6 research outputs found
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Efficient boundary integral solution for acoustic wave scattering by irregular surfaces
The left-right operator splitting method is studied for the efficient
calculation of acoustic fields scattered by arbitrary rough surfaces. Here the
governing boundary integral is written as a sum of left- and right-going
components, and the solution expressed as an iterative series, expanding about
the predominant direction of propagation. Calculation of each term is
computationally inexpensive both in time and memory, and the field is often
accurately captured using one or two terms. The convergence and accuracy are
examined by comparison with exact solution for smaller problems, and a series
of much larger problems are tackled. The method is also immediately applicable
to other scatterers such as waveguides, of which examples are given
Random scattering by rough surfaces with spatially varying impedance
A method is given for evaluating electromagnetic scattering by an irregular
surface with spatially-varying impedance. This uses an operator expansion with
respect to impedance variation and allows examination of its effects and the
resulting modification of the field scattered by the rough surface. For a fixed
rough surface and randomly varying impedance, expressions are derived for the
scattered field itself, and for the coherent field with respect to impedance
variation for both flat and rough surfaces in the form of effective impedance
conditions
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Recovery of rough surface in ducting medium from grazing angle scattered wave
A method is developed for rough surface reconstruction using fields scattered at grazing angles in a medium with a linearly varying refractive index and Neumann boundary condition. This regime represents a ducting medium, bounded by a perfectly conducting surface with a TM incident field or an acoustically hard surface. This significantly extends the iterated marching method, based upon the parabolic integral equation for forward-scattered field components [Chen and Spivack, J. Opt. Soc. Am. A 35, 504–513 (2018)]. The approach, which uses a fixed frequency, is able to accurately recover multiscale surfaces and is found to be robust with respect to measurement noise and localized perturbations.</jats:p
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Statistical moments for rough surface scatter from two-way parabolic integral equation at low grazing angles
The moments of a plane wave scattered at low grazing angles from a one-dimensional perfectly reflecting rough surface are considered. The mean intensity and autocorrelation of the scattered field and the corresponding angular spectrum are obtained to second order in surface height. The derivations are based on an operator expansion of the extended (two-way) parabolic integral equation solution. The resulting operator series describes successively higher-order surface interactions between forward and backward going components. The expressions derived may be regarded as backscatter corrections to those obtained via the standard (one-way) parabolic integral equation method
Recommended from our members
Random scattering by rough surfaces with spatially varying impedance
A method is given for evaluating electromagnetic scattering by an irregular
surface with spatially-varying impedance. This uses an operator expansion with
respect to impedance variation and allows examination of its effects and the
resulting modification of the field scattered by the rough surface. For a fixed
rough surface and randomly varying impedance, expressions are derived for the
scattered field itself, and for the coherent field with respect to impedance
variation for both flat and rough surfaces in the form of effective impedance
conditions
Classical dynamics of electron and positron impact processes
The classical dynamics of electron and positron scattering by a hydrogen target is studied for a wide range of energies. The three-body system is integrated numerically using a regularising transformation which eliminates the Coulomb singularities of the two-body interactions. The classical mechanism of ionization is studied and some comparisons with quantum dynamics are given. Cross sections are obtained using Monte Carlo calculations with uniformly distributed initial conditions of the bound orbits. Good agreement between our classical numerical calculations and experimental results is found for total ionization cross sections, for both electron and positron scattering