SUPERCONVERGENCE ANALYSIS OF LOW ORDER NONCONFORMING MIXED FINITE ELEMENT METHODS FOR TIME-DEPENDENT NAVIER-STOKES EQUATIONS

In this paper,the superconvergence properties of the time-dependent Navier-Stokes equations are investigated by a low order nonconforming mixed finite element method(MFEM).In terms of the integral identity technique,the superclose error estimates for both the velocity in broken H1-norm and the pressure in L2-norm are first obtained,which play a key role to bound the numerical solution in L∞-norm.Then the corresponding global superconvergence results are derived through a suitable interpolation postprocessing approach.Finally,some numerical results are provided to demonstrated the theoretical analysis.