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Acoustic Response of Multiple Shallow Cavities: Effect of Separation Distance
Ayman A. Shaaban, Samir Ziada

Last modified: 2018-04-14

Abstract


Flow over ducted shallow cavities can excite fluid resonant oscillations. These resonances often generate noisy environment at the work place and may eventually lead to structure failure of associated equipment. A common industrial application is the flow in corrugated pipes that can be modelled as a series of consecutive shallow cavities. In the current study, the effect of the separation distance on the aeroacoustic source of multiple shallow cavities is investigated. The source is measured using the Standing Wave Method (SWM) where two sets of three microphones are equipped, upstream and downstream of the cavities section, to measure the discontinuity in the acoustic pressure generated by the flow over the cavities. Two and three-cavity configurations are tested with a separation-to-cavity length ratio in a practical range from 0.5 to 1.375. At low and intermediate sound levels, extremum spacing ratios of 0.5 and 1.375 show constructive interference with high source values. However, at high excitation levels, 10% and higher, the source strength becomes inversely proportional to the separation distance. These findings are observed in both the double and triple-cavity configurations. On the other hand, the destructive interference spacing ratio is shown to be a function of the number of cavities.


Keywords


multiple cavities; aeroacoustic source; fluid structure interaction; flow-sound interaction

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