### ASA 127th Meeting M.I.T. 1994 June 6-10

## 3pSAa1. Sound radiation from two semi-infinite dissimilar plates subject
to a harmonic line force excitation in mean flow. Part I: Theory.

**Sean F. Wu
**

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Jinshuo Zhu
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**
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*Dept. of Mech. Eng., Wayne State Univ., Detroit, MI 48202
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Formulations are derived for predicting sound radiation from two
semi-infinite dissimilar plates subject to a line force excitation at the joint
in the presence of mean flow using the Wiener--Hopf technique and Fourier
transformations. The acoustic pressure is solved in the wave-number domain
first and expressed in terms of decomposition factors and eight parameters
associated with displacements, slopes, bending moments, and shear forces at the
joint of two plates. The decomposition factors are evaluated via contour
integrations, and eight parameters are determined by a set of simultaneous
equations derived from boundary conditions and the finiteness requirement
imposed on the joint. It is shown that the set of equations reduces to a 2x2
matrix for a welded joint, a 3x3 matrix for a hinged joint, and a 4x4 matrix
for a free--free joint, i.e., two plates being mechanically unconnected. The
frequency-domain acoustic pressure is subsequently obtained by taking an
inverse Fourier transformation, and expressed as a sum of residues enclosed by
a deformed contour plus contributions from integrations along the branch cut.
Asymptotic behaviors of the plate flexural displacement and acoustic pressure
in the frequency-wave-number domain are obtained. Effects of mean flow on
resulting sound radiation are examined. [Work supported by ONR.]