Bubbles Enriched Quadratic Finite Element Method for the 3D-Elliptic Obstacle Problem
This work extends optimal quadratic finite element methods from 2D to 3D for obstacle problems, addressing a gap in the literature.
The authors propose a quadratic finite element method enriched with bubble functions for the 3D elliptic obstacle problem, achieving optimal convergence rates with respect to regularity. Numerical experiments confirm the theoretical a priori error estimates.
Optimally convergent (with respect to the regularity) quadratic finite element method for two dimensional obstacle problem on simplicial meshes is studied in (Brezzi, Hager, Raviart, Numer. Math, 28:431--443, 1977). There was no analogue of a quadratic finite element method on tetrahedron meshes for three dimensional obstacle problem. In this article, a quadratic finite element enriched with element-wise bubble functions is proposed for the three dimensional elliptic obstacle problem. A priori error estimates are derived to show the optimal convergence of the method with respect to the regularity. Further a posteriori error estimates are derived to design an adaptive mesh refinement algorithm. Numerical experiment illustrating the theoretical result on {\em a priori} error estimate is presented.