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.