Kraken Program for Acoustic Field Computation Using the Normal Mode Method

The normal mode method is a widely used numerical technique for underwater acoustic field modeling, particularly suitable for calculating sound wave propagation characteristics in marine environments. The Kraken program serves as a classic computational tool based on the normal mode method, efficiently simulating sound wave propagation through water columns and seabed structures. It provides critical support for underwater acoustic research and engineering applications through its robust numerical implementation.

The core algorithm of Kraken employs normal mode expansion technology, decomposing the acoustic field into a series of independent modes where each mode represents a specific propagation pattern under given environmental conditions. The program computes eigenvalues and eigenfunctions for these modes by solving the Helmholtz equation through numerical discretization techniques. This enables calculation of propagation loss, phase variations, and other acoustic parameters at different depths and distances, implemented via matrix operations and boundary condition handling in the code.

Kraken's computational framework accommodates diverse marine environments including stratified media, sloping terrains, and complex seabed structures. Its high computational efficiency stems from optimized eigenvalue solvers and mode summation algorithms, making it particularly suitable for low-frequency acoustic propagation problems. The program finds important applications in sonar system design, marine bioacoustics research, and underwater communication systems through its configurable environmental parameter inputs.

The program's advantages lie in its numerical stability and flexible adaptation to environmental parameters, though computational accuracy is influenced by normal mode truncation order. Practical implementations require careful parameter tuning through convergence tests to balance precision and computational cost, with the code allowing adjustable mode counts and depth resolution settings for optimal performance.