A Super-Algebraically Convergent, Windowing-Based Approach to the Evaluation of Scattering from Periodic Rough Surfaces

Citation

Monro, John Anderson (2008) A Super-Algebraically Convergent, Windowing-Based Approach to the Evaluation of Scattering from Periodic Rough Surfaces. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/F9VM-JP39. https://resolver.caltech.edu/CaltechETD:etd-01032008-222910

Abstract

We introduce a new second-kind integral equation method to solve direct rough surface scattering problems in two dimensions. This approach is based, in part, upon the bounded obstacle scattering method that was originally presented in Bruno et al. [2004] and is discussed in an appendix of this thesis. We restrict our attention to problems in which time-harmonic acoustic or electromagnetic plane waves scatter from rough surfaces that are perfectly reflecting, periodic and at least twice continuously differentiable; both sound-soft and sound-hard type acoustic scattering cases---correspondingly, transverse-electric and transverse-magnetic electromagnetic scattering cases---are treated. Key elements of our algorithm include the use of infinitely continuously differentiable windowing functions that comprise partitions of unity, analytical representations of the integral equation’s solution (taking into account either the absence or presence of multiple scattering) and spectral quadrature formulas. Together, they provide an efficient alternative to the use of the periodic Green’s function found in the kernel of most solvers’ integral operators, and they strongly mitigate the rapidly increasing computational complexity that is typically borne as the frequency of the incident field increases.

After providing a complete description of our solver and illustrating its usefulness through some preliminary examples, we rigorously prove its convergence. In particular, the super-algebraic convergence of the method is established for problems with infinitely continuously differentiable scattering surfaces. We additionally show that accuracies within prescribed tolerances are achieved with fixed computational cost as the frequency increases without bound for cases in which no multiple reflections occur.

We present extensive numerical data demonstrating the convergence, accuracy and efficiency of our computational approach for a wide range of scattering configurations (sinusoidal, multi-scale and simulated ocean surfaces are considered). These results include favorable comparisons with other leading integral equation methods as well as the non-convergent Kirchhoff approximation. They also contain analyses of sets of cases in which the major physical parameters associated with these problems (i.e., surface height, wavenumber and incidence angle) are systematically varied. As a result of these tests, we conclude that the proposed algorithm is highly competitive and robust: it significantly outperforms other leading numerical methods in many cases of scientific and practical relevance, and it facilitates rapid analyses of a wide variety of scattering configurations.

Thesis Files