TY - JOUR KW - error estimation KW - finite elements KW - adaptivity KW - fluid dynamics KW - Galerkin methods TI - Duality Based A Posteriori Error Estimation for Quasi-Periodic Solutions Using Time Averages UR - http://dx.doi.org/10.1137/100809519 SP - 2199 VL - 33 N2 - We propose an a posteriori error estimation technique for the computation of average functionals of solutions for nonlinear time dependent problems based on duality techniques. The exact solution is assumed to have a periodic or quasi-periodic behavior favoring a fixed mesh strategy in time. We show how to circumvent the need of solving time dependent dual problems. The estimator consists of an averaged residual weighted by sensitivity factors coming from a stationary dual problem and an additional averaging error term coming from nonlinearities of the operator considered. In order to illustrate this technique the resulting adaptive algorithm is applied to several model problems: a linear scalar parabolic problem with known exact solution, the nonsteady Navier?Stokes equations with known exact solution, and finally to the well-known benchmark problem for Navier?Stokes (flow behind a cylinder) in order to verify the modeling assumptions. JF - SIAM Journal on Scientific Computing EP - 2216 AV - public ID - discovery1384725 SN - 1064-8275 N1 - Copyright © 2011 Society for Industrial and Applied Mathematics A1 - Braack, M A1 - Burman, E A1 - Taschenberger, N Y1 - 2011/09/06/ IS - 5 ER -