Associated Project 7 • Wave propagation in 3D bi-periodic structures

Bi-periodic structure
This project is devoted to the investigation of time-harmonic acoustic scattering problems with (locally perturbed) periodic inhomogeneous layers above impenetrable plates in three dimensional spaces. The scattering problems are modelled by Helmholtz equations in unbounded domains, both the theoretical analysis and the numerical solution of which are very challenging.
The main tool involved nullin this project is the Floquet-Bloch transform, which has been proven to be very powerful for scattering problems with periodic structures in two dimensional spaces. The first objective is to analyze continuity and regularity of the Bloch transformed field with respect to the quasi-periodicity parameter, where the Dirichlet-to-Neumann map plays an important role.
Bi-periodic structure
The second goal is to propose a high order numerical method for scattering problems with periodic layers, based on the regularity results established for the quasi-periodic Bloch transformed problems. In contrast to the 2D case, the singularities of the Bloch transformed fields are no longer localized in a finite number of points, but cover a union of singular circles. Thus a straightforward extension of the high order numerical method for the 2D case may not be appropriate for the 3D case, and new ideas will be required. The third goal is to develop an efficient numerical method for locally perturbed periodic layers. Either a coupled finite element method or a discretization of the Lippmann-Schwinger equation will be applied.


  1. . Numerical methods for scattering problems in periodic waveguides. Numer. Math., 148(4):959–996, August . URL [preprint] [bibtex]

  2. . Spectrum decomposition of translation operators in periodic waveguide. SIAM J. Appl. Math., 81(1):233–257, February . URL [bibtex]

  3. and . Near-field imaging of locally perturbed periodic surfaces. Inverse Problems, 35(11):114003, October . URL [preprint] [bibtex]


  1. . A scattering problem for a local pertubation of an open periodic waveguide. CRC 1173 Preprint 2022/2, Karlsruhe Institute of Technology, January . [bibtex]

  2. . Exponential convergence of perfectly matched layers for scattering problems with periodic surfaces. CRC 1173 Preprint 2021/30, Karlsruhe Institute of Technology, July . [bibtex]

  3. . High order methods to simulate scattering problems in locally perturbed periodic waveguides. CRC 1173 Preprint 2021/25, Karlsruhe Institute of Technology, May . [bibtex]