摘要
We consider acoustic scattering of time-harmonic waves at objects composed of several homogeneous parts.Some of those may be impenetrable,giving rise to Dirichlet boundary conditions on their surfaces.We start from the recent secondkind boundary integral approach of[X.Claeys,and R.Hiptmair,and E.Spindler.A second-kind Galerkin boundary element method for scattering at composite objects.BIT Numerical Mathematics,55(1):33-57,2015]for pure transmission problems and extend it to settings with essential boundary conditions.Based on so-called global multipotentials,we derive variational second-kind boundary integral equations posed in L^(2)(S),where S denotes the union of material interfaces.To suppress spurious resonances,we introduce a combined-field version(CFIE)of our new method.Thorough numerical tests highlight the low andmesh-independent condition numbers of Galerkin matrices obtained with discontinuous piecewise polynomial boundary element spaces.They also confirm competitive accuracy of the numerical solution in comparison with the widely used first-kind single-trace approach.
基金
The authors would like to thank L.Kielhorn for his great support during the development of the code for the first-and second-kind formulation in BETL2[25]
The work of E.Spindler was partially supported by SNF under grant 20021137873/1
X.Claeys received support from the ANR Research Grant ANR-15-CE23-0017-01.
