Abstract :
[en] Knowing how the solution to time-harmonic wave scattering problems depends on medium properties and boundary conditions is pivotal in wave-based inverse problems, e.g. for imaging. This paper is devoted to the exposition of a computationally efficient method, called the adjoint state method, that allows to quantify the influence of media properties, directly and through boundary conditions, in the study of acoustic, electromagnetic and elastic time-harmonic waves. Firstly, the adjoint state method is derived for general boundary value problems. A continuous (rather than discrete) formalism is adopted in order to highlight the role of the boundary terms. Then, the method is applied systematically to acoustic, electromagnetic and elastic scattering problems with impedance boundary conditions, making use of the similitude between the three problems. Finally, numerical examples solved using the finite element method are presented to demonstrate the validity of the proposed method.
Funding text :
This research was funded by the Fonds de la Recherche Scientifique de Belgique (F.R.S.-FNRS) and the ARC grant for Concerted Research Actions (ARC WAVES 15/19-03 ), financed by the Wallonia-Brussels Federation of Belgium . The authors acknowledge the use of the computational resources provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifique de Belgique (F.R.S.-FNRS) and by the Walloon Region .
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