ASA 125th Meeting Ottawa 1993 May

3aSA3. The role of acoustic coupling on the radiation from a vibrating source.

Lucio Maestrello

NASA Langley Res. Ctr., MS 463, Hampton, VA 23681-0001

Abdelkader Frendi

Analytical Services and Mater., Inc., Hampton, VA 23369

Alvin Bayliss

Northwestern Univ., Evanston, IL 60201

The response of an acoustically excited flexible surface together with the resulting sound radiation was considered. A model was employed that accounts for the full coupling between the surrounding fluid and the vibrating surface in three dimensions as well as two dimensions. The model couples the nonlinear Euler equations with an equation describing the nonlinear vibration of the plate. Different regimes of plate vibration and acoustic radiation were described, including linear, nonlinear, quasiperiodic, and apparently chaotic dynamics. It was found that, in the linear regime, the effect of the fluid/structure coupling is not significant. In the nonlinear regime, the effect of the coupling is to significantly reduce the harmonic content in both the plate vibration and the acoustic field. Furthermore, the nonlinear radiation exhibits a relative increase in harmonic content and an overall reduction in level as the acoustic propagation distance increases.