The KRAKEN normal mode program

Abstract

In the late 1970's several normal-mode models existed which were

widely used for predicting acoustic transmission-loss in the ocean; however, each had its own problems. Typical difficulties included numerical instabilities for certain types of sound-speed profiles and failures to compute a complete set of ocean modes. In short, there was a need for a model that was robust,

accurate, and efficient. In order to resolve these problems a new algorithm was developed forming the basis for the KRAKEN normal mode model. Over subsequent years, KRAKEN was greatly extended, with options for modeling ocean environments that are range-independent, range-dependent or fully 3-dimensional. The current version offers the specialist a vast number of options for treating ocean-acoustics problems (or more generally acoustoelastic waveguides). On the other hand, it is easy for a less sophisticated user to learn the small subset of tools needed for the common problem of transmission-loss moddeling in range-independent ocean environments. This memorandum addresses the need for a more complete user's guide to supplement the on-line help files. The first chapters give a fairly technical description of the mathematical and numerical basis of the model. Additional chapters give a simpler description of its use and installation in a manner that is accessible to less scientifically-oriented readers.