### ASA 125th Meeting Ottawa 1993 May

## 3aSA2. Mean flow effects on the vibroacoustic behavior of baffled plates
in heavy fluids.

**Franck Sgard
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*G.A.U.S, Genie Mecanique, Univ. of Sherbrooke, Sherbrooke, PQ J1K 2R1,
Canada
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**Noureddine Atalla
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*University of Sherbrooke, Sherbrooke, PQ J1K 2R1, Canada
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The originality of the present paper lies on the development of a
formulation accounting for mean flow effects in the vibroacoustic model of a
baffled plate. The importance of those effects on the vibrational behavior and
stability of a baffled plate with arbitrary boundary conditions, as well as its
acoustic radiation pattern, is assessed. The analysis is based on a
finite-element method for the calculation of the plate transverse vibrations
and the use of the extended Kirchhoff's integral equation to account for fluid
loading with mean flow. A boundary-element method is used to compute the
acoustic radiation impedance. The formulation shows explicitly the effects of
mean flow in terms of added mass, stiffness, and radiation damping.
Furthermore, the added stiffness is shown to be responsible for the
instabilities that occur as the flow speed increases. Details of the
formulation as well as its numerical implementation are exposed and results
showing the effect of the mean flow on the different vibroacoustic indicators
(mean square velocity, radiated acoustic power, modal radiation efficiencies)
are presented.