Coupled-mode modeling of sound propagation in range-dependent fluid-solid media

Area of Science:

• Geophysics
• Acoustics
• Computational Physics

Background:

• Wave propagation modeling in complex media is crucial for geophysical exploration and underwater acoustics.
• Existing methods often struggle with range-dependent, laterally heterogeneous environments.
• Efficient numerical techniques are needed to handle fluid-solid interfaces and complex geometries.

Purpose of the Study:

• To develop a discrete coupled-mode method for analyzing wave propagation in cylindrically symmetric fluid-solid media.
• To accurately model wave fields generated by a symmetric point source on the vertical axis.
• To handle range dependence by discretizing the medium into laterally homogeneous ring regions.

Main Methods:

• A discrete coupled-mode approach is employed, discretizing the medium into laterally homogeneous ring regions.
• Modal reflection matrices are recursively computed for inward propagation, relating outgoing and incoming normal modes.
• Outward propagation, stabilized by stored reflection matrices, determines modal expansion coefficients in each region.

Main Results:

• The method successfully computes wave fields in a range-dependent fluid-solid medium with a symmetric point source.
• Upsloping and downsloping interfaces are handled by distinct propagation equations, ensuring continuity.
• An approximate solution using asymptotic expressions for Hankel functions is presented.

Conclusions:

• The discrete coupled-mode method provides an effective tool for wave propagation analysis in complex fluid-solid environments.
• The approach accounts for back-scattering and includes source-correction factors for improved accuracy.
• This method enhances the simulation capabilities for geophysical and acoustic wave phenomena.