### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 5aPA12. Guided sound propagation in three-dimensional inhomogeneous moving
nonstationary fluid.

**Oleg A. Godin
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*NOAA/Atlantic Oceanogr. and Meteorol. Lab., 4301 Rickenbacker Cswy.,
Miami, FL 33149
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Sound propagation in a multicomponent fluid, parameters of which including
flow velocity as well as shape of boundaries are smooth and slowly varying
functions of time and two horizontal coordinates, is considered. No limitations
are imposed on the Mach number and the fluid parameters dependence on the
vertical coordinate other than the assumption that sound/flow synchronism
points are absent. All the processes in the fluid are assumed to be adiabatic.
The method of two-scale expansions is used to construct asymptotic development
of solutions of the set of hydrodynamic equations linearized with respect to
the wave's amplitude. The well-known ``vertical modes-horizontal rays''
approach is generalized to cover acoustic waves in nonstationary moving media.
An adiabatic invariant is found that governs the amplitude variation of a
normal mode along the corresponding space-time horizontal ray. Physical meaning
of the adiabatic invariant is analyzed. Results are compared to those of recent
studies of guided propagation in moving time-independent [O. A. Godin, DAN SSSR
320, 204--208 (1991)] and unstationary motionless fluid [A. V. Aref'ev and V.
S. Buldyrev, Akust. Zh. 40, 205--211 (1994)]. The importance of a consistent
account of medium's motion and its time dependence is demonstrated. [Work
supported by RBRF and NRC.]