ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

2aSA6. Analytical numerical matching for efficient calculation of acoustic scattering from cylindrical shells.

Richard C. Loftman

Donald B. Bliss

Mech. Eng. and Mater. Sci., Duke Univ., Box 90300, Durham, NC 27708

Structural discontinuities in highly coupled fluid/structure systems are modeled by a novel approach called analytical numerical matching (ANM). ANM separates the low-resolution global influence of a discontinuity from the relatively high-resolution local effects. A continuous, smoothed replacement for a fundamental structural discontinuity is constructed so that the system is identically unchanged beyond a small smoothing region. Simultaneously, the precise local effect of smoothing the discontinuity is retained in analytical form. The smoothed problem is solved by numerical techniques, with rapid convergence and reduced computational cost. The original discontinuous character is restored, using the analytical expression for the local difference between the smoothed and the original problems. ANM has been successfully applied to acoustic scattering from a thin, infinitely long cylindrical shell, with multiple structural discontinuities. Local solutions for line discontinuities with radial, tangential, and rotational constraints have been formulated using ANM. Line constrained scattering problems, as well as line driven problems, are investigated. The ability of analytic numerical matching to replace a discontinuous physical problem by a well-behaved continuous one for numerical evaluation, while ultimately retaining the original geometry and physical behavior, is illustrated. [Work supported by ONR.]