Normal-Mode and Phase-Integral Methods for Determining Phase and Group Velocities in Simple Underwater Acoustic Ducts
Abstract
This theoretical report compares normal-mode and phase-integral results for three simple classes of ducts. These classes are a positive-gradient half space bounded above by a free or a rigid surface and an unbounded refractive duct. The major interest in these simple ducts is that the analysis leads to the concept of canonical eigenvalues. The term 'canonical' is used because the eigenvalues apply to an entire class of sound-speed profile rather than to one specific profile as in the customary eigenvalue approach. The general canonical eigenvalue equation contains two dimensionless mathematical variables and a set of dimensionless coefficients that are functions of the profile parameters. The normal-mode and phase-integral results for unbounded refractive ducts are compared with modal results for a double-duct profile with two refractive ducts. Modal results for the two models agree when the double- duct phase velocities of adjacent modes are well separated. Keywords: Acoustic channels; Acoustic refraction/velocity; Acoustic propagation; Wave propagation; Normal modes; Group velocities.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1990
- Accession Number
- ADA221393
Entities
People
- D. Gordon
- F. Hosmer
- M. A. Pedersen