GUARANTEED AND ROBUST A POSTERIORI ERROR ESTIMATES FOR SINGULARLY PERTURBED REACTION-DIFFUSION PROBLEMS

IBRAHIM CHEDDADI; RADEK FUCÍK; MARIANA I. PRIETO; MARTIN VOHRALÍK

ESAIM-MATHEMATICAL MODELLING AND NUMERICAL ANALYSIS-MODELISATION MATHEEMATIQUE ET ANALYSE NUMERIQUE

EDP Sciences

Lugar: París; Año: 2009 vol. 43 p. 867 - 888

0764-583X

We derive a posteriori error estimates for singularly perturbed reaction-diffusion problemswhich yield a guaranteed upper bound on the discretization error and are fully and easily computable. Moreover, they are also locally efficient and robust in the sense that they represent local lower bounds for the actual error, up to a generic constant independent in particular of the reaction coefficient. We present our results in the framework of the vertex-centered finite volume method but their nature is general for any conforming method, like the piecewise linear finite element one. Our estimates are based on a H(div)-conforming reconstruction of the diffusive flux in the lowest-order Raviart-Thomas space linked with mesh dual to the original simplicial one, previously introduced by the last author in the pure diffusion case. They also rely on elaborated Poincar´e, Friedrichs, and trace inequalities-based auxiliary estimates designed to cope optimally with the reaction dominance. In order to bring down the ratio of the estimated and actual overall energy error as close as possible to the optimal value of one, independently of the size of the reaction coefficient, we finally develop the ideas of local minimizations of the estimators by local modifications of the reconstructed diffusive flux. The numerical experiments presented confirm the guaranteed upper bound, robustness, and excellent efficiency of the derived estimates.