ASA 126th Meeting Denver 1993 October 4-8

4pSA3. Scattering of waves from ribs on fluid-loaded plates.

Zhang Wang Andrew Norris

Dept. of Mech. & Aerosp. Eng., Rutgers Univ., P.O. Box 909, Piscataway, NJ 08855-0909

A new formulation of the Green's function for a fluid-loaded infinite plate under line loading is presented. The Green's function is expressed explicitly in terms of a sum of the five free modes of propagation plus a semi-infinite integral. The Green's function itself and its first and second derivatives at the loading line are obtained in analytic forms that prove to be useful in computing the scattering matrix for a rib on the plate. The scattering matrix for an isolated rib is derived. It is shown that the wave incident onto one of the n-arbitrary ribs on the plate can be written as a product of the original incident wave and a matrix, referred to as the influence matrix, which reflects the alteration of the incident wave on one rib produced by the presence of the other ribs. The influence matrix is an inverse of a matrix whose elements are the scattering matrices for single ribs and unit matrices, and it can be expanded as an infinite series which converges rapidly. Each term in the infinite series may be interpreted as a generalized ray. Numerical results are presented and compared with previous work. [Work supported by ONR.]