Results from a simulation study of mode coupling due to acoustic wave-soliton interactions

Abstract

There is a strong interest in understanding the interactions between ocean acoustic waves and shallow water solitons. Central to these interactions are the acoustic mode conversions caused by the solitons. Such mode conversions potentially occur each time the acoustic wave and soliton interact; however, at certain combinations of acoustic-oceanographic wavelengths, the interactions can produce large losses in acoustic signal. Mode coupling results will be discussed from simulation studies that examined the signal loss due to interactions with solitons in the Strait of Messina. Coupled mode formulations were avoided so that interpretations of results were not dependent upon any particular mode coupling scheme. Rather, the full-wave, two-way, finite-element model, FFRAME, was used to produce numerically accurate predictions of the complex pressure field as it passed through the soliton. This complex field was then decomposed into its component wave numbers via an FFT to determine the mode structure. This simulation included the entire acoustic field (forward propagation, backscatter, multiple scatter, etc.). The results were realistic and difficult to interpret. Results will be shown at various points along the way as the acoustic wave passed thorugh the soliton. [Work supported by ONR/NRL and by a High Performance Computing DoD grant.]