A second-kind Galerkin boundary element method for scattering at composite objects

We consider the scattering of time-harmonic acoustic waves at objects composed of several homogeneous parts with different material properties. In Claeys (A single trace integral formulation of the second kind for acoustic scattering, 2011), a novel second-kind boundary integral formulation for this scattering problem was proposed, that relies on skeleton Cauchy data as unknowns. We recast it into a variational problem set in L² and investigate its Galerkin boundary element discretization from a theoretical and algorithmic point of view. Empiric studies demonstrate the competitive accuracy and superior conditioning of the new approach compared to a widely used Galerkin boundary element approach based on a first-kind boundary integral formulation.