Accession Number : ADA138946

Title :   A New Eigenfunction Expansion and Its Application to Waveguide Acoustics.

Descriptive Note : Interim technical rept. 15 Jun-15 Dec 83,


Personal Author(s) : Pannantoni,R F

PDF Url : ADA138946

Report Date : 15 Feb 1984

Pagination or Media Count : 33

Abstract : This report describes the application of new eigenfunction expansions to the analysis of sound propagation in a two-dimensional waveguide. One boundary of the waveguide is flat, the other boundary is uneven, and the waveguide is filled with inhomogeneous, lossless fluid. The expansions accomodate the conditions that the pressure vanish at the flat boundary and that the normal component of fluid velocity vanish at the uneven boundary. The method of expansion is novel in that two essentially independent functions are expanded simultaneously. Expansions of this kind provide a complete representation of the exact pressure and velocity fields at the boundaries of the waveguide as well as in the fluid. Conditions at the uneven boundary can be satisfied because the eigenvalue problem that generates the expansion functions has a boundary condition that contains the eigenvalue. The eigenvalues are therefore complex even though the waveguide is lossless. The coefficients in the field expansions vary along the direction of propagation.

Descriptors :   *Acoustic waves, *Wave propagation, *Waveguides, Eigenvalues, Boundary value problems, Sound transmission, Losses, Theorems

Subject Categories : Numerical Mathematics

Distribution Statement : APPROVED FOR PUBLIC RELEASE