Acceleration of an iterative method for the evaluation of high-frequency multiple scattering effects

High frequency integral equation methodologies display the capability of reproducing single-scattering returns in frequency-independent computational times and employ a Neumann series formulation to handle multiple-scattering effects. This requires the solution of an enormously large number of single-scattering problems to attain a reasonable numerical accuracy in geometrically challenging configurations. Here we propose a novel and effective Krylov subspace method suitable for the use of high frequency integral equation techniques and significantly accelerates the convergence of Neumann series. We additionally complement this strategy utilizing a preconditioner based upon Kirchhoff approximations that provides a further reduction in the overall computational cost.