Research On The Algorithm Of Coupled Mode Method Of Acoustic Field

Many theoretical and computational models are presented for sound propagation inseawater, characterized by constant or slowly changed horizontal medium, however, for thosewith evidently changed horizontal medium, the effect on acoustic field should be taken intoconsideration. Combined with the current coupled mode theory of high precision, the coupledmode-parabolic equation theory is applied to calculate acoustic field with changed horizontalmedium.This article focuses on the theoretical derivation and solving a detailed study anddiscussion on the horizontally changed waveguide with the coupled normal mode-parabolicmethod (CMPE).Moreover, derived in detail in the symmetric case of two-dimensionalcylindrical coordinate, the CMPE theory and coupling coefficient representation is employedto facilitate numerical calculation. Besides, on the basis of two-dimension, a brief derivationis performed in the CMPE theory.In cylindrical coordinate system, the CMPE theory is deduced directly in the situationthat density changes. For that density is weakly range-dependent or only varies in the verticaldirection, by simplifying the coupling coefficient, CMPE sound pressure expression isobtained correspondingly. By means of the parabolic equation, utilizing the couplingcoefficient above, the corresponding expressions of amplitudes of normal modes is available.Calculating procedures of Coupled Normal Mode-Parabolic Equation Method areprogrammed using FORTRAN language. Through comparing with the Couple07results,reasons of error exist in three aspects: not enough orders of Krakenc calculation are called; theprocess of calculating the eigenvalue and eigenfunction is not as accurate; step approachmethod introduces errors inevitably.