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

## 3pSAa3. Response of a fluid-loaded infinite plate subject to a line force
excitation in mean flow.

**Jinshuo Zhu
**

**
Sean F. Wu
**

**
**
*Dept. of Mech. Eng., Wayne State Univ., Detroit, MI 48202
*

*
*
Asymptotic formulations are derived to estimate the dynamic response of a
fluid-loaded infinite plate subject to a line force excitation in mean flow.
Analysis shows that mean flow may have significant effects on the plate
flexural waves when the excitation frequency is above the plate coincidence
frequency, moderate effects around the coincidence frequency, and little
effects below the coincidence frequency. This is because at high frequencies,
most of plate vibration energy is converted to acoustic energy. Since mean flow
can greatly modify the radiated acoustic pressure, the effect of mean flow on
plate flexural vibration becomes obvious. At low frequencies, there is no sound
radiation and most of plate vibration energy stays close to the surface.
Consequently, the effect of mean flow on plate vibration is greatly reduced.
The asymptotic behaviors of the branch cut integrals at large distances from
the point of excitation are also investigated. It is shown that the leading
terms of the branch cut integrals decay with distances along the plate surface.
The presence of mean flow suppresses the amplitude of the disturbance
propagating in the upstream direction, but enhances that of the disturbance
propagating in the downstream direction. [Work supported by ONR.]