A hybrid approach for simulating fluid loading effects on structures using experimental modal analysis and the boundary element method

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Abstract

Many structural acoustics problems involve a vibrating structure in a heavy fluid. However, obtaining fluid-loaded natural frequencies and damping experimentally can be difficult and expensive. This paper presents a hybrid experimental-numerical approach to determine the heavy-fluid-loaded resonance frequencies and damping of a structure from in-air measurements. The approach combines in-air experimentally obtained mode shapes with simulated in-water acoustic resistance and reactance matrices computed using boundary element (BE) analysis. The procedure relies on accurate estimates of the mass-normalized, in vacuo mode shapes using singular value decomposition and rational fraction polynomial fitting, which are then used as basis modes for the in-water BE analysis. The method is validated on a 4.445 cm (1.75 in.) thick nickel-aluminum-bronze rectangular plate by comparing natural frequencies and damping obtained using the hybrid approach to equivalent data obtained from actual in-water measurements. Good agreement is shown for the fluid-loaded natural frequencies and one-third octave loss factors. Finally, the limitations of the hybrid approach are examined.

Original languageEnglish (US)
Pages (from-to)3073-3080
Number of pages8
JournalJournal of the Acoustical Society of America
Volume138
Issue number5
DOIs
StatePublished - Nov 1 2015

All Science Journal Classification (ASJC) codes

  • Acoustics and Ultrasonics
  • Arts and Humanities (miscellaneous)

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