ASA 124th Meeting New Orleans 1992 October

3aSA9. Approximations for the 2-D Green's function of a fluid-loaded plate.

Douglas M. Photiadis

Naval Res. Lab., Washington, DC 20375-5000

Simple analytical formulas to predict the acoustic component of the 2-D Green's function of a fluid-loaded plate are presented. The formulas do not require any side computations such as numerical zero finding or numerical integrations. The simplest result obtained provides a good estimate of the Green's function for a very broad range of frequencies, being degraded only near the coincidence frequency. A somewhat more complicated formula, almost uniformly valid in frequency, and yielding reasonable accuracy even at coincidence, is also presented. Numerical results comparing the asymptotic approximations to the ``exact'' Green's function are presented, and show significant improvement over a basic steepest descents-based approximation. For large values of x, very high accuracy can be achieved with relative errors of less than 0.1%. For other less stringent applications, the approximations are accurate to within 10% at fairly small distances from the source, requiring only k[sub f]x>1 and k[sub 0]x>0.5.