The Numerical Solution of Underwater Acoustic Propagation Problems Using Finite Difference and Finite Element Methods
Abstract
This report discusses various aspects of the numerical solution of underwater acoustic wave propagation problems. In the first part of the report, a model propagation problem based on the two-dimensional Helmholtz equation with a variable sound speed is considered. A finite element computer code for solving such problems was implemented at NRL on the VAX 11/780. A distinctive feature of the code is the implementation of a recently developed iterative method for solving the resulting large, sparse, indefinite, non-self-adjoint system of equations. This allowed for the efficient solution of over 35,000 complex equations on a relatively small computer. Some of the results obtained after applying this code to the model problem are described. Furthermore, additional modifications that can be made to the code to improve its efficiency and extend its applicability to more general propagation models are discussed. In the second part of this report, the general situation of the coupled acoustic/ elastic wave equation in two and three dimensions is considered. For example, this may correspond to an ocean environment in which there is ice on the surface as well as an irregularly shaped bottom structure. Finite difference and finite element methods for solving both the time harmonic and time dependent models are discussed. Various issues are considered that are important in determining the size of the problem that can be adequately treated. This includes the computer power as well as the mathematical and modeling techniques available.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 09, 1984
- Accession Number
- ADA143968
Entities
People
- C. I. Goldstein
Organizations
- United States Naval Research Laboratory