ASA 124th Meeting New Orleans 1992 October

5aSA6. The spatial and temporal response of fluid-loaded, line-driven panel structures.

T. J. Wahl

J. S. Bolton

Ray W. Herrick Labs., School of Mech. Eng., Purdue Univ., West Lafayette, IN 47907

In this paper wave propagation is considered in and near fluid-loaded, line-driven panel structures in several configurations. In one configuration, for example, the driven panel is separated from a second panel by a finite-depth, fluid-filled space. In a second case, wave propagation in fluid-loaded, ribbed panels is considered. In both those cases, solutions for the spatial and temporal distributions of the panel velocity as well as the acoustic particle velocity and sound pressure in the adjacent fluid can be obtained by using wave-number transform techniques. The inversion integral that defines the spatial response in the frequency domain may then be evaluated by using the fast Fourier transform algorithm. Subsequently, the temporal response may be obtained by performing an additional inverse Fourier transform. Having obtained the pressure and velocity solutions it is a straightforward matter to compute both the instantaneous and time-averaged intensity in the fluid adjacent to the structure. By examining the latter quantities the flow of acoustic energy from the radiating structure to the fluid and vice versa may easily be visualized. Examples will be given in which energy is shared between the driven panel and a number of different modes in the adjacent fluid space, and the existence of multiple coincidence frequencies in that case will be illustrated. In addition, conversion of subsonic panel wave motion into radiating components at line discontinuities will be considered.