ASA 127th Meeting M.I.T. 1994 June 6-10

3aUW2. A sloping-boundary condition for PE calculations in range-dependent acoustic media.

Gary H. Brooke

Defence Res. Establishment Pacific, FMO Victoria, BC V0S 1B0, Canada

Philip M. Wort

MacDonald Dettwiler and Assoc. Ltd., 13800 Commerce Pkwy., Richmond, BC V6V 2J3, Canada

The traditional one-way parabolic equation (PE) formulation for range-dependent layered acoustic media is modified to include effects associated with the boundary conditions along a sloping interface. Essentially, the boundary condition for continuity of the normal derivative of pressure along a sloping interface can be cast in an approximate form which does not depend on range but does contain terms up to second order in the derivatives with respect to depth. The new sloping-boundary condition is then applied along an ``equivalent'' horizontal interface within each range-independent step of the PE. Numerical results obtained for the ASA benchmark-wedge problem are used to test the new approach against an accurate two-way PE algorithm. Good agreement in this case suggests that the sloping-boundary condition, incorporated into a one-way PE, can lead to an efficient and accurate alternative to forward calculations using two-way PE.