Fast Field Program for Multilayered Media
NAVAL UNDERWATER SYSTEMS CENTER NEWPORT RI
Pagination or Media Count:
The Fast Field Program FFP is a technique for applying Fast Fourier Transform methods to Field theory. Interim results are presented for the FFP as it would be applied to a multilayered ocean. Earlier work on this subject has demonstrated the accuracy of the approach, but a reduction in computing time was needed to attain real time, in situ propagation estimations. A step in this direction has been made possible by the assumption that the water column is subdivided into strata within which the velocity of sound is allowed to vary exponentially with depth. The kernel of the integral expression for the pressure field is then given in terms of products of cylindrical functions, which can be calculated rapidly through the utilization of recurrence relations. Comparisons of the results of the FFP and normal mode theory are provided for both a shallow and a deep water example at low acoustic frequencies. In the latter case, consideration is given to the influence of the subbottom structure upon propagation predictions. The technique described is not the ultimate solution for real time calculations however, it does represent the fastest possible version of generating FFP predictions known to the author at this time.
- Acoustic Detection and Detectors