WIAS Preprint No. 2866, (2021)

PML and high-accuracy boundary integral equation solver for wave scattering by a locally defected periodic surface



Authors

  • Yu, Xiuchen
  • Hu, Guanghui
  • Lu, Wangtao
  • Rathsfeld, Andreas

2020 Mathematics Subject Classification

  • 78A45 78M10 35J50 65R20

Keywords

  • Wave scattering, locally defected periodic surface, boundary element method, perfectly matched layer, Neumann-to-Dirichlet operator, boundary integral equations, Riccati equation, Neumann-marching operator, recursive doubling procedure

DOI

10.20347/WIAS.PREPRINT.2866

Abstract

This paper studies the perfectly-matched-layer (PML) method for wave scattering in a half space of homogeneous medium bounded by a two-dimensional, perfectly conducting, and locally defected periodic surface, and develops a high-accuracy boundary-integral-equation (BIE) solver. Along the vertical direction, we place a PML to truncate the unbounded domain onto a strip and prove that the PML solution converges to the true solution in the physical subregion of the strip with an error bounded by the reciprocal PML thickness. Laterally, we divide the unbounded strip into three regions: a region containing the defect and two semi-waveguide regions, separated by two vertical line segments. In both semi-waveguides, we prove the well-posedness of an associated scattering problem so as to well define a Neumann-to-Dirichlet (NtD) operator on the associated vertical segment. The two NtD operators, serving as exact lateral boundary conditions, reformulate the unbounded strip problem as a boundary value problem over the defected region. Due to the periodicity of the semi-waveguides, both NtD operators turn out to be closely related to a Neumann-marching operator, governed by a nonlinear Riccati equation. It is proved that the Neumann-marching operators are contracting, so that the PML solution decays exponentially fast along both lateral directions. The consequences culminate in two opposite aspects. Negatively, the PML solution cannot converge exponentially to the true solution in the whole physical region of the strip. Positively, from a numerical perspective, the Riccati equations can now be efficiently solved by a recursive doubling procedure and a high-accuracy PML-based BIE method so that the boundary value problem on the defected region can be solved efficiently and accurately. Numerical experiments demonstrate that the PML solution converges exponentially fast to the true solution in any compact subdomain of the strip.

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