Two-grid finite element formulations of the incompressible Navier-Stokes equations

The paper compares two different two-grid finite element formulations applied to the Navier–Stokes equations, namely a multigrid and a mixed or composite formulation. In the latter case the pressure is interpolated on a coarser grid than the velocity, using mixed elements instead of mixed interpolation functions. In the multigrid formulation an equal-order interpolation is used on the same elements. A pressure Poisson formulation is used in both cases. Computational results are presented to compare the methods and comparisons are also made with other results.