Non-conforming Galerkin finite element methods for local absorbing boundary conditions of higher order
Résumé
A new non-conforming finite element discretization methodology for second order elliptic partial dif-
ferential equations involving higher order local absorbing boundary conditions in 2D and 3D is proposed.
The novelty of the approach lies in the application of C 0 -continuous finite element spaces, which is the
standard discretization of second order operators, to the discretization of boundary differential operators
of order four and higher. For each of these boundary operators, additional terms appear on the bound-
ary nodes in 2D and on the boundary edges in 3D, similarly to interior penalty discontinuous Galerkin
methods, which leads to a stable and consistent formulation. In this way, no auxiliary variables on the
boundary have to be introduced and trial and test functions of higher smoothness along the boundary are
not required. As a consequence, the method leads to lower computational costs for discretizations with
higher order elements and is easily integrated in high-order finite element libraries. A priori h-conver-
gence error estimates show that the method does not reduce the order of convergence compared to usual
Dirichlet, Neumann or Robin boundary conditions if the polynomial degree on the boundary is increased
simultaneously. A series of numerical experiments illustrates the utility of the method and validates the
theoretical convergence results.
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