A posteriori error estimator for obstacle problems
Project manager:  Prof. Dr. rer. nat. B.I. Wohlmuth 
Projektbearbeiter:  Dipl.. Math. A. Weiß 
Project description
In this project, we consider error estimators for obstacle problems. The focus is on error estimators which are defined in terms of H(div) conforming stress approximations and equilibrated fluxes. It can be shown that the error is bounded by the estimator with a constant one plus a higher order data oscillation term plus a term arising from the contact that is shown numerically to be of higher order. Moreover bounds for the Lagrange multiplier and efficiency of the estimator are derived.Problem with exact solution, error decay and ration between estimated and exact error 
Problem with exact solution: grid at level 2,4,6, active nodes and exact contact set (red) 
Low regularity problem: Setting and solution for alpha=pi/6 and alpha=pi/2 

Low regularity problem: Optimal convergence by adaptive refinement 
Twomembrane + obstacle problem: Setting and solution 
Twomembrane + obstacle problem: Grid and active sets at level 3,6,9. 