Session S20 - Applied Math and Computational Methods and Analysis across the Americas

Friday, July 16, 16:30 ~ 17:00 UTC-3

Error estimates for the Scaled Boundary Finite Element Method applied to harmonic problems

Sônia Gomes

Universidade Estadual de Campinas (Unicamp), Brazil   -   This email address is being protected from spambots. You need JavaScript enabled to view it.

The Scaled Boundary Finite Element Method (SBFEM) is a technique in which approximation spaces are constructed using a semi-analytical approach. They are based on partitions of the computational domain by polygonal/polyhedral subregions, where the shape functions approximate local Dirichlet problems with piecewise polynomial trace data. Using this operator adaptation approach, and by imposing a starlike scaling requirement on the subregions, the representation of local SBFEM shape functions in radial and surface directions are obtained from eigenvalues and eigenfunctions of an ODE system, whose coefficients are determined by the element geometry and the trace polynomial spaces. For harmonic model problems, we characterize SBFEM spaces in the context of Duffy’s approximations for which a gradient-orthogonality constraint is imposed. As a consequence, the scaled boundary functions are gradient-orthogonal to any function in Duffy’s spaces vanishing at the mesh skeleton, a discrete mimetic version of a well-known property valid for harmonic functions. This orthogonality result is applied to provide a priori SBFEM error estimates in terms of known finite element interpolant errors of the exact solution. Similarities with virtual harmonic approximations are also explored for the understanding of SBFEM convergence properties. Numerical experiments with 2D and 3D polytopal meshes confirm optimal SBFEM convergence rates for test problems with smooth solutions. Attention is also paid to the approximation of a point singular solution by using SBFEM close to the singularity and finite element approximations elsewhere, revealing optimal accuracy rates of standard regular contexts

Joint work with Karolinne O. Coelho (FEC-Unicamp, Campinas, SP, Brazil) and Philippe R. B. Devloo (FEC-Unicamp, Campinas, SP, Brazil).

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