Fluid-elastic lock-in of a cavity shear layer instability with the modes of a submerged cantilevered beam

Kristin L. Cody, Michael L. Jonson, Martin L. Pollack, Stephen A. Hambric

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1 Scopus citations


Lock-in flow tones can occur for many different types of flow instabilities and structuralacoustic resonators at low Mach number. This paper examines the interaction between a shear layer instability generated by flow over a shallow cavity and the modes of an elastic cantilevered beam containing the cavity. A describing function model indicates that a cavity shear layer instability capable of producing lock-in with acoustic pipe resonances cannot achieve lock-in with equivalent structural beam resonances, particularly resonances of submerged structures. Fluid-elastic cavity lock-in is unlikely to occur due to the high level of damping that exists for a submerged structure, the high fluid-loaded modal mass, and the relatively weak source strength a cavity generates. Limited experimentation using pressure, acceleration, and particle image velocimetry (PIV) measurements has been performed which are consistent with the describing function model. A stronger source produced by a larger scale flow instability-separated flow over a bluff body-was able to lock-in with modes of the same submerged structure, further demonstrating that the concern for lock-in from a cavity shear layer instability is isolated to systems capable of stronger coupling or those dominated by fluid-acoustic resonances.

Original languageEnglish (US)
Article number061006
JournalJournal of Vibration and Acoustics, Transactions of the ASME
Issue number6
StatePublished - Dec 2019

All Science Journal Classification (ASJC) codes

  • Acoustics and Ultrasonics
  • Mechanics of Materials
  • Mechanical Engineering


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