Adaptive finite element for semi-linear convection-diffusion problems

In this article a strategy of adaptive finite element for semi-linear problems, based on minimizing a residual-type estimator, is reported. We get an a posteriori error estimate which is asymptotically exact when the mesh size h tends to zero. By considering a model problem, the quality of this estimator is checked. It is numerically shown that without constraint on the mesh size h, the efficiency of the a posteriori error estimate can fail dramatically. This phenomenon is analysed and an algorithm which equidistributes the local estimators under the constraint h less than or equal to h(max) is proposed. This algorithm allows to improve the computed solution for semi-linear convection-diffusion problems, and can be used for stabilizing the Lagrange finite element method for linear convection-diffusion problems.