IFD: An Implicit Finite-Difference Computer Model for Solving the Parabolic Equation

Abstract : A general purpose computer model, based on the implementation of an implicit finite-difference scheme, is developed for the solution of the parabolic wave equation. This model can be used to predict acoustic propagation loss in both range-independent and range-dependent environments. An important feature of the model is that it can handle arbitrary surface boundary conditions and an irregular bottom with arbitrary bottom boundary conditions. In the event that the bottom boundary conditions cannot be expressed mathematically, the model has the capability of introducing an artifical absorbing bottom such that, with the appropriate bottom attenuation, the problem becomes solvable. Another important feature of the model is that it can handle horizontal interfaces of layered media. The model is easy to use and easy to modify. Numerical test examples are included to demonstrate the capabilities of the model. (Author)