### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 2pUW9. Horizontal refraction of 3-D curvilinear wedge modes.

**Peter C. Mignerey
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*Acoust. Div. 7120, Naval Res. Lab., Washington, DC 20375
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For shallow-water acoustic propagation, the wavelength is commensurate with
the water depth but short compared to the horizontal extent of the problem.
Under these conditions a sloping bottom causes the development of normal modes
having wavefronts that are curved in the vertical direction. For simple slopes,
such wedge modes have been shown to propagate with cylindrical wavefronts along
characteristics in the horizontal plane. This work extends adiabatic wedge mode
theory to regions of arbitrary bathymetry by constructing a three-dimensional
curvilinear coordinate system that follows the contours of the ocean bottom. The
requirement for separation of the depth coordinate from the coupled horizontal
coordinates produces a nonlinear differential equation for a potential field.
The gradient of this field then gives the depth scale factors and curved shape
of the wedge modes. A standard normal mode problem is then solved to obtain the
curvilinear wedge modes and a ray-trace method is used to study the horizontal
motion of those modes. An overview of the model formulation and some examples
will be presented.