Broadband modeling of downslope propagation in a penetrable wedge

2008

J. Comp. Acous.

A coupled-mode formalism based on complex Airy layer mode solutions is presented. It is an extension into the complex horizontal wavenumber plane of the companion article [Stotts, J. Acoust. Soc. Am. 111 (2002) 1623-1643, referred to here as the real horizontal wavenumber version, which accounted for general ocean environments but was restricted to normal modes on the real horizontal wavenumber axis. A formulation of the expressions for both trapped and continuum complex coupling coefficients is developed to dramatically reduce computer storage requirements and to make the calculation more practical. The motivation of this work is to demonstrate the numerical implementation of the derivations and to apply the method to an example benchmark. Differences from the real horizontal wavenumber formalism are highlighted. The coupled equations are solved using the Lanczos method [Knobles, J. Acoust. Soc. Am. 96 (1994) 1741-1747. Comparisons of the coupled-mode solution to a parabolic equation solution for the ONR shelf break benchmark validate the results.

Section: Introductionmentioning

confidence: 98%

Two-Way Coupled-Mode Solutions in the Complex Horizontal Wavenumber Plane

2008

J. Comp. Acous.

“…Previously, the two-way integral equation coupled-mode (IECM) approach has proved successful, when an adiabatic approach is not applicable, in producing benchmark solutions of the total pressure field as a function of range in the forward direction for large scale, i.e., smooth, range-dependent boundaries that result in forward-and back-scattering from mode coupling. [3][4][5][6] The goal of this paper is to establish a benchmark solution that is, in principle, an exact numerical solution for the reverberation time series for an environment with a range-dependent fine-scale rough bottom boundary that induces mode coupling and generates a scattered field. The solution includes scattering effects to all orders, i.e., sums the infinite series of forward and backward contributions at each range point and maintains energy conservation.…”

Section: Introductionmentioning

confidence: 99%

Scattering in a Pekeris waveguide from a rough bottom using a two-way coupled mode approach

The Journal of the Acoustical Society of America

Knobles

Koch

2011

Scattering from a rough ocean bottom is described numerically with a two-way coupled-mode formalism that contains scattering effects to all orders and provides an exact solution to the wave equation. Both scattered field and direct blast components are computed within the formalism framework. A comparison of the scattered component solution from the coupled mode with the Born approximation (BA) solution for scattering from a rough bottom Pekeris waveguide shows that the BA predicts correctly the scattered field levels but not detailed structure. The transition from direct blast to scattered field dominance is identified in the total field time series.

A two-way coupled mode formalism that satisfies energy conservation for impedance boundaries in underwater acoustics

The Journal of the Acoustical Society of America

Koch

2015

This paper shows that energy conservation and the derivation of the two-way coupled mode range equations can be extended in three dimensions to complex mode functions and eigenvalues. Furthermore, the energy in the coupled mode formulation is conserved for finite thickness fluid ocean waveguides with a penetrable bottom boundary beneath any range dependence. The derivations rely on completeness and a modified orthonormality statement. The mode coupling coefficients are specified solely and explicitly by the waveguide range dependence. The statement of energy conservation is applied to a numerical coupled mode calculation.