Theory and Application of Scattering from an Object in an Ocean Waveguide

摘要

A method was developed to describe acoustical scattering from an object in awaveguide by using normal mode theory to describe the incident field. Each mode is decomposed at the object into a pair of upgoing and downgoing plane waves. A transition matrix was used (developed via the extended boundary condition method of Waterman) to determine the resulting near-field scattered field. The far-field scattered field was determined by invoking Huygens' principle. This far-field solution satisfies all boundary conditions and preserves continuity of the solution throughout all space. The examples show that the object is correctly coupled to the waveguide. This was done by showing that the object's scattered field acts as a secondary source and that this scattered field obeyed the same boundary conditions as the point source field. This method of determining the scattered field from a three-dimensional object allows one to determine not only the correct target strength (intensity), but also to properly determine the phase. In addition this method allows the investigation of the interaction between the incident field and the waveguide, the incident field with the object, and the object's scattered field with the waveguide. In this manner a better understanding of the ongoing physical processes can be obtained.