Acoustic and Vibration Fields Generated by Ribs on a Fluid-Loaded Panel. I. Plane-Wave Problems for a Single Rib.
LEEDS UNIV (ENGLAND) DEPT OF APPLIED MATHEMATICAL STUDIES
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This paper presents an analytical study of the interaction between incident wave fields and a single rib on fluid-loaded panel. The panel is modeled as an infinite membrane with frequency dependent tension to partially simulate the dispersion characteristics of a thin elastic plate, and the incident waves are taken as plane structural or acoustic waves at normal and oblique incidence on the rib. Our principal concern is with the structural wave field transmitted across the rib in the case of the infinite mechanical impedance and finite nonlocal rib impedance though the nonspecular acoustic field scattered by the panel-plus-rib is also examined. Matched asymptotic expansions are used to construct analytical approximations covering the entire frequency range, utilizing the smallness of a fluid-loading-at-coincidence parameter. The analytical results recover numerical results obtained elsewhere in appropriate regions of parameter space, complement them by providing simple approximations in those regions typically of rapid variation or of heavy fluid loading where numerical methods are difficult to implement, and reveal the physical aspects of fluid loading in effecting energy transfer across ribbed structures. Author