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

## 2pUW12. Finite difference simulations of propagation in a shallow water
environment.

**John B. Schneider
**

**
Shira Lynn Broschat
**

**
Patrick J. Flynn
**

**
**
*School of Elec. Eng. and Comput. Sci., Washington State Univ., Pullman, WA
99164-2752
*

*
*
The propagation of acoustic energy in a shallow water environment is
studied using a two-dimensional, staggered-grid finite-difference model. Such a
model allows one to view the propagation of energy in the time domain
throughout the region of interest. Since fields are available ``everywhere,''
the model can be used to guide the development of robust schemes for the
detection of scatterers in the water column or buried in the sediment. In
addition, it can be used to benchmark approximate models for acoustic
propagation and scattering in shallow water. This paper considers the effect of
different physical features on the possible identification of scatterers. Such
scattering mechanisms as top and bottom roughness and inhomogeneities in the
water column are considered. Monte Carlo simulations are used to gauge the
relative effects of these features. Frequencies on the order of 7.5 kHz are
considered for depths up to 30 m. The implementation used here includes several
enhancements over traditional finite-difference models. For example, typical
finite difference models approximate continuously varying material interfaces
by an interface that appears like a staircase---the material properties change
only at discrete location. For this research a conformal technique is used to
model more accurately the continuous interface. [Work supported by ONR.]