Andrew N. Norris
Dept. of Mech. Eng., Rutgers Univ., Piscataway, NJ 08855-0909
This talk surveys some key developments in modeling the acoustic response of fluid-loaded structures. Recent experimental and computational results indicate that wave interaction effects are very significant for structures with even a small degree of complexity. The complexity can be as simple as a few ribs or stiffeners which convert supersonic membrane-type wave motion into subsonic flexural energy, and vice versa. A great deal of effort continues to be put into developing efficient numerical methods in order to simulate greater complexity. At the same time, recent analytical findings have increased our understanding of the dynamic interaction at ribs and plate junctions, in terms of wave-like diffraction processes. Ray methods have been developed to handle the multi-wave nature of structural energy flow on nonseparable shapes, and provide a fast numerical method for dealing with high-frequency simulation. In general, the complexity of the substructures within the relatively well-defined ``master'' structure presents the most difficult challenge for modelers. Techniques are only now being developed to distinguish these effects in a logical manner. One approach of great interest is ``fuzzy'' structural acoustics. The idea is to replace the detailed dynamics of the internal by a smeared out effect, which still contains some of the physics of the internal such as the total mass, and the modal density per unit bandwidth. Fuzzies are also ``hot'' in that they are guaranteed to generate thermal energy among ASA participants concerned about energy effects.