualization and acoustic particle velocity at two different time instants during the acoustic resonance cycle of a deep cavity

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Figure 3

Various arrangements of closed side branches and associated acoustic pressure distributions of the first acoustic mode. The arrows in the bottom figures indicate the acoustic flux of the resonant acoustic modes (13).

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Figure 4

Acoustic response of coaxial side branches showing the effect of the branch length L (i.e., the effect of acoustic attenuation): △, L=61 cm, test pressure Ps=3.5 bar; ○, L=110 cm, Ps=4 bar; ▲, L=158.5 cm, Ps=4 bar(13)

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Figure 5

Design chart of critical Strouhal number (So=fd/Vo) at the onset of resonance (13)

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Figure 6

Model of the aeroacoustic source resulting from the interaction of the shear layer oscillation with the resonant sound field

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Figure 7

Experimentally determined source term Q presented in the Q-complex plane. The acoustic particle velocity (u/V) and the Strouhal number (S) are taken as parameters (14).

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Figure 8

Oscillation amplitude as function of flow velocity for different depth modes for coaxial branches. The resonance frequency is 137 Hz in all four cases. The symbols indicate measured data and the lines are computed from the experimentally determined source term (14).

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Figure 9

Schematic of the upper section of a BWR showing the steam separator, steam dryer, inlet nozzle to a MSL, and the path of steam flow through the dryer and into the MSL (20)

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Figure 10

Steam dryer assembly of quad cities unit 2 (top left) and details of the acoustic fatigue failure on the outer hood (23)

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Figure 11

Power spectral density of fluctuating pressure on the dryer showing the tonal excitation near 150 Hz (24)

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Figure 12

Locations of the safety relief valves on the main steam lines (25)

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Figure 13

Geometry of the standpipe of safety relief valves. Left: original design; middle: alternative design but impractical in the present case; right: final solution with acoustic side branch (26).

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Figure 14

Rolls-Royce vertical lift system® showing the engine and roll posts configuration of the joint strike fighter (www.rolls-royce.com/defence_aerospace/products/combat/liftsystem/default.jsp)

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Figure 15

Geometry of the test section showing the inner cylinder, splitter plates, and microphone locations m1 and m2. The splitter plates were not used in the original design, but were added later as a countermeasure (27).

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Figure 16

Frequency spectrum and mode shape for the first acoustic mode f1(27)

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Figure 17

Overview of the system acoustic response. Top figure shows acoustic resonance (lock-in) frequency with the straight lines representing the Strouhal numbers S=0.55 and 0.27. The bottom figure shows dimensionless acoustic pressure as functions of flow velocity (27).

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Figure 18

SPL in dB measured at the branch closed end (27)

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Figure 19

Pressure spectra at the end of (a) the shortened and (b) the unchanged branches for V=30 m/s, ΔL/L1=42%. (c) Acoustic pressure (◻) at f1′ in the unchanged branch and (×) at f1″ in the shortened branch for ΔL/L1=42%(27).

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Figure 20

Acoustic pressure of the duct with and without splitter plates (27)

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