### ASA 126th Meeting Denver 1993 October 4-8

## 5aUW5. Long-range acoustic propagation in four dimensions.

**Gregory J. Orris
Michael D. Collins
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*Naval Res. Lab., Washington, DC 20375
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Ocean acoustic modeling is usually restricted to frequency-domain problems
in two dimensions. Since ocean acoustics problems typically involve domains
that are very large relative to a wavelength, computation times often become
prohibitive when a third dimension (either time or the third spatial variable)
is included. The adiabatic mode parabolic equation (PE), which has been applied
to solve global-scale problems in three spatial dimensions [Collins et al., J.
Acoust. Soc. Am. 93, 2321 (1993)], is practical for solving four-dimensional
problems out to long range (i.e., hundreds of wavelengths or more). In the time
domain, the adiabatic mode PE solution illustrates the flow of energy in the
modal coefficients, which depend on range and azimuth.