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Research Papers: Fluid-Structure Interaction

Passive Control of Trapped Mode Resonance of Ducted Cavities

[+] Author and Article Information
M. Bolduc, M. Elsayed, S. Ziada

Department of Mechanical Engineering,
McMaster University,
Hamilton, ON L8S4L7, Canada

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received August 25, 2013; final manuscript received April 5, 2014; published online August 19, 2014. Assoc. Editor: Jong Chull Jo.

J. Pressure Vessel Technol 136(5), 051311 (Aug 19, 2014) (6 pages) Paper No: PVT-13-1144; doi: 10.1115/1.4027377 History: Received August 25, 2013; Revised April 05, 2014

Gas flow over ducted cavities can excite strong acoustic resonances within the confined volumes housing the cavities. When the wavelength of the resonant acoustic modes is comparable with, or smaller than, the cavity dimensions, these modes are referred to as trapped acoustic modes. The flow excitation mechanism causing the resonance of these trapped modes in axisymmetric shallow cavities has been investigated experimentally in a series of papers by Aly and Ziada (2010, “Flow-Excited Resonance of Trapped Modes of Ducted Shallow Cavities,” J. Fluids Struct., 26, pp. 92–120; 2011, “Azimuthal Behaviour of Flow-Excited Diametral Modes of Internal Shallow Cavities,” J. Sound Vib., 330, pp. 3666–3683; 2012, “Effect of Mean Flow on the Trapped Modes of Internal Cavities,” J. Fluids Struct., 33, pp. 70–84). In this paper, the same experimental set-up is used to investigate the effect of the upstream edge geometry on the acoustic resonance of trapped modes. The investigated geometries include sharp and rounded cavity corners, chamfering the upstream edge, and spoilers of different types and sizes. Rounding-off the cavity edges is found to increase the pulsation amplitude substantially, but the resonance lock-on range is delayed, i.e., it is shifted to higher flow velocities. Similarly, chamfering the upstream corner delays the onset of resonance, but maintains its intensity in comparison with that of sharp edges. Spoilers, or vortex generators, added at the upstream edge have been found to be the most effective means to suppress the resonance. However, the minimum spoiler size which is needed to suppress the resonance increases as the cavity size becomes larger.

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Figures

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Fig. 1

Geometry of the test section and parameters of the axisymmetric cavity together with the locations of pressure transducers

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Fig. 2

Axial distribution of acoustic pressure decay of the first diametral mode (m = 1) for three cavities of the same length (L/D = 2/12) but different depths (h/D = 1/12, 2/12, 4/12); x is the streamwise distance measured from the cavity center [1]

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Fig. 3

Leading edge suppression techniques: (a) base case with no modification, (b) edge rounding, (c) chamfer, and (d) saw-tooth spoiler

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Fig. 4

Schematic of the saw-tooth spoiler (dimensions are in mm)

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Fig. 5

Dimensions of the curved spoiler (dimensions are in mm)

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Fig. 6

Dimensions and orientation of the delta spoilers (dimensions are in mm)

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Fig. 7

Photographs of (a) curved spoiler and (b) delta spoiler

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Fig. 8

Aeroacoustic response of base case B3 with sharp edges; L/h = 1, h/D = 2/12

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Fig. 9

Effect of the chamfer and rounding-off the edges on the acoustic resonance of base case B3; L/h = 1, h/D = 2/12

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Fig. 10

Acoustic pressure verses reduced velocity showing the effect of chamfer and rounding-off the edges on the acoustic resonance of base case B3; L/h = 1, h/D = 2/12

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Fig. 11

Effects of chamfers on the resonance of base case B4; L/h = 2, h/D = 2/12

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Fig. 12

Effect of chamfer (/L ≈ 0.38) and spoiler 4 on the resonance of base case B5; L/h = 0.5, h/D = 4/12

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Fig. 13

Effect of spoilers 1 and 2 on the resonance of cavity case B3; L/h = 1, h/D = 2/12

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Fig. 14

Effect of spoiler 4 on the resonance of cavity B6; L/h = 1, h/D = 4/12

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Fig. 15

Effect of the curved and delta spoilers on the resonance of cavity B6; L/h = 1, h/D = 4/12

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Fig. 16

Pressure drop as a function of the flow velocity measured across cavity B3 without and with curved and delta spoilers

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