ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pUW4. Modeling range-dependent propagation using trapped and leaky wedge modes.

John A. Fawcett

SACLANT Undersea Res. Ctr., Viale San Bartolomeo, 400, 19038 La Spezia, Italy

Evan K. Westwood

Appl. Res. Labs., Univ. of Texas, Austin, TX 78713-8029

Christopher T. Tindle

Univ. of Auckland, Auckland, New Zealand

The use of coupled wedge modes in modeling range-dependent underwater acoustic propagation has been previously described by Primack and Gilbert [H. Primack and K. E. Gilbert, 3254--3262 (1991)]. Their approach has been extended by using leaky modes, in addition to the trapped ones, in wedge mode computations. Trapped modes decay exponentially in the basement and correspond, in terms of rays, to angles of propagation which are totally internally reflected above the basement interface; leaky modes are not well behaved in the basement, but provide an excellent discrete approximation to the continuous spectrum contribution in the water column. Because leaky modes are included in the computations, it is possible to model accurately shallow water environments where trapped/leaky mode conversions are important. Within a single wedge domain, adiabatic wedge mode theory is used for computations; at wedge junctures, a least-squares mode coupling scheme is employed. Numerical examples where the results of the coupled wedge mode method are compared to parabolic equation and standard adiabatic mode computations are presented.