An Investigation of Shallow Water Acoustic Propagation through a Tidal Internal Wave Field

摘要

The impact of internal waves on shallow water acoustic propagation has been drawing much effort during past decades. Besides many experiments have been operated, more numerical simulations were conducted due to their extensive feasibility. But so many simulations considered internal wave environment by using the solution of an ideal model, such as KdV equation. In this study, a non-hydrostatic ocean model, in which the open boundary forcing can be set by considering single or combined internal wave mode, was used to generate the internal wave field at the M2 tidal frequency. The topographic and initial oceanographic data were come from the experiment of AEYSFI 2005. The acoustic transmission between 300-900Hz is computed over the subset of 22km range. The acoustic field structure is similar by combining interval wave mode 1, 2, mode 1,2,4 or mode 1, 3, 4 (group 1) as external forcing, there are another similar acoustic field structure for mode 1,2,4 or mode 1,2,3,4 forcing (group 2), finally mode 1 forcing (group 1). Different acoustic normal mode coupling occurred due to the different combination of internal wave mode forcing. The acoustic field variability is dependent not only on the source depth and source frequency, but also on the combination of internal wave. Even the parameters of internal wave mode are modified gently, the acoustic mode coupling become quite different.