Title: The dynamics of low-frequency signal acoustic intensity vector vortex structure in shallow sea

Author(s): V. A. Shchurov

Affiliation(s): Federal State Budgetary Scientific Institution V.I.Il' ichev Pacific Oceanological Institute, Far East Branch of the Russian Academy of Sciences

Abstract: Spatiotemporal vector and phase properties of interference field of low-frequency signalling tone between three local vortices in a real shallow sea wave-guide have been studied. It has been demonstrated that in the field of constructive interference, components of particle velocity field and acoustic pressure are coherent. As a consequence the transfer of signal energy along the axis of a shallow sea wave-guide is accomplished with plane wave. Physical objects are detected in the field of destructive interference, which, according to known deterministic signs, can be defined as local vortices of the intensity vector. A large-scale vorticity with acoustic intensity vector curl, components different from zero originates in the vicinity of local vortices. Regular particle displacements of local vortices have been detected against combined receiving device phase centre along the axis of a wave-guide. It has been demonstrated that the structure of vortices depends on signal/noise ratio. Local vortices and vorticity form vortex structure of vector acoustic field. Signalling tone with frequency of 88 ± 1 Hz from near-surface moving sound source was taken into consideration. Introduced results of full-scale experiment expand our concepts of real fundamental properties of shallow sea acoustic field and are to be considered in theoretical models.